Lungworms in Ontario dog

Another emerging infectious disease issue for the Ontario dog population appears to be lungworms. As you’d probably guess, lungworms are parasites that live in (or near) the lungs. A variety of different types of lungworms exist, but most concerns around here relate to two.

In Canada, both the fox lungworm (Crenosoma vulpis) and the French heartworm (Angiostrongylus vasorum) have been found in the Atlantic provinces for a while. However, this seems to be a new situation in Ontario, with a small but increasing number of reports of Crenosoma vulpis in dogs that have not been outside of the province. I haven’t heard about any Angiostrongylus cases in the province yet (and hope it stays that way - see why below).

Foxes are the natural reservoir of both of these lungworms. Like many parasites, lungworms have a rather bizarre life cycle. Adult Crenosoma worms live in the lungs and lay eggs. The eggs are then coughed up, swallowed and passed in feces. After being pooped out, the lungworm larvae infect snails. Dogs get infected by eating infected snails, as the larvae move from the intestinal tract and through the body to the lungs, where they mature and the whole cycle starts again.

It’s similar with Angiostrongylus, although the larvae can also infect frogs (when they feed on infected snails), and dogs can be infected by eating infected snails or frogs. After a dog swallows the larvae, they migrate into the bloodstream and make their way to the heart and arteries of the lung.

Typical signs of Crenosoma infection in dogs include a chronic or intermittent cough that’s not responsive to common treatments directed at bacterial or inflammatory diseases. Fortunately, Crenosoma infections are usually treatable with anti-parasitics, with a good outcome.

Angiostrongylus vasorum is a bigger concern, because infection can result in more severe lung disease, blood clots, heart failure and a few other bad things. Adult worms can also head to other parts of the body and cause more problems (but fortunately that's pretty uncommon).

If one or both of these parasites are established in the fox population in the province, lungworm is not going away. Understanding where it is present will be important for prompt diagnosis and to determine the best preventive medicine programs. As it stands now, lungworms have to be considered as a potential cause of chronic cough in dogs in Ontario. It’s still probably rare but is potentially treatable and something of which to be aware.


Echinococcus multilocularis...small tapeworm, big problem

Echinococcus multilocularis is causing increasing concern in Ontario lately (amongst the few people who are aware of it, at least) as there’s evidence that it may have become established in the province. This parasite is a tapeworm harboured by canids (including both domestic dogs and wild ones like coyotes and foxes), and can cause serious disease in people. It’s an insidious problem since the incubation period in humans is many years, meaning it takes a long to realize that there’s a problem.

We don’t know the status of this parasite in the province but there’s enough evidence to be concerned and look into the issue further.

If you want to learn more about it, Dr. Andrew Peregrine’s recent seminar on the topic is a great start.

Deworming wild and feral animals

I had a question the other day about roundworms in feral cats. Specifically, how do you deworm a group of cats that you don’t handle and may not be able to catch? There are a few possible approaches, from trapping and treating (oral or topical) to trying to get a dewormer into them via food. Neither is a great option in many situations, because you can't usually catch all the animals (and feral cats aren’t always the nicest to handle...), or they might not get the proper dose of drug if its given in food.

Baits are a convenient way to treat wild and feral animals, since they are easy to administer and can work quite well. Rabies vaccine baiting has been highly effective in wildlife, and a similar approach could be used for parasite control.

A recent study in Emerging Infectious Diseases (Page et al. 2014) shows the potential usefulness of dewormer baiting for control of the raccoon roundworm, Baylisascaris procyonis, in urban raccoons. The researchers made dewormer baits similar to those used for rabies vaccine, with marshmallow flavoring (don’t ask me why, but raccoons love marshmallows). They mixed a dewormer, pyrantel pamoate, with marshmallow crème, and sealed it in a hollow fishmeal polymer bait container. They then distributed baits in the vicinity of raccoon latrines in suburban Chicago and also tracked a set of untreated latrines. Fecal samples were collected from the environment before and after one year of monthly baiting.

Pre-treatment, B. procyonis was identified in 13% of samples, equally distributed between sites they subsequently baited and sites they did not bait (to act as controls).

After the one year baiting period, B. procyonis eggs were found in 21% of samples from the untreated control sites but only 3% of the treated sites.  That's a pretty dramatic (and statistically significant) difference.

This shows the potential impact of a relatively easy and cost-effective method to deworm raccoons, to reduce contamination of the environment and subsequent human exposure. It couldn’t be a one-shot deal, though. You’d never eradicate the parasite and raccoons will continue to be exposed, even if levels in latrines decrease. So, ongoing baiting would be needed to control the parasite and keep contamination down. That involves more effort and cost, but could be reasonable in high risk areas, such as parks with lots of raccoons and lots of human and pet traffic, or in other areas where elimination of latrines is not practical but there is a reasonable risk of human or domestic animal exposure.

It also raises questions about whether this might be an effective approach for feral cat colonies... stay tuned.

Lyme disease & ticks: New infosheet

The latest Worms & Germs infosheet, all about Lyme disease and ticks, is now available on the Resources - Pets page.  Although it's getting colder and occasionally snowy up in Ontario, there are lots of parts of North America where ticks are active all year round.  It's particularly important for any "snowbirds" who may travel south with their pets over the winter to be aware of the potential for exposure to ticks and the diseases they transmit (not just Lyme disease!), and to make sure their pets (as well as they themselves) are properly protected.  (The same goes for exposure to mosquitoes, which can transmit (among other things) heartworm.)

Remember that dogs (nor any other mammal for that matter) cannot transmit Borrelia burgorferi, the bacterium that causes Lyme disease, to people; however, this is a good example of a "one health" disease that clearly affects both people and animals.  Finding the disease in one species is an indication that the other is at risk as well, when there is exposure to a common source (i.e. the ticks).

Thanks to University of Guelph professor and parasitologist Dr. Andrew Perigrine for his input on the infosheet as well.

Image: A female blacklegged tick, Ixodes scapularis, engorged with a host blood meal. (Source: CDC Public Health Image Library 15993)

Raccoon roundworm reminder

An article by Dr. Ann Britton of British Columbia’s Animal Health Centre (AHC) on the blog site  is another reminder of the perils of raccoon poop. Over a 2 year period, 17 raccoons were submitted to the AHC for necropsy, and 12 (71%) of them were infected with Baylisascaris procyonis, the raccoon roundworm. The number of animals tested was small, and the number of infected raccoons is not surprising given similar results of other studies of raccoons in various areas, but it’s a good reminder that a large percentage of raccoons are infected with this parasite, and can shed massive numbers of eggs per day.

“So what?” you might say.

While human infections are very rare, they’re devastating and typically result in death or severe brain damage.

Some key points:

  • Consider all raccoons infected with roundworms, and all raccoon poop contaminated.
  • “Old” raccoon poop is the bigger concern. The roundworm eggs have to mature in the feces for a few days before they are able to infect people or other animals. However, once they’ve done that, they are very hardy and can survive for long periods of time in the environment.
  • Raccoons tend to poop in the same spot day after day. These raccoon latrines can have massive egg burdens.
  • Care should be taken when handling raccoon feces or when cleaning up a raccoon latrine. More info about cleaning up raccoon latrines can be found in a previous Worms & Germs post on this topic
  • Rarely, dogs can also become infected by the raccoon roundworm. Dogs should be kept away from raccoon latrines because of the potential for infection and (maybe of greater concern) the potential for them to carry Baylisascaris eggs into the house on their haircoat.

Click here for the full article from


All about tapeworms and Echinococcus

The latest Worms & Germs infosheets are all about some common and not-so-common members of a particular group of parasites: tapeworms. There are a number of different groups and species of tapeworms that can infect pets, people, and other domestic animals, and sorting through which is which can be tricky, so we created a Tapeworms infosheet to help sort out the details.

There is one group of tapeworms in pets that is a particular concern from a zoonotic disease perspective. These parasites belong to the genus Echinococcus. Normally these tapeworms circulate in the wildlife population, mostly in wild canids such as foxes and various prey species, but they can also affect domestic dogs (and sometimes cats) that scavenge or hunt the same prey. In most cases the pet does not become sick, but people who are exposed to the tapeworm eggs in the pet’s feces can develop slow-growing cysts known as hydatid cysts or alveolar hydatid cysts. Over time these cysts can become very large and difficult to treat. There is also now evidence that one Echinococcus species (E. multilocularis) may be spreading - in 2012 a dog in Ontario was found to be infected with the cystic form of E. multilocularis (which is unusual in itself), but the animal had no history of travel outside of the province, therefore it was most likely infected via local wildlife.

Because echinococcosis can be such a severe disease in people, we created an additional infosheet focused on just Echinococcus. Both infosheets can be found on the Worms & Germs Resources - Pets page.

Image: Dozens of Echinococcus granulosus tapeworms from the small intestine of a dog.  Although these adult tapeworms are tiny compared to some other species, this species can cause significant problems in people through the formation of hydatid cysts.  (Photo credit: Ontario Veterinary College)

Why Finnegan's an indoor cat

I grew up with cats, and they were all indoor/outdoor. I never really thought about it since that was just the way things were done. Yet, as much as he’d like to convince us otherwise, our current cat Finnegan is an indoor cat. There are a lot of reasons for this.

One reason for keeping Finnegan in the house is zoonotic disease prevention. I was recently giving a talk about "Pets and immunocompromised owners" at the American College of Veterinary Internal Medicine forum, and a recurring theme for reducing the risks associated with cats was keeping them inside. (Want to reduce the risk of the cat being exposed to Toxoplasma? Keep it inside. Want to reduce the risk of Salmonella exposure? Keep the cat inside...).

Another important reason is the animal's own health:

  • Cat vs car rarely ends well for the cat, and untold thousands of cats meet their ends on roads every year.
  • Cat vs cat isn’t as bad but can lead to cat bite abscesses and transmission of a few different pathogens such as feline immunodeficiency virus (FIV) and feline leukemia virus (FeLV).
  • When outside, cats can also be exposed to various insect borne pathogens that can be of concern. This kind of risk varies between regions, with areas such as those where there are ticks carrying Cytauxzoon felis (a parasite normally carried by bobcats) perhaps being the biggest concern.

Wildlife is another concern, in two ways. Just like with cars, cat vs larger critter such as a coyote rarely ends well for the cat. From an ecological standpoint though, greater problems occur from cats killing smaller wildlife. It’s been estimated that free-roaming domestic cats kill billions (yes, Billions) of birds and small mammals every year. I won’t go into all the details here, but there’s a good article on the Canadian Cooperative Wildlife Health Centre’s website about the impact such avid feline predators can have on local ecology.

Some people would argue that cats are better off going outside. Looking back at the cats with which I grew up, a lot died early because they were allowed to go outside. It’s hard for me to justify the risk to the cat, wildlife and public health for some anthropomorphic “he’d really enjoy being outside” argument.


Hookworm info sheet

While this morning's -7C temperature and snow don't exactly make me think about sandboxes or wandering around barefoot, warmer weather will presumably occur someday and the risk of outdoor exposure to parasites will start up again.

Since nothing says summer like hookworms, here's a new info sheet all about hookworms, including information on cutaneous larva migrans. The sheet can also be found on the Worms & Germs Resources - Pets page, along with info sheets on many other topics.

What does a puppy have to do with herd health?

The new puppy, now named Merlin, is keeping things busy around here. (Note to self: avoid getting a new puppy during miserable weather.  Standing in pouring, driving rain at 4 AM is not fun. Okay, enough whining.)

Yesterday, I wrote about the new puppy's deworming plan. One thing I forgot to mention was the rest of the "herd." By that, I mean Meg, our 11-year-old Lab. Herd health gets a lot of attention in food animals and to a lesser degree in horses, but many concepts remain important for pets. Specifically, when you introduce a new member into the herd, you might change disease risks or required preventive measures for other members of the herd.

Meg lives a pretty cat-like existence. She sleeps, eats, walks far enough to go outside to pee and, well, that's about it. As an older dog who has very rare contact with other dogs, her risk of exposure to many microorganisms, such as parasites, is limited. However, since we brought a new little furry vector into the house, Meg might be exposed to some things that haven't been much of a concern in the past. Her habit of eating whatever she can find (including poop), increases that risk further. So, what's the herd health plan?

It's not too detailed, actually.

  • One thing is making sure that we deworm Meg and we don't just focus on the puppy. She might be exposed to anything the puppy is/was shedding. We're usually pretty lax on deworming her in the winter months, but she'll get a couple of doses of dewormer alongside the puppy. 
  • Poop removal. Since Meg's a notorious poop-eater, we'll want to remove Merlin's waste promptly. That's pretty straightforward. If she can't find it, she can't eat it. It's also important to make sure that old feces aren't left around, because some parasites require time in the environment to become infectious, so regular feces removal prevents accumulation of infective forms of some. The current temperature is at the lower limit of where Toxocara eggs are able to develop into infectious larvae, and the risk will probably be pretty minimal as the temperature drops over the next few days, but it's not hard to make sure the yard gets cleaned up.
  • If we find something in the puppy, then we'll have to consider whether Meg might be exposed or at risk too, and decide whether she needs to be tested or treated.

The other aspect of the herd is the non-canine component of the household (i.e. the kids). The key points for that, in terms of zoonotic parasites, are cleaning up feces from the yard, avoiding fecal contact, hand washing, treating the dogs appropriately to reduce parasite shedding and other basic feces-avoidance measures.

New arrival...

Hide the kids’ toys, tune up the carpet cleaner, get ready for some sleep deprivation… there’s a new dog in the house. Last night, the yet-to-be-named ("he who shall not be named" having been rejected by Heather) little yellow critter arrived. Meg (the existing dog) seems relatively content, or at least resigned. The cat... not so much, but he's already established who's the boss.

So, while I'm momentarily not trying to convince the puppy to pee outside, I’ll take this opportunity to hopefully practice what I preach and describe what we’re doing for things like vaccination, deworming and other infectious disease-related topics.

To start things off: What’s the deworming plan?

  • Roundworms (Toxocara canis) are the main concern in puppies. It’s generally a good idea to assume that a young puppy has roundworms, regardless of from where it came and how well cared for it was.
  • Canadian parasite treatment guidelines are to treat puppies with a drug that will kill Toxocara worms at 2, 4, 6 and 8 weeks of age, then monthly until 6 months of age. Our little guy is 9 weeks old and has already been treated a couple of times for roundworms, plus he's had one treatment for coccidia (a different parasite that was found on a recent fecal exam).  He’ll get another dose of pyrantel pamoate in the next day or two, then monthly until he’s 6 months old. (If someone gets a puppy and it hasn’t been treated like this or its vaccination history isn’t known, it is recommended to give 3 treatments 2 weeks apart, then monthly until 6 months).
  • A fecal exam will be done on the puppy in the near future. It’s not an emergency since it won’t impact what I do at the moment in terms of treatment, but it’s good to see if there are any parasites that aren’t killed by the chosen dewormer (e.g. tapeworms) and to detect resistant parasites (i.e. Toxocara eggs still found in feces after appropriate treatment).
  • No flea treatment now since he doesn’t have any evidence of a flea infestation and it’s not very likely he’ll be exposed to fleas before the spring based on the current climate where we are.
  • No heartworm treatment until the spring either. The Canadian Parasitology Expert Panel (CPEP) recommentaion is for dogs to receive monthly heartworm preventive treatments beginning at a maximum of two months of age. So, I’m not really following that one, but given the time of year, the low prevalence of heartworm in the area he's from and the fact that the puppy wouldn’t have had too much risk of mosquito exposure because of its age and indoor housing, the risk of heartworm exposure this season is very low.

More updates to come, and hopefully not too many descriptions of how to clean puppy feces off of various surfaces.


Identifying the "right" parasite control program

Here is another guest blog, this time from the "worm-guy" Dr. Martin Nielsen of the Gluck Equine Research Center at the University of Kentucky.

At the recent 9th International Conference on Equine Infectious Diseases (EIDC) in Lexington, Kentucky several sessions were focused on parasite control of horses. Drug resistant parasites are a world-wide problem in equine establishments, and it has become a challenge to define a simple and useful set of guidelines to be used by horse owners. As many readers of the Worms & Germs Blog will be aware, there is no longer a “one size fits all” program, and parasitologists instead often talk about the complexity related to the different parasites that often infect the horses in concert, their interactions with their hosts, and how to interpret fecal egg counts. While this is all useful and important information, it can be frustrating when it does not readily come with some practical guidance.

Equine parasitology is rarely well-represented at parasitology conferences. Usually, there are less than a handful equine abstracts, and often not even enough for a separate session. The three or so participating equine parasitologists often have to create their own little scientific session over a cup of coffee during the breaks. The EIDC was much different. It had participation from leading equine parasitologists from Sweden, Denmark, Finland, Germany, United Kingdom, Canada, Brazil, and the USA. More than 30 parasitology abstracts were presented at the meeting, and a special session critically addressed the most pressing research needs for equine parasite control. During the conference, an international equine parasitology consortium was formed, and it will serve to coordinate future research efforts and to communicate consensus-based guidelines for parasite control.

So, what are these recommendations then?  New research presented at the EIDC illustrated very well that general recommendations are more straight-forward than often anticipated. Work performed by Kurt Pfister and colleagues in Germany illustrated that fecal egg counts are useful for monitoring and controlling parasite transmission by the means of selective therapy. Two Danish studies illustrated that one or two yearly strategic treatments applied to all horses are advisable to effectively break the life cycle of large strongyles, particularly the bloodworm, Strongylus vulgaris. In other words, a basic foundation of treatments can be defined, upon which the some of the more parasitized horses can be identified to receive additional treatments with a selective approach. Several presentations underlined the need for yearly routine evaluations of the efficacy of the anthelmintic drugs used on each farm. The fecal egg count reduction test is the most important use of the fecal egg counts. [Weese comment: that's when you do a fecal egg count before and after deworming, and compare the egg counts to see how much they dropped, as an indication of how well the dewormer worked] Perhaps most encouraging was the promising new diagnostic tools presented by several groups for detection of migrating or encysted parasite larvae. These will turn very useful for identifying horses at risk of disease and in need of deworming. One of these, developed by Jacqui Matthews and her group at Moredun Research Institute in Scotland shows great promise for measuring burdens of small strongyle larvae (cyathostomins), which can pose a threat for severe parasitic disease. With these new tools in hand, we will become able to further refine our recommendations in the future.

Echinococcus in Canada

If you ask people about tapeworms, they typically think about the "ick" factor of having a  large worm in their gut, but they probably don't get too concerned. However, some types of tapeworm infection can be serious health problems in humans and animals. One of the worst is infection by the tapeworm species Echinococcus multilocularis. A couple of recent reports about E. multilocularis in Canada have received a lot of attention.

With Echinococcus, the problem isn't the worm living in the intestine. Adult worms live in the intestinal tract of only "definitive hosts," which are primarily foxes and coyotes in North America. The worms aren't necessarily a problem for these animals, but they can pass large numbers of tapeworm eggs in their stool. The parasite's normal life cycle continues when small animals (e.g. rodents like mice and voles) swallow a tapeworm egg. The parasite then develops into a cyst in the animal's body, and if/when the little critter is eaten by a fox or coyote, the cyst gets eaten too and the fox/coyote develops a new adult tapeworm in the intestinal tract.

When it comes to people (and some other domestic species), the problem is what happens when they ingest tapeworm eggs. Like in rodents, the eggs hatch and the immature parasites migrate through the intestinal wall, and can then spread to virtually any place in the body. They can then develop into large cysts that, over a long period of time, result in serious disease. Large cysts and/or cysts in critical areas (e.g. the brain) can be devastating. Treatment is difficult, prolonged and expensive, and death rates are high.

Dogs are a bit of an oddity in this cycle, since they can carry adult tapeworms (not surprising, since they are similar to foxes and coyotes) but they can also get these large tissue cysts. From public health and infection control standpoints, dogs shedding Echinococcus eggs are the main concern, but cysts are potentially devastating in the rare dog that develops one, just as they are in people.

Recent concerns revolve around two papers, one that described a dog from British Columbia with Echinococcus cysts (Jenkins et al. Emerging Infectious Diseases 2012) and a study that identified E. multilocularis eggs in feces from 23/91 (25%) urban coyotes in Alberta (Catalano et al. Emerging Infectious Diseases 2012).

What's the risk in Canada?

It's low.  Actually it's very low, and there have been only a handful of cases diagnosed even in people in North America. But with a serious disease like this, you can't ignore it. If Echinococcus is spreading in coyotes and foxes, it creates the potential for exposure of other species (including humans). The risk gets higher as coyotes and foxes get closer and closer to people and dogs, as is happening in some areas because of urban sprawl. The more coyotes that are around and the closer they are to human populations, the greater the chance that a person or dog will inadvertently ingest a tapeworm egg from coyote feces. Dog parks may be of particular concern because of the high traffic through them and the potential for them to be a big mixing site between wildlife, pets and humans.

There shouldn't be any panic because of this, as it still remains an extremely rare disease. But, it's not much consolation that it's a rare disease if you're the one with a big Echinococcus cyst in the brain. So, while the risk is low, we don't really know (yet) whether it's changing, and it's worth using some basic practices to reduce the risk. These include:

  • The standard: Don't eat poop. Pretty straightforward but easier said than done, in many respects, since fecal contamination of the environment is pretty common. Avoiding inadvertent ingestion of feces can be done through proper handling of dog and wildlife feces and attention to handwashing.
  • Controlling rodents and preventing pets from catching and eating rodents.
  • Preventing dogs from eating wildlife feces.
  • Routine tapeworm deworming should kill Echinococcus and if a dog is at particularly high risk, more regular testing and treatment for tapeworms may be indicated. Not many dogs fit into that category at the moment, though.

Image: Echinococcus multilocularis isolated from a fox in Hungary.  Unlike the very long tapeworms of the Taenia genus, which are most commonly found in dogs and cats, Echinococcus tapeworms are quite small (the bar in the picture is 0.5 mm), but the eggs shed in the feces of animals with an intestinal infection (involving mature adult worms) are virtually identical to those of Taenia spp. (click image for source).

Flea collar withdrawal in France

A group of flea (or flea and tick) collars have been removed from the market in France following a risk assessment. The review looked at these widely available, over-the-counter products that contain a variety of different chemicals. The determination was that the risks posed by contact with the collars (particularly to children) were unacceptable compared to the benefits.

As with most risk assessments, cost-benefit is the key. With flea collars, you have something containing a chemical that's easily (and commonly) touched by people, and you also have the potential that young children could put them in their mouths. That's the "cost" aspect. The beneficial side is two-pronged. One consideration is the importance of flea and tick control to human and/or animal health. That's certainly significant, since fleas and ticks can be associated with various problems, including infectious diseases and flea allergies. However, the other consideration is whether there are safer and/or more effective alternatives. The answer to that is yes - there are now much better approaches for flea and tick control than flea collars in terms of effectiveness and safety. The disadvantage is that these alternatives are somewhat more expensive and not available over the counter, but the cost and logistics are far from cumbersome.

So, the withdrawal of the flea collars from the market in France is a very reasonable move, and one that needs to be accompanied by information to pet owners that emphasizes that:

  • yes, flea and tick control are still important.
  • there are much more effective options that are safer for the pet and the family.
  • people should work with their veterinarian to determine the approach that best fits their pet(s) and family.

Toxoplasma risk factors for cats

There's been a lot of publicity (aka hype bordering on paranoia, including a recent article in the Toronto Star) about the cat-associated parasite Toxoplasma gondii lately. Cats are the definitive host of this parasite and it can cause serious disease in certain people: in pregnant women who have not been previously exposed to the parasite it can infect the unborn fetus, and it can cause severe illness (including neurological disease) in people with severely compromised immune systems. It's also been very loosely implicated in various other conditions, but much of the information gets overblown, as there is lack of solid evidence of a role of Toxoplasma in most of these cases.  Unfortunately, cats end up getting a bum rap in the process, even though most Toxoplasma infections don't come directly from cats.

Nonetheless, toxoplasmosis is a potentially devastating disease in some circumstances. and taking measures to reduce exposure to the parasite makes sense. To do this you need to know what makes cats more likely to be infected, so that these factors can be modified. A recent paper in Preventive Veterinary Medicine (Opsteegh et al. 2012) investigated risk factors for cats having antibodies against Toxoplasma. It's important to note that the presence of antibodies means the cat was exposed at some point and mounted an immune response, not that it's currently shedding the parasite in its feces. Most cats only shed Toxoplasma in their feces for a very short window of time (a week or two) after initial exposure, and that usually occurs early in life. Therefore, it's rare for older cats in households to be shedding the parasite.

The research group found 18% of cats they tested had antibodies against Toxoplasma, and they identified a few factors associated with previous Toxoplasma infection:

  • Age: Younger cats were less likely to have antibodies. The likelihood of having Toxoplasma antibodies increased steadily from 1-4 years of age.
  • Hunting
  • Presence of a dog in the house
  • Being a former stray
  • Feeding raw meat

Most of these make perfect sense and are consistent with other studies. Cats typically get infected by ingesting Toxoplasma cysts found in the muscle of other animals. So, cats that are outside (indoor/outdoor cats, former strays) and hunt, or cats that are fed raw meat are more likely to be exposed. Analysis of the data indicated that hunting contributed the most.

So, while the risk of Toxoplasma infection for the average person is pretty low, some basic management practices can further reduce any risk:

  • Keep cats indoors: This greatly reduces the chance they will be exposed to the parasite. It is also good idea for several other reasons.
  • Don't feed cats raw meat: Cooking meat to the recommended temperature and time will kill any encysted parasites - this also helps prevent exposure of people eating the meat (to Toxoplasma and lots of other bacteria).
  • Control rodents in the house (not by getting a cat!): Indoor cats can still be exposed to various infectious agents through catching mice. I know it's not always easy or even possible (my cat still catches the odd indoor critter) but taking measures to reduce the likelihood of this is wise.

Other important preventive measures include:

  • Changing the litterbox regularly, especially if a high-risk person has to do it. Toxoplasma oocysts need at least 24-48h in the environment to become infective. If feces are removed daily, they don't get that chance.
  • Clean up any fecal accidents and remove any fecal staining of the haircoat (e.g. poop stuck around the rear end of long-haired cats) promptly, before that 24-48h window expires.
  • Wash you hands regularly, especially after contact with the litterbox or any potentially contaminated areas.
  • Wash vegetables and cook meat properly. You're more likely to get Toxoplasma from food than from your cat.

More information about Toxoplasma can be found on the Worms & Germs Resources page.

Shelter Giardia outbreak from birds?

The Redlands Animal Shelter in California is looking into bird control measures after blaming Giardia infections in dogs on exposure to wild bird poop. On Facebook, Redlands Friends of Shelter Animals have declared "We have a serious problem with birds at the shelter. They land on the kennels and poop goes into the water bowls and give the dogs giardia - which is a parasite that gives them explosive diarrhea."

Giardia is a protozoal parasite that can cause diarrhea in dogs and other species. It can also be carried by healthy dogs, at relatively high rates in some groups. The scope of the problem at the Redlands shelter isn't clear since the news article only talks about one case. Whatever the scope, shelter management is blaming the birds.

Apparently, discussions are underway with different companies about a solution to the bird problem, something that is anticipated to be expensive. However, it's all too common for people to jump the gun on expensive interventions when there's an outbreak and overlook the root causes. While news reports don't always give the whole story, I'd be wary about blaming birds without much more evidence.

Can wild birds carry Giardia? Yes. However, there's more to the Giardia story than that. It doesn't sound like they've actually tested the bird feces to determine whether Giardia is there. Additionally (and critically) it doesn't sound like they've determined the type of Giardia that's infecting the dogs. There are different types (assemblages) of Giardia and most have a limited range of species they can infect. The vast majority of dogs with Giardia in most regions are infected by Assemblage D, a dog-specific strain that comes from other dogs and poses no risk to people. I'm not aware of Assemblage D being found in birds. Dogs can also be infected by Assemblage A, a type that infects people, and also can infect birds.

So, if Assemblage D is involved, they need to look at transmission between dogs within the shelter. If Assemblage A is involved, they still need to focus on dogs but could investigate birds as a potential source.

Overall, Giardia transmission is much more likely due to breakdowns in cleaning, disinfection, hand hygiene and general shelter practices rather than birds pooping in water bowls. It's a lot cheaper to address these shelter management practices (which will also help control various other infectious diseases) rather than dumping a lot of money into controlling bird exposure when in fact that may not be causing the problem. Trying to reduce exposure to bird poop is a good thing as a general practice, but it's important to focus efforts and resources on finding and addressing the true root problems during an outbreak. 

More information about Giardia can be found on the Worms & Germs Resources page.

Raccoon invaders and roundworms

Here’s a recent question I received:

 "My problem is that the raccoon broke a window, came into my house, ate the cat food and then defecated on the kitchen floor. Since they went a day without food, the cats may have eaten the few bits of food that were left behind. How can I tell if they got the roundworm?"

It’s a reasonable question given the concerns about Baylisascaris procyonis, the raccoon roundworm. However, there’s basically no risk. While it is very likely that the raccoons were shedding roundworm eggs in their feces, those eggs are not immediately infective. Ingesting a "fresh" roundworm egg isn't a risk. Eggs have to sit around in the environment for at least 11 days (typically 14-28 days) before they become infective. Therefore, unless the feces are allowed to sit around in the house for a couple of weeks, roundworm infection isn’t a concern in such a case.

Infection from raccoon to parrot

An article in the May/June edition of Canadian Vet Newsmagazine (a magazine, not to be confused with Canadian Veterinary Journal, a scientific journal), described an interesting case of an indoor pet bird acquiring an infection from a wild raccoon, despite no direct contact.

The bird was an African Grey Parrot that was admitted to the Ontario Veterinary College because it had developed neurological abnormalities over the preceding few weeks: a head tilt, unsteadiness and problems climbing. Infection of the brain caused by the raccoon roundworm Baylisascaris procyonis was suspected and treatment was started, however unfortunately (but not surprisingly) the bird continued to deteriorate and was eventually euthanized. Baylisascaris infection was confirmed at necropsy.

Baylisascaris procyonis, the raccoon roundworm, is extremely common in raccoons, with the majority of raccoons in some areas shedding the eggs of this parasite in their feces. The eggs are extremely hardy and can survive for long periods of time in the environment. The tendency of raccoons to defecate in the same areas (raccoon latrines) means that very high concentrations of eggs can be found in some spots. While this is a raccoon-origin parasite, it can occasionally cause infection in other species (including people and dogs, albeit very rarely). After ingestion of the parasite eggs, the eggs hatch and parasite larvae migrate through the body, causing damage to various tissues as they go. If they migrate through the brain, severe neurological disease can occur.

An interesting aspect of this case is the fact that it was an indoor parrot. If this was a dog that had been exposed to a raccoon latrine, while it would have been a rare occurrence of disease, the origin of infection would have made sense. Here, the parasite eggs had to somehow make it into the house and then into the parrot. The suspected source was branches that were collected from the backyard and placed in the bird's cage. The branches were presumably contaminated with Baylisascaris eggs, and the bird ingested some while chewing on the branches.

This is a very rare situation, but the article includes some basic recommendations:

  • Never adopt a raccoon (for many reasons beyond the Baylisascaris risk to pet birds).
  • Don't keep parrots in outdoor enclosures where raccoons have access.
  • Don't put parrots in outdoor enclosures that may have previously housed raccoons.
  • Avoid putting objects from raccoon-inhabited areas into parrot cages or treat them to kill eggs. Heating objects to 62C for 1 minute should kill any eggs that are present.
  • Ensure that cage bedding and bird feed are not potentially contaminated with raccoon feces.

(click image for source)

Giardia in dogs and cats in Ontario

Dr. Andrew Peregrine, a veterinary parasitologist at the Ontario Veterinary College, presented some data about the types of Giardia found in dogs and cats in Ontario at this week's University of Guelph Centre for Public Health and Zoonoses annual meeting.

A lot of attention has been paid to Giardia types in recent years. That's because, contrary to earlier thoughts, it's now known that certain types (also called assemblages) of Giardia can infect multiple species while others are host specific (i.e. they only infect one species). This is very important because if a dog or cat is shedding Giardia in their stool, the type determines whether there is any risk to people.

In the Ontario study, 75 canine and 13 feline Giardia-positive fecal samples were typed. In canine samples, assemblage D accounted for 68% of samples, while assemblage C accounted for 31%. These two are dog-specific, meaning 99% of typed canine samples contained only dog-specific types and were therefore no risk to human health. The other sample contained assemblage B, a zoonotic type that infects humans and animals. In contrast, 13/13 of the feline samples were assemblage A, a zoonotic type of Giardia.

These recent Ontario data indicate a low risk of transmission of Giardia from dogs to people, but some risk from cats - at least in Ontario. It's important to note that there appears to be geographic variation in this trend. Other recent studies have reported similar results, with the predominance of dog-specific types in dogs. However, a few studies have shown a predominance of the zoonotic assemblage A in dogs. These have mainly been in low socioeconomic status areas with infrastructure challenges that could increase the chance of dogs being exposed to human feces. Therefore, it may be that in areas where there is good sanitation, dogs are most likely to get Giardia from other dogs. When there are sanitation challenges, dogs may be more likely to be exposed to human types. So, it's important to know trends in different geographic regions to understand the risk of transmission from pets to humans.

Travel, pets and infectious disease risks

An important concept when dealing with infectious diseases is consideration of the risk that an animal has been, or will be, exposed to a particular microorganism. Some diseases vary greatly geographically, and something that's very important in one region may be rare or non-existent in another. Good veterinarians are aware of disease trends in their area and make informed decisions about vaccination and anti-parasitic treatments based on what's happening in the area. They also know which diseases are common and which are rare or non-existent.

But that only works if the pets stay in their "home" area. Traveling with pets can result in exposure to various infectious diseases they wouldn't normally encounter. If a veterinarian doesn't know a pet travels, they can't make proper recommendations for preventive medicine.

Additionally, travel history can be very important when evaluating a sick animal, since there may be diseases that need to be considered in a traveling pet that wouldn't be an issue with a local pet. However, it's easy to overlook or forget about travel history. Pet owners need to tell their veterinarians about "recent" travel with their pets. What does recent mean? It's hard to say. For some diseases, exposure within the past few days is all that's important. For others, it may be weeks or months. So, if you have a sick pet and have traveled any time in the past year with it, it's good to mention that to your veterinarian. It may have nothing to do with the current illness, but it never hurts to let them know anyway. In some situations, it may be the critical piece of information needed to trigger thinking about a specific disease.

Some examples of diseases that may be travel-related (at least to dogs in most parts of Ontario):

  • Blastomycosis, a fungal disease, tends to occur predominantly in specific areas. It's not too common elsewhere, but travel to high-risk areas puts blasto on the list of possibilities in certain cases.
  • Around here, there's no indication for heartworm preventive treatment during cold winter months, but that changes if the pet goes to areas where mosquitoes hang around all year.
  • Some tickborne diseases have very specific ranges that correspond to their primary hosts and certain vector species (such as birds). In Ontario, ticks are currently quite geographically focused and many dogs have little risk of exposure. Travel to one of the tick hotbed areas changes that, and means that certain tickborne diseases need to be considered.
  • Canine influenza currently seems like a non-entity in Ontario. We're still looking for it but haven't found it. It is present in some places in the US, and at times, is a big problem. Travel to a place experiencing a canine flu outbreak would be a good indication to consider canine flu vaccination.

What to do?

  • If you travel with your pet, part of your pre-travel checklist should be an appointment with your veterinarian to go over anything that needs to be done, be it vaccination, deworming, flea control, heartworm preventive or anything else. (It's also a good time to make sure there's nothing else going on with your pet, because you don't want a pet health crisis en route.)
  • If your pet gets sick and has traveled, make sure your veterinarian knows where you went and when.
  • If you travel regularly, even if it's not long distances, it's good to discuss it with your veterinarian to see if anything is required for your pet. Even if you just go a couple of hours away to a cottage regularly during the summer, you may be exposing your pet to something different.

Plague in New Mexico cat and dog

Plague has been identified in a dog and cat from New Mexico. It’s not surprising, since plague is present in some wild animal populations in that region, but it’s still noteworthy because of the serious nature of the disease and the potential for transmission to humans.

Plague is a bacterial infection caused by Yersinia pestis. It’s carried mostly be certain types of rodents in different regions of the world, including parts of the southwestern US. It’s usually spread by fleas that bite an infected rodent and then bite a person or other animal, but it can also be spread by close contact with an infected animal. Cases in cats and dogs are uncommon, but occur in areas where plague is present in rodents, when pets have contact with infected fleas or close encounters with infected rodents (or rodent carcasses).


The latest two cases were in Santa Fe and Rio Arriba Counties in New Mexico. No details were provided about the form of plague (e.g. bubonic, pneumonic), the suspected source of infection or whether there is concern about human exposure. Finding plague in a pet is a concern for a few reasons. It indicates that plague is present in wildlife in the area, and people could be exposed from the same sources as the pets (i.e. fleas, contact with live or dead wildlife). Also, transmission of plague from pets to their caretakers can occur, particularly from cats with pneumonic plague (respiratory tract infection). Knowing that a person has had contact with a pet with plague is critical to making a prompt diagnosis. According to the World Health Organization, plague continues to infect more than 2000 people every year.

The New Mexico Department of Health has made the following recommendations:

  • Avoid sick or dead rodents and rabbits, and their nests and burrows.
  • Keep your pets from roaming and hunting and talk to your veterinarian about using an appropriate flea control product.
  • Clean up areas near the house where rodents could live, such as woodpiles, brush piles, junk and abandoned vehicles.
  • Sick pets should be examined promptly by a veterinarian.
  • See your doctor about any unexplained illness involving a sudden and severe fever.
  • Put hay, wood, and compost piles as far as possible from your home.
  • Don’t leave your pet’s food and water where mice can get to it.
  • Veterinarians and their staff are at higher risk and should take precautions when seeing suspect animal plague cases.

 Photo: The vector of Yersina pestis: a flea (click image for source)

The dog in your bed probably won't kill you

A month or two ago, there was a lot of press about the risks of pets sleeping in beds. It was in response to an article in the journal Emerging Infectious Diseases that didn't put forth any new information, but summarized a few diseases that could potentially be transmitted by pets. Unfortunately, the relative risk of those diseases wasn't really explored, and some media reports latched onto diseases like the plague, transmission of which can occur between pets and humans but the likelihood of this in most areas is essentially nil.

Anyway, an article at has taken a more balanced approach towards the subject. One sentence perhaps say it best: "Many of those scare headlines, however, missed the main point of Chomel’s work: For most people, the risks are minimal, and there are easy ways to go about preventing pet-to-owner disease sharing."

I won't go into details here, since you can read the article yourself, but a key component is that pet ownership is never no-risk, but is usually low-risk. Basic hygiene practices and common sense can reduce the risks further. The cost-benefit needs to be considered, and while we can never completely eliminate the "cost" aspect, the benefits of pet ownership certainly outweigh the costs in the vast majority of households.

Resistant heartworm, cause for concern?

Heartworm is a parasitic infection (primarily of dogs) caused by Dirofilaria immitis, which is spread by mosquitoes.  In areas where the parasite is present, the standard recommendation is for preventive treatment of dogs during the mosquito season, and annual testing to make sure they don't have the disease. Numerous types of heartworm medication are available, and there's been considerable debate about the potential for emergence of heartworm resistance.

In some areas, there have been increasing numbers of reports of apparent failures of heartworm preventive medication. These cases can sometimes be explained by factors such as poor compliance (e.g. the owner forgot to give the medication or did not give it properly), unnoticed vomiting/regurgitation of oral medication, or encountering an infected mosquito outside of the normal transmission period (i.e. in areas where it's a seasonal issue and medication is therefore not given year round). However, not all cases have clear explanations, and truly resistant heartworms have been identified.

Most of the concern has been focused around the inadvertent discovery of the "MP3" strain. For companies to be able to state that their product is effective against heartworm, they have to prove it in experimental studies using recent strains of the parasite. When the MP3 strain was used to test a potential new drug, they found out that it was actually resistant to the standard treatment.

A study in Veterinary Parasitology (Blagburn et al 2011) describes further testing that was done on this strain. The authors showed that only one of the four medications tested (imidacloprid/moxidectin) provided 100% protection in experimentally infected dogs with a single treatment.

At this point, there's limited information about clinical cases of resistant heartworm, and most of the anecdotal reports come from the central US. The MP3 strain itself was found in a dog from northeast Georgia in 2006. A big question is whether this is:

  • a small, focal, regional issue
  • a regional issue that's going to expand
  • a wider but unidentified problem in many areas

There's no way to know for sure without surveillance, but it is cause for concern.

What does resistant heartworm mean to the average dog owner?

I think it means the days of being able to justify not testing dogs annually, even if it's certain that all heartworm medication has been given religiously since the last test, are over. Skipping annual testing was always a bit of a tenuous argument anyway, because of the potential for a dog to vomit or regurgitate oral medication, or to encounter an infected mosquito while not on medication, and it's even weaker now that resistance might be an issue.

Why is heartworm testing more important now?

It's important for two reasons. One is to make sure that heartworm is promptly diagnosed if it is present. This allows for earlier treatment before the parasites cause more damage. The other reason is to get information about whether resistant strains might be emerging in an area, which is helpful for the broader dog population. We have little information about the distribution of resistance, but if veterinarians start seeing heartworm cases in animals that have been properly treated with preventative medication, it's an indication that resistance might be developing in the area.

At this point, people shouldn't get too concerned about resistant heartworm, but we need to pay attention to the issue in case it increases or is in fact more widespread than we realize. Ongoing surveillance in different areas is needed to determine the scope of the problem, in terms of both the prevalence of resistant parasites and the impact on animal health. We need to be careful not to overreact, but at the same time we need to figure out what's going on. Pet owners need to have conversations with their veterinarians about the need for heartworm prevention in their pet, and the optimal approach to testing and prevention.

(click image for source)

Kinkajou owners beware

Kinkajous are strange little mammals from the Procyonidae family - the same family to which raccoons belong. Kinkajous are native to Central and South America and are occasionally kept as pets, but they don't make great pets because they are strictly nocturnal, can be cranky when woken during the day, and can sometimes be aggressive. Regardless, there is a niche pet trade, particularly in the US.

A recent report in Morbidity and Mortality Weekly Report describes detection of Baylisascaris procyonis (the raccoon roundworm) in pet kinkajous in the US, including:

  • A 10-week-old kinkajou in Tennessee in which Baylisascaris procyonis was found during a routine fecal examination.
  • Detection of Baylisascaris eggs from soil samples under the cages of a kinkajou breeder in Florida (the breeder from which the Tennessee animal was obtained).
  • An unrelated case (11 years earlier) in which adult Baylisascaris worms were found in the intestinal tract of two adult kinkajous that died of other causes.

No human infections (i.e. cases of larval migrans) were linked to infected kinkiajous.

Baylisascaris is a parasite that's extremely common in raccoons, rare (but concerning and sometimes over-hyped) in dogs, and an extremely rare cause of disease in people. While rare in humans, it still gets a lot of attention because when disease does occur, it can cause serious neurological damage, typically in children. The damage is caused by migration of parasite larvae through the body, and through the brain. This can occur after someone swallows infective parasite eggs, which then hatch in the intestinal tract and then embark on their journey through the body.

It's unclear whether Baylisascaris is a common problem in kinkajous (like it is in raccoons) or a rare finding (like it is in dogs), since this report only describes the parasite in a small number of animals, and no larger studies of intestinal parasites in kinkajous have been reported. It would be useful to know whether kinkajous are true reservoirs of this parasite (and therefore whether we should consider all kinkajous to be carriers) or whether infection is just an unusual finding.

Overall, the public health risk is likely limited.

  • There aren't that many pet kinkajous around, as far as I know.
  • While Baylisascaris is nothing to dismiss, to get infected, a person still has to eat infective eggs from feces. The likelihood of transmission from a pet to a person is therefore low if good basic hygiene measures are used.
  • The parasite eggs are not immediately infectious. They have to sit around in the environment before they are infectious, usually for 2-4 weeks. Therefore, prompt removal of feces and careful attention to basic practices like hand hygiene should greatly reduce the risk of transmission.
  • Routine testing and deworming of pet kinkajous should reduce the risk even further.

What does this mean for pet kinkajou owners? Not a lot beyond what would normally be recommended. Pet kinkajous should have good veterinary care and regular fecal examinations. Regular deworming should be discussed with the attending veterinarian, and good hygiene practices should be used to avoid contact with feces, especially old feces.

Photo credit: Robrrb at en.wikipedia

Plague in Oregon

The CDC's Morbidity and Mortality Weekly Reports has a short report about two plague cases in the US. Plague, while often thought of as a historical disease (the Black Death), is alive and well in wild rodents in some areas of the world, including parts of North America, and human cases continue to occur.

Here are highlights of the CDC report (in italics) with some extra comments.

Plague, caused by Yersinia pestis, is enzootic (present in the population, typically at a low level) among rodents in the western United States. Humans can be infected through 1) the bite of an infected flea carried by a rodent or, rarely, other animals, 2) direct contact with contaminated tissues, or 3) in rare cases, inhalation of respiratory secretions from infected persons or animals. In September 2010, the Oregon Health Authority reported the first two cases of human plague in Oregon since 1995 and the only two U.S. cases in 2010.

Both illnesses began on August 21. The patients, aged 17 and 42 years, lived in the same household and might have been exposed to plague by infected fleas from one of their dogs; that dog was found to be seropositive for Y. pestis by the passive hemagglutination-inhibition assay (dilution of 1:64). One patient acknowledged sleeping in the same bed with the dog during the 2 weeks before illness onset. Both patients had high fever and multiple bilateral inguinal buboes; one patient had hypotension, tachycardia, and acute renal failure and was hospitalized. A gram-negative rod with bipolar staining was isolated from a specimen of that patient's blood.

...25 days after specimen collection, the isolate was identified as Y. pestis... Both patients recovered uneventfully after empiric therapy with doxycycline and amoxicillin clavulanate potassium, respectively, although the latter is not considered effective in treating plague.

Plague is a Category A potential bioterrorism agent. Human infections are rare but can be life-threatening. The plague case-fatality rate depends on the clinical presentation (i.e., bubonic, septicemic, or pneumonic) and timing of antibiotic therapy initiation; if untreated, the case-fatality rate is >50% for bubonic plague and approaches 100% for pneumonic plague. Rapid laboratory identification can help guide therapy.

Sleeping in the same bed with dogs has been associated with plague in enzootic areas.  Plague patients with no history of exposure to rodents can be infected by Y. pestis if their pets carry infected rodent fleas into the home. Veterinarians always should recommend flea control to dog and cat owners.

This is an example of a situation where pets can play a role in human infection while not being the direct source of infection. While direct pet-human transmission can occur, this typically involves situations where someone has close contact with a pet that is sick with the plague. Most often, this kind of transmission is associated with close contact with cats with pneumonic (respiratory) plague.

Key aspects of reducing the risk of pet-associated plague in areas where plague is, or may be, present, are:

  • Preventing contact of pets with wildlife, living or dead.
  • Preventing roaming of pets in the wild.
  • Discouraging wildlife from living in or around homes.
  • Keeping cats indoors.
  • Routine flea control.

More information on plague and pets is available in our archives.

Chinchillas and Giardia

One concern with uncommon pets is our relatively poor understanding of the infectious agents they may carry. For our "established" pet species, we have a reasonable understanding of what bugs tend to be present and which animals may be at higher risk. The less common the pet, the less research tends to be available, making it harder to assess risks and determine what types of prevention programs need to be in place.

A recent study published in Veterinary Parasitology (Levecke et al. 2010) provides information about chinchillas and the parasite Giardia. This Belgian study involved collection of stool samples from 80 healthy pet chinchillas from 4 households and 4 breeders. They identified Giardia in a rather astounding 66% of samples. Young animals were more likely to be infected, as were animals that participated in shows (I didn't realize there were chinchilla shows).

A subset of samples were typed using molecular techniques to determine the Assemblage (strain/type) of the Giardia. This is very important from a human health standpoint, because some types of Giardia can infect both animals and humans, while others are more host-specific.  Most samples (86%) contained Assemblage B. However, a combination of different Assemblages was common, and Assemblages C (71%), A (52%) and E (9.5%) were also found. Importantly, all positive samples contained at least one of Assemblages A or B, which are types that can cause disease in people.  Assemblage C is typically associated with dogs and Assemblage E with livestock, so those results were a little surprising.

What does this tell us? It tells us that a large percentage of healthy chinchillas may be shedding Giardia in their stool, and that they typically shed types that can cause disease in people.

Does this mean people are getting sick from pet chinchillas? Not necessarily, but it indicates there is a risk.

What can chinchilla owners do? It's pretty straightforward. Giardia has to go from the animal's stool to a person's mouth to cause infection. The use of good general management and hygiene practices (especially handwashing) should greatly reduce the risks. As the folks at Barfblog say, "don't eat poop."

Should chinchillas be tested for Giardia? Probably not. A single negative result does not necessarily mean Giardia isn't there or that it never will be. Given the numbers reported here, it's best to go on the assumption that every chinchilla is (or could be) positive, and take appropriate precautions.

(click image for source)

Reducing risks with raccoon latrines

An interesting paper in the journal Emerging Infectious Diseases (Page et al. 2011) describes an impressively large effort to study the effect of anthelmintic (dewormer) baiting on parasite contamination at raccoon latrines sites in Indiana.

Raccoon latrines can be highly contaminated with various parasites, because raccoons congregate at these sites and use them as "communal toilets." Of all these parasites, the raccoon roundworm, Baylisascaris procyonis, gets the most attention.  It is very common in raccoons, but it is also a very rare cause of disease in people who swallow the infective parasite eggs from the environment.  In some of these people the parasite larvae can cause very serious neurological disease which can be very difficult to treat.

In this study, the research team identified 559 raccoon latrines in north-central Indiana. They removed debris from the areas and used a torch to help kill the parasite eggs that were there (this is one of the very few effective ways to kill the very hardy eggs of Baylisascaris). At a selection of latrine sites, they also collected baseline fecal samples. After this was all done, they distributed dewormer (pyrantel pamoate) baits in half the areas once a month (leaving the other half of the areas as controls). They then collected fecal samples at all the latrine sites approximately 6, 12 and 18 months later.

Fecal samples were tested for B. procyonis eggs. Also, they captured mice from some of the study patches. Like people, mice are intermediate hosts for B. procyonis, and they can be infected in the same manner, so researchers looked for B. procyonis larvae in the brains of the mice.

Overall, they tested 1797 fecal samples. In the first round of sampling, 33% of samples contained B. procyonis eggs. The prevalence of eggs decreases significantly (3-fold) after baiting by the first recheck, and stayed at that level throughout the study. By the one-year sample time, there was also a significant decline in B. procyonis larvae in the brains of mice (27% vs 38%).

This impressive study shows the potential impact of controlled and somewhat practical interventions on the presence of some concerning microorganisms. Certainly, no one is going to be able to treat all raccoon latrines with a torch. However, dewormer baiting might be a consideration in areas that are close to human populations, along with other control measures. Dewormer baiting could be relatively cost-effective in this case. It won't eliminate the problem, but it might help reduce environmental contamination and the associated potential for human and domestic animal exposure.

More information about Baylisascaris and raccoon latrines is available in our archives.

Miami Beach's Cat Poop Map

Miami Beach officials, disturbed by reports of a hookworm outbreak, have taken a rather unique approach to the problem: they've created a cat and cat poop map.

This fall, several cases of cutaneous larval migrans were reported - and highly publicized - in the Miami Beach area, something that is of particular concern for a tourist city that doesn't want people thinking the city's beaches are biohazardous.

Cutaneous larval migrans is a skin condition caused by migration of hookworm larvae through the skin. Dogs and cats can be carries of hookworms and pass eggs in their feces. Larvae then hatch from these eggs and can penetrate the skin (of people and animals alike) after being in the environment for a few (usually 2-9) days. If someone has contact with infectious larvae, such as by stepping on them while bare foot on a beach, the larvae get into their skin and start migrating, causing this very itchy skin condition.

Feral (stray) cats are the main problem in Miami Beach. Stray cats and beaches are a bad combination, since stray cats tend to have high rates of hookworm carriage, they often defecate in sand on the beach, and of course people often have direct contact between bare skin and beach sand. Identifying where stray cats live (and poop) is important for disease control and public education. "We needed to identify where the cats are eating — and where they're pooping — to address this problem" stated a program organizer. To do this, city sanitation workers were given GPS devices and instructions to go find cats. Data were uploaded into a mapping system, and areas where cats tend to congregate were identified. Not surprisingly, certain areas of sane dunes are being used as industrial-sized litterboxes by the cats.

This type of information can be used in several ways. It can be useful for evaluating cat populations: where they are, where they go, and what happens to them over time. It can help identify areas where the cat population needs to be addressed through measures such as trap, neuter and release programs (as are being used in Miami Beach). It can also help with development of targeted education programs, by putting up warnings in heavily cat- and cat poop-infested areas. City health officials think that the combination of tracking, the increased spay/neuter program and targeted warnings to sunbathers have helped staunch the outbreak.

Image source:

Dogs and Giardia types

While the potential health risks to people exposed to dogs with Giardia have received a lot of attention (and concern), there's more and more evidence indicating that dogs pose a very limited risk to people. Giardia is a protozoal parasite that can cause diarrhea in numerous animal species, including people and dogs. It can also be found in healthy individuals, with several reports describing evidence of Giardia in the feces of approximately 7% of healthy dogs.

In the recent past, as easier-to-perform tests for Giardia became available, people sometimes tested healthy animals for the parasite, and then had to figure out what to do with positive but healthy pets. It has not been unusual for such dogs to be treated because of concerns about the potential for infecting people. However, it's becoming increasing clear that this risk is minimal.

The reason the risk is so low is due to the fact that not all Giardia are created alike. There are different assemblages (types) of Giardia, and not all types can infect all species. Knowing the types found in dogs and the types that cause illness in people can tell a lot about the potential human health risk. One more recent study has indicated that risk of animal-to-human transmission is likely very small.

In that study (Itoh et al, Veterinary Parasitology 2010), researchers tested fecal samples from 1794 puppies in pet stores in Japan. Giardia was detected in 23% of puppies. This is a pretty high number but it's not really surprising, as this highly mixed population of young, stressed animals would be considered high-risk compared to the average pet dog. All Giardia were assemblages C or D, which are dog-specific. Therefore, despite 23% of the puppies shedding Giardia, none posed a risk for human infection.

Yes, Giardia is a zoonotic infection, but the risk of dogs infecting people appears to be very low because dogs so rarely carry the types able to infect people. Beyond that, this is a "don't eat poop" disease, whereby the use of good hygiene practices to prevent inadvertent ingestion of Giardia from dog feces can reduce the risks even further.

Infectious disease considerations for fostering pets

Humane societies and shelters are often overwhelmed by the number of animals that come in. It's pretty uncommon to see much (if any) empty space in most shelters, and overcapacity shelters lead to increased risk of disease transmission, outbreaks and suboptimal care of the animals that are there.

One way of helping deal with overcrowding is fostering animals to people's homes for periods of time. Typically, foster homes take animals when shelters are at capacity, or take specific animals such as nursing cats, which are more difficult to care for properly in a shelter.

Most places have protocols for fostering, but they're not always very comprehensive and they don't always adequately cover some important areas. If you are thinking about fostering shelter animals, you need to think about the risks and whether you can manage them.

Are there people in the household that are at increased risk of infection?

Fostered animals should be assumed to be at higher risk of carrying and transmitting various infectious diseases. They can have high rates of carriage of various intestinal bacteria and parasites, along with a host of other microorganisms (e.g. ringworm). They may also be more likely to bite and scratch, not necessarily because they are aggressive, but often because they are young animals that may do so when playing. They may also be more likely to poop in the house.

Households with children under the age of 5, elderly individuals, pregnant women or people whose immune systems are compromised are at increased risk of various infections, both in terms of the likelihood of becoming infected and the likelihood of developing more severe disease. Households with these types of individuals should not foster animals. They are much better off having their own lower-risk pets.

Are there any "resident" pets in the household?

You might expect that someone willing to foster animals would also have their own pets, but that's not always the case. Non-pet owners are actually ideal, since this negates any risk of diseases being spread from or to household pets that live there long-term. However, it's more typical that foster homes also have such resident pets.

Are there any pets in the household that are at higher risk for infection?

As with people, there are some animals that are at increased risk of infection. These include the very young, very old, pregnant and pets with compromised immune systems. The latter group would include pets with chronic illnesses, those being treated with high doses of steroids for various diseases, animals with cancer, animals with diabetes, and a range of other issues. People owning a pet that fits into one of these categories should not foster animals because of the risk to their own pet. 

How do you reduce the risks associated with fostering animals?

  • May sure there are no high risk people or pets in the household.
  • Make sure the shelter or organization knows what they are doing. Make sure they have a clear protocol that says who will be fostered and how it's done.
  • Look at the animal before you get it. Visit it at the shelter. See if it looks healthy. If you have any questions, make sure it's examined by a vet before it reaches your home.
  • Use good hygiene. Wash your hands regularly. Properly clean up feces and clean litterboxes regularly.

If you have pets of your own:

  • Make sure they are vaccinated and on an appropriate parasite control program.
  • Keep the new animal away from your pet at the start. That lets you find out more about the animal, and it gives you more time to see if there are potential infectious disease concerns.
  • Do a controlled introduction of the new animal. Slow, supervised introduction of the animals can reduce the risk of bites or scratches.

Fostering is a good way to reduce pressures on humane societies and shelters, and to provide better care for some animals, like pregnant animals or those with young kittens/puppies. A good fostering program can be set up with limited risk to all involved, but infectious disease risks can never be completely eliminated. By accepting a new animal into your house, you increase the risk of exposing yourself and anyone else (human or animal) to infectious diseases. That's just a fact of life.

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California Vet Association park safety tips

The California Veterinary Medical Association has published recommendations for dog park safety. The document, entitled "Dog parks harbor risks as well as fun" emphasizes the benefits of park visitation but points out some risks and recommended precautions. Some of the risks associated with park visits include bites, scratches, and exposure to various infectious diseases.

Some basic and practical precautions that are recommended include:

  • Ensure your dog's vaccination status is current.
  • Make sure your dog is socialized and behaves well around people and other animals.
  • Monitor your dog closely.
  • Avoid mixing small dogs and big dogs.
  • Bring water for your dog to drink.
  • Clean your dog's paws when you leave the park (I'm not sure that one's very useful).
  • Have your veterinarian check your dog regularly for parasites (and other infectious diseases or risk factors).
  • Talk to your veterinarian about any (other) precautions you should take.

Overall, the document provides some useful and very practical information. A few things I would add:

  • Keep your pet away from the park when it's sick.
  • Make sure you promptly pick up dog poop and dispose of it properly.
  • If it's an off-leash park, spend a few minutes watching the other dogs that are there before deciding whether to let your dog off its own leash.
  • Make sure your veterinarian knows that your dog goes to the park if it becomes sick. There are some diseases that are more likely in dogs that visit parks, and outbreaks can also be associated with parks.  Knowing that your dog has access to a dog park might be an important part of the diagnostic process. As well, knowing that you visit the park regularly might change your veterinarian's recommendations for vaccination and deworming.

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Giardia in London (UK) shelter

A recent paper in the journal Veterinary Parasitology (Upjohn et al 2010) described a study looking at Giardia infections in dogs in a central London shelter. The researchers collected a fecal samples from dogs within 1 day of arrival and tested them for Giardia.

  • 21% of dogs were shedding Giardia on arrival at the shelter.
  • Shedding rates were higher in younger dogs.
  • Of the samples that were genotyped, almost all were Assemblages (types) C and D, the dog-specific types that are not thought to be able to cause disease in people.

This is one more study highlighting a couple of important facts about the protozoal parasite Giardia:

  • Giardia is common and can be found in healthy and diarrheic dogs. Studies of healthy pet populations typically reported lower rates than the 21% found here, but it is not uncommon to find Giardia in approximately 7% of healthy pet dogs.
  • Young dogs are more likely to be infected. That's also true for various other intestinal microorganisms that can cause disease. 
  • The majority of dogs that are shedding Giardia are infected with types that do not infect people. This is an important point and it needs to be considered when people are worried about infections from dogs (or trying to blame pets for human infections). There is limited risk of transmission of Giardia from pets to people. That doesn't, however, mean no risk. Since a small percentage of dogs can shed Giardia types that can infect people, common sense should be used when handling dog feces. Even if a zoonotic strain of Giardia is present in a dog's stool, it has to make it to someone's mouth to have a chance of causing an infection. Proper handling of feces and basic hygiene practices (especially hand hygiene) should greatly reduce the already low risks.

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Toddler risks losing eye to dog parasite...maybe

A few UK news outlets published a story the other day about a toddler with a severe eye infection that was attributed to Toxocara canis, the canine roundworm. Some parts of it didn't make a lot of sense so I held off commenting, but the story's spreading more widely now so I might as well raise a few issues.

The story is about a toddler that fell into a pile of dog feces while playing at the park, then wiped her eye. Her mother took her right home and washed the eye out. Then, according to the BBC:

"She woke up in the early hours screaming and her eye was bright purple and red and swollen shut with the eyelashes inside. She had a temperature and was very lethargic and in a lot of pain." Hospital tests confirmed toxocariasis, which resulted in Amiee contracting optical lobe cellulosis, which can lead to blindness and death if not treated within 72 hours.

Here's where I start to get confused. Eye infections are one problem cause by Toxocara canis. However, the disease (ocular larva migrans) develops when someone ingests infectious T. canis larvae from feces. It takes a few days to a few weeks after being passed in feces before the larvae become infective, so this would have to have been a pile of old feces (something that's certainly possible).

Nonetheless, as I said, ocular larva migrans develops when someone ingests the larvae, which then migrate out of the intestinal tract, journey through the body and end up in the eye. This doesn't happen in a few hours, as is described here. It takes much longer. Even if infective T. canis larvae were injected in the eye, you wouldn't see the type of severe inflammation around the eye that is shown in the picture on the BBC website. Fever is also rarely present with ocular larva migrans. The parasite gradually causes inflammation within the eye, not around it.

The girl is being treated with 3 antibiotics and an eye ointment. Again, this makes no sense for toxocariasis, since it's a parasitic infection within the eye. Antibiotics aren't going to be useful.

The rapidity of onset, the involvement of tissues around the eye, the presence of a fever and the reported treatment suggest to me that this is actually a bacterial infection of the eye and surrounding tissues, something that certainly could be related to the multitude of bacteria present in dog feces.

Regardless of the cause, the notion that dog owners need to be responsible and clean up after their dogs remains. Let's hope the physicians know what's going on and are treating Amiee properly.

Russian poop patrols

Apparently, Moscow parks are somewhat hazardous, at last in terms of where you step. Moscow dog owners have historically done a poor job of picking up after their dogs, and local officials are trying to intervene. Soon, all Moscow parks will have paper bags and plastic scoops for people to use to pick up after their dogs.

One dog owner, supportive of the plan, stated “It's absolutely essential – we really needed these bags. First of all, it's very convenient. But also, now I’m not worried anymore about leaving the poo just lying around. The park is so beautiful.” [I would have thought that if you were worried about leaving poo lying around, you'd just take the initiative to pick it up, but I guess a little boost is needed to get some people started.]

This initiative in being undertaken for two main reasons. One is the obvious unsightly nature of poop piles in parks. The other is concern about infectious diseases. Prime Time Russia states that bacteria in dog feces can cause "allergies and an infection that leads to blindness. When dog feces dries and turns to dust, these bacteria are spread. Last year, 400 people in Moscow were diagnosed with the infection. The worst is the fact that since the dust is lying on the ground, children are particularly exposed to the danger."

This is a bit confusing. Feces isn't much of a concern in terms of allergies. Further, I'm not aware of common bacterial infections from dogs that can cause blindness in people. I suspect they actually mean ocular larva migrans, a parasitic disease that can occur when a person inadvertently ingests eggs of the canine roundworm (Toxocara canis) that have been passed in feces of a dog, and that have lived in the environment for a long enough time to mature to their infective state. Regardless, there are clearly infectious disease concerns from exposure to dog feces in parks, particularly to children.

The approach of providing supplies for people to clean up after their dogs is novel. Some people might find it strange, since in many regions, people are quite good about picking up after their dogs. Providing supplies to people in those regions probably wouldn't have much of an impact, since the responsible owners bring their own and the rest probably wouldn't use them anyway. This type of initiative is potentially quite useful in areas where cleaning up after your dog is not as ingrained, and where providing supplies can act as both a reminder and as a way to assist. It will be interesting to see what kind of impact this has.

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Baylisascaris and dogs

Recently, I was speaking with a physician who mentioned that a colleague has recommended that people with raccoons in their yard get rid of their dogs because of the risk of Baylisascaris procyonis. This parasite, also known as the raccoon roundworm, can cause severe neurological disease in people that ingest infective parasite eggs from the environment.

The most severe type of disease caused by the migrating larvae of this roundworm (neural larval migrans) is very nasty, and usually causes death or serious, severe neurological deficits.  However,  the recommendation to get rid of dogs when there are raccoons around makes no sense. Here's why:

  • The main host for Baylisascaris is the raccoon. A large percentage of healthy raccoons (over 90% in some areas) are infected and pass large numbers of parasite eggs in their stool.  Exposure to eggs from raccoon feces is the main source of human infection.
  • Human infections are very rare. They predominantly occur in people that are at increased risk of ingesting feces or dirt, based on their age or behaviour.
  • Dogs can be infected with Baylisascaris, but this is rare.
  • The small number of dogs that are shedding Baylisascaris in their feces do not pose an immediate risk to people. Eggs that are passed in feces are not immediately infective. Eggs must mature in the environment (which usually  takes 2-4 weeks) before they are able to cause infections.
  • There are no clearly documented cases of dogs being a source of human infection.
  • The main risk from dogs is probably the potential for dogs to carry old (i.e. infectious) Baylisascaris eggs into houses on their haircoats, after roaming around raccoon infested areas.

How do you reduce the already very low risk associated with Baylisascaris and dogs?

  • Discourage raccoons from living near your house. Raccoons defecate in certain areas or "latrines," where the soil becomes heavily contaminated with raccoon feces, and where tremendous numbers of infectious eggs can be present.  If you make your yard uninviting to raccoons, then they won't establish a latrine near your house.
  • Carefully clean any raccoon latrines that might be on your property.
  • Don't let you dog have contact with raccoon latrines.
  • If your dog has had contact with a raccoon latrine, give it a bath. Baylisascaris eggs are sticky and can stick to the dog's coat quite well, so a thorough bath is much better than a quick rinse or brush. Wear gloves and some form of protective outwear (e.g. a coat that you take off after and promptly launder) while bathing the dog. Wash your hands thoroughly when done.
  • Closely supervise people at increased risk of ingesting feces or dirt (e.g. young children) when they're outside.
  • A routine deworming program will eliminate Baylisascaris in the intestinal tract of a pet dog, in the unlikely event it's been infected.
  • Prophylactic treatment of dogs that have eaten (or have a tendency to eat) raccoon feces could be considered, but the need and usefulness of this is not clear.

Bottom line: You don't need to get rid of your dog if there are raccoons in your yard.  The risk of Baylisascaris infection from your dog is extremely low, and the steps above can help you decrease the risk even further.  Getting rid of the raccoons (instead of the dog) will be much more effective.

More information about Baylisascaris and neural larval migrans is available in our archives.

Cryptosporidiosis from wildlife centre lambs

The May 2010 edition of Emerging Infectious Diseases contains a report about an outbreak of cryptosporidiosis in Scotland (McGuigan et al. 2010). Cryptosporidiosis is a common parasitic disease caused by Cryptosporidium, a protozoal parasite. It causes diarrhea, which is usually annoying (to say the least) but self-limiting in healthy people, but the infection is potentially fatal in people with compromised immune systems.

An investigation was launched after a single case of cyrptosporidiosis was diagnosed by a Scottish laboratory. The reason a single infection caused such concern is that it was suspected to have originated from contact with lambs at a wildlife centre, so there was potential for exposure of many people. The concerns were valid, since a total of 128 cases of cryptosporidosis were uncovered during their investigation, and 117 of the people affected had visited the wildlife centre. Another 252 unconfirmed cases were also identified.

The investigation suggested that direct contact with diarrheic lambs was the source of infection. Lambs (and calves) are high risk for shedding Cryptosporidium, even when they're healthy.  Diarrhea increase the risk of transmission from these animals even more, because diarrheic animals are more likely to (1) shed the parasite and (2) have fecal staining of their haircoats, which increases the likelihood of fecal contact for every person and animal around them. That's why young ruminants (e.g. lambs, calves) as well as young poultry are considered inappropriate for petting zoos and other similar public animal contact events. This outbreak is yet another example of why these recommendations are in place.

At the wildlife centre in this study, children were apparently encouraged to pick up the lambs, despite visible diarrhea. No handwashing facilities were near the lamb petting area and it took "considerable effort" to find a location to wash your hands anywhere on site. Alcohol hand sanitizers were available, however Cryptosporidium is resistant to alcohol. Handwashing is a critical component of disease prevention, but unfortunately it is very underused. In general, people are becoming much more aware of the need for handwashing, but even so, if handwashing facilities are not conveniently located, people tend not to go to much effort to find them. That leads to increased risk of infections, as was the case here.

Control measures at the wildlife centre implemented after the investigation included removal of the lambs (who should never have been there anyway), disinfection of the premises with bleach (although disinfecting a farm environment is very difficult, and Cryptosporidium is also resistant to bleach), and stopping direct contact between animals and visitors.

As we enter the season when there are more fairs, petting zoos and other animal contact events, facility managers need to pay attention to important factors like:

  • Readily available hand hygiene facilities
  • Good design to control the types of human-animal contact and to steer people towards hand hygiene stations
  • Appropriate animals: no calves, lambs or chicks
  • Proper supervision of people and animals

A little common sense goes a long way. The goal is to set up these events so that there is still a beneficial impact of seeing and interacting with animals while reducing (but never eliminating) the risk of disease transmission. A 100% safe petting zoo is not achievable (there's always some risk in life), but some pretty simple measures can greatly reduce the risks while still providing excellent entertainment and educational opportunities.

Ascaris lumbricoides and dogs

Roundworms (ascarids) are common parasites of many animal species. In dogs and cats, Toxocara canis and Toxocara cati are the main problems. In people, it's Ascaris lumbricoides, which is often called the "human roundworm." It's a very common parasite that is thought to infect about 25% of the world's population. Rates are highest in tropical, developing areas with poor sanitation, poor hygiene, and (as one author stated) a tendency for "promiscuous defecation." Basically, the more human feces in the environment and the lower the degree of hygiene, the greater the risk of inadvertently ingesting parasite eggs.

Traditionally, it's be thought that this parasite is specific to people, but occasionally, A. lumbricoides eggs have been found in the feces of dogs. The general assumption in these cases has been that the dogs just ingested eggs from the environment, and the eggs simply passed through the dog's intestinal tract and out the other end. However, a recent paper has challenged that thought. The study (Shalaby et al. Parasitology Research, 2010) found adult A. lumbricoides worms in the small intestine of 8% of tested dogs in Egypt. The presence of adult worms means that the dogs ingested the eggs and that the eggs were able to develop to adults in the dog's intestinal tract. The adult worms were producing eggs, suggesting that dogs could be a reservoir for A. lumbricoides, beyond just spreading around eggs that they ingested from human feces.

Overall, dogs probably play a minimal role in human infection with this parasite, but it's an additional dynamic to consider. However, the best approach to reducing the risks associated with dogs and A. lumbricoides probably don't have anything to do with dogs - rather, the keys are reducing environmental contamination with human feces and improving general hygiene practices.

Image: Adult female A. lumbricoides. (source: CDC Division of Parasitic Diseases (DPDx))

Deworming dogs... How often?

Deworming has become a controversial subject. There are numerous opposing views, strong opinions and conflicts of interest that drive a lot of debate on the subject. There's no argument that parasites can be bad for pets and some can pose a risk to people. There's no argument that we want to reduce parasite burdens in pets to improve pet health and decrease human risks. It's the "how" that causes all of the problems. Developing deworming strategies requires consideration of a several different things, including:

  • What parasites are in the area?
  • Are the risks the same all year round or are they seasonal?
  • What parasites pose a risk to an individual pet or what are the pet's chances of exposure? (e.g. Does the pet go outside? Is it exposed to many other animals? Are there multiple pets in the household?)
  • Are there any people in the household at particular risk for parasitic infections? (e.g. young children, people with developmental disorders that might be more likely to be exposed to pet feces?)

Everyone agrees puppies and kittens need more aggressive deworming, but there are a few different approaches to managing deworming in adult animals.

The Companion Animal Parasite Council advocates monthly deworming for a few reasons. One is that, based on the duration of activity of the drugs used, monthly treatment prevents establishment of significant parasite populations in the animal (and therefore also in the animal's environment). It also keeps the treatment user-friendly - it makes it easier for people to remember to treat their pet. Some concerns with this approach include its "one plan fits all" mentality, despite the fact that there are great differences in the risks between different regions, and even between pets in the same area. There are also concerns about such heavy use contributing to the development of parasite drug resistance (which is a problem in some other species like horses and sheep), although this doesn't seem to be a major concern... at least not yet.

Recent European guidelines take a somewhat different approach and use a philosophy more geared towards individual risks for each animal. These guidelines recommend that if regular deworming is used, animals should be treated at least 4 times a year, with no more than 3 months between each treatment. This is based on some research indicating that dropping treatment to 3-4 times per year had no effect on parasite levels. This approach is therefore more conservative (in terms of the number of treatments) and probably has less of an impact on the development of resistance, but it requires more organization and thought. If used properly, it's probably a good approach.

Yet another approach was recommended by a Canadian Parasite Expert Panel. With their approach, in low-risk households (both pets at low risk for parasite exposure and people at low risk of infection), treatment is based on fecal examination results or, if fecal testing is not performed, once or twice yearly treatment is recommended. In high risk households, fecal testing is recommended 3-4 times per year, with treatment based on results, or administration of routine preventive treatment at least 2, and preferably 3-4 times per year. The main criticism of this approach is that it's more complicated and perhaps prone to errors or missed treatments.

There's no clear answer, nor should there be. There really can't be a "one program fits all" approach that properly addresses the risks for all pets (and people) in all regions. Tailoring the deworming strategy to your pet, based on your pet's and your family's risk, is the logical approach. Regardless of the chosen approach, regular fecal testing is a good (and underused) way to assess what's going on with parasites in your pet, and to identify treatment failure or the emergence of drug resistance.

Monthly heartworm prevention has an impact on what you do as well, since typical heartworm preventives are also effective against roundworms and hookworms, the main parasites targeted by routine deworming. If you are in a region where heartworm is present, monthly treatment during the heartworm season is indicated, and the main decision that needs to be made is what to do the rest of the year (where heartworm isn't a risk year-round).

Composting pet waste

An article in Saturday's Toronto Star discussed composting options for people without organic waste pickup or the ability to have a backyard composter, including indoor composters that can be used by apartment or condo dwellers who want to satisfy their eco-friendly side.

They mentioned that one of the composters they highlighted (NatureMill) can apparently handle pet waste, but composting animal feces is not a good idea. Pet waste (feces +/- cat litter etc.) can contain a wide range of potentially harmful parasites and bacteria. The composting process can generate enough heat to kill these bugs, but it's not guaranteed to do so, and I'd be especially concerned about small indoor composters. Having a few nasty things in the composter itself isn't necessarily a big deal, but what happens down the line? People can be exposed to these microorganisms when removing compost, and (maybe more importantly) compost usually ends up in gardens where the bad bugs can contaminate the soil, as well as anything grown in the garden.

One concerning microbe is the protozoal parasite Toxoplasma gondii. Cats are the natural reservoir of Toxoplasma and can pass it in their feces (usually only for a short period), but most people that become infected by Toxoplasma are likely exposed to the oocysts ("eggs") outside in gardens, or from contact with contaminated foods (e.g. unwashed vegetables). (Undercooked meat can also be a source of infection, but that's another story).  Composting may not kill this parasite, so when pet-waste compost is put into flower gardens or vegetable gardens in which people work, the risk of exposure to Toxoplasma may be increased. The risk of transmission from an individual cat is admittedly low, since only a very small percentage of cats are shedding the parasite at any one time (even though most have at one point), but it's a preventable risk. There are also various other microorganisms that are potential concerns. While composting is a great way to dispose of most organic wastes, it's best to keep putting dog and cat feces in the garbage or down the toilet (and wash your hands afterward, of course).

If you really feel the need to compost pet waste, the safest alternative is probably to have a separate composter for pet waste that you handle a bit differently: pay careful attention to hand hygiene after handling the compost, and make sure the compost isn't used in gardens or other areas where people might have contact with the soil.

Click image for source.

Heartworm in people

Heartworm is an important problem in dogs. It's a parasitic disease caused by Dirofilaria immitis and is spread by mosquitoes. It can cause serious, even fatal disease, and routine testing and preventive medication is an important thing for dogs in areas where D. immitis is present. Dogs (wild and domestic) are the natural host for this parasite, but other species can be accidentally infected, including people and cats. People become infected by being bitten by a mosquito that is carrying the parasite, having acquired it from an infected dog. Human infections seem to be quite uncommon and, interestingly, while this is a serious problem in dogs, it tends to be rather innocuous in people. In fact, the biggest problem with heartworm infection in people is the fact that it can be confused with other, more serious problems, leading to invasive testing.

After infecting someone, D. immitis works its way to the blood vessels in the lungs. This can result in  a small area of inflamed tissue in the area. If a chest x-ray is taken, a "coin lesion" (a small, usually 1-3 cm spot) is often present. The parasite infection usually doesn't cause any problems in people, but lung cancer and tuberculosis can look the same on x-rays. Usually, open-chest surgery ends up being performed to get a biopsy of the area because of the concerns about cancer. In heartworm cases,the biopsy identifies the problem as D. immitis, which is much better than cancer, but the risks associated with having undergone such an invasive procedure are much greater than that of the parasitic infection itself.  

Typically, treatment is not recommended in people because the infection rarely causes problems and people are "dead end" hosts, meaning they cannot pass on the infection. (Unlike in dogs, infected people don't have the parasite microfilaria in their blood, which is how the infection is passed on to  mosquitoes and other animals).

Heartworm is a rare and rather innocuous problem in humans - it's nothing to lose sleep about.

Image: A diagram of a very severe case of heartworm in a dog, in which there are so many worms in the pulmonary arteries that there is "back-up" of the parasites into the right side of the heart, which is how the parasite got its common name.

Ear mites and the strange pursuit of knowledge

Ear mites are a common problem in dogs and cats, particularly in young animals, as well as in strays and animals in shelters. The species of mite typically involved is called Otodectes cynotis. It is transmitted between individuals by direct contact (basically hopping animal to animal, as it does not survive for long in the environment), and causes an extremely itchy ear infection (which can get even worse if there is secondary infection with bacteria or fungi).

There are a few reports of suspected infections with Otodectes in people. Considering how common ear mites are in cats and the small number of reported human infections, transmission between pets and people is probably rare, but it certainly can occur. Most of the reports are somewhat circumstantial, involving people with itchy skin lesions that developed after a pet was diagnosed with ear mites. However, one curious veterinarian took it a step further. 

Dr. Robert Lopez, of Westport, New York, intentionally infested himself with ear mites from infected animals, and described the outcome in a 1993 edition of the Journal of the American Veterinary Medical Association. First, he took a sample from the ear of a cat with ear mites and placed it in his own ear. He described the scratching sounds and movement that he could feel as the mites explored his ear canal. Severe itching developed, to the point where "sleep was impossible." The intensity of the itching and mite movement decreased over time and the infection resolved by itself within a month.

Personally, I think I would have stopped there. (Actually, I wouldn't have made it to that point, but if I did, I certainly wouldn't have tried it again.) Yet, Dr. Lopez wanted to confirm his findings so, a few weeks later, he infected himself again with mites from another cat. The same type of disease developed, although it was less severe and only lasted two weeks.

Guess what he did next - he tried again, wanting to see if the reduction in severity might indicate development of immunity. So, he infected himself a third time, with the outcome being milder disease. This suggested to him (logically so) that immunity to the mites might develop, something that fits with the fact that ear mite infestations are more common in young animals.

Self-experimentation is generally frowned upon, but has been the source of remarkably scientific discoveries, even Nobel Prize winning discoveries (e.g. the role of Helicobacter pylori in gastric ulcers in people). I don't think Dr. Lopez is in line for any prizes, but it shows how a little academic curiosity along with minimal squeamishness can provide some interesting information.

What's the relevance of all this? If your pet has signs of ear mite infestation (e.g. scratching at the ears, dirty material inside the ears), get it examined and treated. If nothing else, this needs to be done because it's a very uncomfortable problem for the pet. There's also some risk of human infection, but it's probably minimal. The mites have to make it from the pet's ear to your body to cause problems. The quicker they are treated, the lower the likelihood of this occurring. Human ear mite infestations, be they in the ear or on the skin, seem to resolve by themselves, with treatment of the animal being the most important part of control. However, it can be a pretty uncomfortable condition and one most people (with the possible exception of Dr. Lopez) would certainly rather avoid.

Giardia outbreak closes shelter

A Fort McMurray (Alberta) SPCA shelter has been closed because of a Giardia outbreak. Giardia is an intestinal parasite that can cause diarrhea in dogs (and other species, including people) but can also be found in about 7% of healthy dogs. Giardia infection was confirmed in four dogs in the shelter, which led to the rather aggressive measure of closing the shelter. Shelter personnel suspect that the infection started with one dog, who spread the parasite to some other dogs that were in close contact with it. Giardia is passed in stool and animals get infected by ingesting Giardia oocysts from stool contamination in their environment or water sources.
Shelter personnel speculated that "If [the first dog to be infected] went for a walk with the snow melting, of course there's lots of little presents underneath the snow, so when she goes for a walk and she steps in, say another dog's feces, and then licks her paws, she can get it."
It's pretty unlikely that old feces revealed by thawing snow were the cause, since freezing is a pretty effective way to kill Giardia. More likely, the parasite was brought into the shelter by a healthy dog, considering that a reasonable percentage of dogs are shedding Giardia at any time. Why it spread to other dogs is a different question, as is whether the other animals were sick (with diarrhea) and whether Giardia was really the cause if they were. As with any organism that can be found in healthy animals, it's hard to say for sure whether Giardia actually caused any disease or whether there was some other cause that wasn't detected and the affected dogs just happened to be shedding Giardia at the same time.

Giardia usually causes pretty mild disease that gets better on its own or with treatment. Shelter personnel stated "We are in desperate need for help from the public as far as raising funds for medical, because obviously it costs a lot of money to treat the dogs. It's a lot of money to treat an animal with giardia." It's actually pretty cheap to treat individual cases, but this makes me wonder whether they are treating all dogs in the shelter. That's not something I'd recommend because there's little evidence that treatment of non-diarrheic animals is needed or useful. 

Presumably this outbreak (whether it was caused by Giardia or something else) will end soon, either because of or despite of what was done. You never know if you did something to control the outbreak or whether it just ran its natural course. If it truly was Giardia, I'd be surprised if there are more problems, but resolution of the outbreak won't change the fact that many dogs that they bring in will be shedding the organism.

Giardia is a cause of diarrhea in people, but we now know that dogs probably play only a minor role in human disease. The type of Giardia that is most often found in dogs is a dog-specific type (Assemblage D) that cannot infect people. Unless these dogs were infected with a strain that can infect people (uncommon but not impossible), there's no risk to people. Regardless, avoiding contact with stool, especially diarrhea, is still a good idea - for prevention of Giardia and other diseases.

Baylisascaris in Winnipeg

There was another paper published in the August issue of the Canadian Veterinary Journal about Baylisascaris procyonis (roundworms) in raccoons, this time in Winnipeg, Manitoba (Sexsmith et al 2009). The study was actually undertaken after infection with B. procyonis larvae was identifed as the cause of death of several animals in the collection at the Assiniboine Park Zoo in Winnipeg.

The researchers collected feces from 52 active raccoon latrines around the city and from 114 "nuisance" raccoons that were caught, euthanised and submitted for necropsy to the local lab. Interestingly, the vast majority of latrines and nuissance raccoons were found close to the two major rivers that run through Winnipeg. Half (50%) of all the latrines were positive for roundworm eggs on at least one sample (out of a possible 3). Among the necropsied raccoons, 61/114 (53.5%) were positive for roundworms. Adult raccoons were almost four times as likely to carry roundworms than juveniles (which is in contrast to a previous study that found juveniles more likely to be infected), and bigger raccoons (over 2.75 kg) were more than seven times as likely to carry roundworms compared to smaller animals. Although there are regions where the prevalence of B. procyonis s reported to be very low, Winnipeg, like many other regions of North America, has joined the ranks of those where the prevalence is high and the public needs to be aware of the associated risks.

The most severe zoonotic disease caused by B. procyonis is called neural larval migrans (NLM), which results from migration of parasite larvae through the central nervous system (i.e. brain). Two of the reasons this is much more of a concern with raccoon roundworms (Baylisascaris) compared to dog and cat roundworms (Toxocara) are:

1) A massive number of parasite eggs are passed in the feces of infected raccoons (which typically have a very high burden of adult worms). Coupled with the fact that the eggs are further concentrated in areas where many raccoons defecate (latrines), this can lead to heavy exposure of people (or animals) who come in contact with the soil in these areas, which greatly increases the risk of infection.

2) The larvae of B. procyonis are very active migrators, and they get bigger as they migrate through tissues - much bigger than Toxocara larvae ever get, which means they also tend to cause a lot more damage before they're finally (if ever) trapped or killed by the body's immune response.

Natural infection of dogs living in the same areas as raccoons has been found - it's not common, but it appears to occur frequently enough to warrant noting. Dogs and cats can also be infected by their own species of roundworms, which will also result in parasite eggs being shed in the feces. It's important to have your veterinarian perform a fecal examination for your pet on a regular basis so any parasite infestations (roundworm or other) can be treated.

Dogs and cats may also be susceptible to larval migrans in the same manner as people (and the animals at the zoo in Winnipeg) if they are exposed to high numbers of infectious eggs. Remember that roundworm eggs must be swallowed in order for infection of any kind to occur, so good hand hygiene and avoiding soil contamination of food are key to preventing transmission. Also, do not allow your pet to dig or play in an area where raccoons defecate (preventing direct contact between your dog and raccoons should go without saying!).  And of course, feces of any kind (and from any species) should be treated as infectious material, and handled with appropriate precautions.

More information about Baylisascaris and raccoon latrines is available in our archives.

PInworms and pets

Pets as a source of pinworms in people (especially children) has been a widespread misconception. A recent article at gives a good overview of pinworms in people and has a nice section about pets.

"Pinworms that affect humans cannot infect animals or pets. However, some microscopic eggs may land on a pet's fur and then be transferred to human hands when stroking (petting). It is important to remember that the problem is not the pet, it is human hand washing and hygiene."

This nicely explains two key concepts:

  • People are the source of human pinworms.
  • Hand hygiene is an important routine practice around pets.

Bali rabies vaccination plan

A rabies epidemic has been underway in Bali for some time. There have been 25 deaths, with 2 occurring in the past 2 weeks. There are several reasons for this ongoing problem: large numbers of dogs (especially feral dogs) with limited vaccination, rabies circulating in the feral dog population, inadequate post-exposure treatment of people, and poor education of the public regarding the risks of rabies and how to properly address dog bites.

An encouraging sign is the institution of a mass rabies vaccination program for dogs. Unfortunately it won't start until February, which is disappointing because some people may get infected and die in the interim, but there are likely considerable logistical challenges to overcome, making some delay unavoidable.

The goal of this program is vaccination of 70% of all dogs in each affected regency. According to the recommendations of the World Health Organization (WHO), 70% is the proportion of the canine population that needs to be vaccinated in order to have a chance of eradicating of canine rabies from a given area. It's a challenging goal given the number of feral dogs and the limited resources available in Bali, but it's critical to vaccinate as many dogs as possible. It is estimated that there are approximately 500 000 dogs on the island. Approximately 137 000 dogs have already been vaccinated and another 39 000 have been culled (destroyed). Vaccination will not be performed in two regions because rabies cases have not been identified there. (Hopefully they have good enough surveillance to be very sure that rabies truly isn't in the dogs in those areas. It's a bit of a gamble otherwise.)

One thing that has not been specified is how they intend to handle vaccination of feral dogs. It's not clear whether the numbers mentioned here include feral dogs and whether efforts are being directed at pet dogs only or both pets and feral dogs. Poor compliance with booster vaccinations was cited as a concern, implying this was only focused on pets. Achieving 70% vaccination of the pet population is an important step, but if there is still uncontrolled circulation of rabies in the large pool of feral dogs, eradication will not be possible. Hopefully, trap-vaccinate-and-release programs or oral rabies bating will be used to address the feral dogs.

Image: Mt. Agung, southern Bali

Giardia in dog parks

There is a recent paper in Preventive Veterinary Medicine about a study of Giardia in canine stool samples collected from urban green areas around Pisa, Italy (Papini et al). The authors went to parks and similar areas and collected stool samples off the ground. They then tested the samples for the presence of Giardia and (very importantly) tested the Giardia to determine whether they were types that typically only infect dogs or whether they were types also found in people.

They found that 31% of stool samples contained Giardia. That's higher than in some recent North American reports. The number of Giardia cysts ranged from 2 to 1428 per gram of feces. Less than 1% of the Giardia were types that are of concern for transmission to people. Therefore, they concluded that parks pose a risk to dogs, since there is a good likelihood that dogs could be exposed to Giardia. However, the risk to people from Giardia found in these parks is minimal given the types that were found.

The risks to dogs and people can be decreased by the simple act of picking up poop.

More information about Giardia can be found on the Worms & Germs Resources page, and in our archives.

HIV/AIDS, kids and pets

The Centers for Disease Control and Prevention (CDC) has released updated Guidelines for the Prevention and Treatment of Opportunistic Infections Among HIV-exposed and HIV-infected Children. A small but still important part of this document involves recommendations for contact with animals. It's a nice, balanced document that acknowledges the risk but doesn't make unnecessarily restrictive recommendations.

Among the important recommendations regarding animals:

  • When getting a new pet, avoid dogs and cats less than 6 months of age or strays: These animals are at higher risk for shedding various infectious diseases and are more likely to have problems with biting and scratching.
  • Avoid contact with animals that have diarrhea.
  • Wash hands after handling pets.
  • Avoid contact with pet feces.
  • Avoid contact with reptiles, chicks and ducklings: These are very high risk for Salmonella.
  • Avoid contact with calves or lambs at farms or petting zoos: These animals are high risk for various infectious diseases such as Cryptosporidium and Salmonella.

These recommendations also largely apply to other high-risk groups, including people (of all ages) with compromised immune systems and young children (especially less than 5 years of age). A key point is normal contact with common household pest using basic hygiene practices is considered a low risk. Infection control isn't rocket science. It involves basic and practical measures that can reduce risks associated with animal contact.

Raccoon deterrents

We've written various posts about raccoons, raccoon latrines and concerns about the raccoon roundworm (Baylisascaris procyonis). I received a question today about how to keep raccoons from coming back after a latrine has been identified and cleaned. It's a good question, and one without a simple answer.  I've looked through various sources and have found a wide range of recommendations. (Whenever I see such a wide-ranging list of recommendations, I wonder whether anything actually works.)

Home remedies include:

  • Sprinkling pure soap flakes on the lawn and watering thoroughly
  • Mixing bone meal in garden soil
  • Sprinkling diluted tabasco sauce over fruits and vegetables (wash before eating, as you should anyway!)
  • Lighting up the area where raccoons are a problem

Various commercial deterrent compounds are available, such as one that apparently has the scent of a coyote, or one that's a combination of vinegar, pepper and sulfur.

Another approach is motion-sensitive deterrents. Motion-sensor-based lights can be useful since raccoons often come rooting around in the evening or overnight, and lights that turn on when they approach could be effective. These would require a power source, which could be limiting in some places like sheds. Similarly, motion-sensor based systems that spray water or citronella (sometimes used to keep cats out of certain areas or off countertops) could be useful. Battery-operated units could be used anywhere. (Here's a link to one. I've never used it but it shows you what I'm talking about). There are also motion sensors that hook up to hoses.

One problem with deterring raccoons is their intelligence. They can often find ways around deterrents, or adapt to them. Along with any attempts to actively deter the raccoons, it is also important to try to reduce the desire of the raccoon to come to the location. If there is a good food source or other desirable attraction, the raccoon will probably try harder to stay around. Tightly covering garbage cans and removing other possible food sources (e.g. food for outdoor cats) are important steps. Making sure neighbours (or other family members) aren't feeding the raccoons is also important, because food is a great motivator.

Raccoon latrines in Chicago

If you live in the suburbs of Chicago (or probably many other cities as well), chances are pretty good that you live close to a raccoon latrine. Raccoons like to defecate in specific areas (raccoon latrines) which can become highly contaminated with eggs of Baylisascaris procyonis, the raccoon roundworm. Human disease caused by this parasite is rare, but when it occurs, it can be devastating. Infected raccoons can shed around 20 000 Baylisacaris eggs per gram of feces (see image right), and the eggs can survive for long periods in the environment, so it's easy to see how biohazardous a raccoon latrine could be.

A study in the upcoming edition of Emerging Infectious Diseases (Page et al) looked at 119 backyards in the Chicago suburbs. Latrines were found in 51% of yards, with up to six latrines per yard! Baylisascaris eggs were found in samples collected from 23% of latrines. The likelihood of having a latrine in the yard was lower in houses farther away from forested areas. No other factors were identified as associated with the presence of a latrine, however there was a trend towards increased likelihood if a food source (e.g. bird feeder) was present.

The fact that raccoon latrines are so common and that a high percentage of raccoons shed Baylisascaris should raise concern, and emphasize the need for good hygiene. At the same time, the rarity of disease despite the widespread presence of infected raccoons should be remembered. You don't get infected by walking by a raccoon latrine, you get infected by ingesting (swallowing) the parasite. Avoiding this is simple, and as the folks at Barfblog (a food safety blog) would say, the key is: "Don't eat poop". Simple measures can reduce the risk, such as avoiding contact with raccoon feces and washing your hands after being in potentially contaminated areas. Young kids are at highest risk because they are more likely to put things in their mouths, so keeping children away from areas potentially contaminated by raccoon feces is important, along with good attention to hand hygiene.

Since raccoon latrines are an obvious source of infection and many (of the limited number of) human cases have been where latrines were close to childrens' play areas, eliminating latrines is also a good idea. Details on cleaning up latrines are available in an earlier Worms & Germs post.

More on Giardia in healthy dogs

New research provides more information on the debate about testing and treating of healthy dogs for Giardia. Two abstracts on the subject by researchers at Colorado State University were presented at the recent American College of Veterinary Internal Medicine conference.

In the first study (Clark et al), fecal samples were collected from 220 healthy dogs. Giardia was detected in 11.4% of samples, but no dogs carried assemblages (types) known to cause disease in people.

In the second study (Lappin et al), they evaluated whether treatment of healthy dogs that were shedding Giardia would eliminated the parasite. Sixteen infected dogs were treated with either fenbendazole or nitazoxanide. Eight (50%) of the dogs had to be removed from the study because of adverse effects from treatment! Of the dogs that completed the study, Giardia was still detected in 63% of dogs 34 days after treatment, indicating that the infection wasn't eliminated or that dogs were quickly re-infected.

These studies provide more support of the notion that there is no indication to test or treat healthy dogs for Giardia. Testing makes no sense when the parasite is so common but most infected dogs are healthy, and when strains carried by infected dogs are usually of no consequence to people. Giardia is essentially a normal part of the intestinal microflora in many healthy dogs. Treatment of healthy carriers isn't indicated because it can make dogs sick and because it doesn't work very well.  Remember: above all do no harm.

The bottom line is don't bother testing healthy dogs for Giardia or treating healthy dogs in normal households.

Giardia and high-risk households

Giardia is a relatively common protozoal parasite that can cause diarrhea in people and dogs (among other species). It can also be present in healthy pets, with most studies reporting Giardia shedding in approximately 7% of healthy dogs. While recent research indicates that a large percentage of dogs with Giardia carry types that do not infect people, this parasite is still a concern, particularly in households high-risk households with immunocompromised individuals, very young children and elderly persons.

What do I do if I'm in a high-risk household and my dog is diagnosed with Giardia?

  • Genotyping of Giardia from the dog to see if it is a strain that affects humans would be ideal, but this is not readily available outside research labs. Maybe in the future this will become a standard test.
  • The dog should be treated according to your veterinarian's instructions. The entire treatment course must be completed.
  • All other dogs and cats in the house should be treated at the same time, even if they have been tested and were negative, because we want to avoid "cycling" of Giardia between the pets.
  • All animals should be bathed on the first and last day of treatment to reduce the risk of re-infection from Giardia cysts on the fur. This should not be performed by high-risk individuals, and is probably best done at a veterinary clinic or groomer to reduce bathroom contamination, if bathing can't be done outside.
  • All animals should be tested after treatment to ensure the infection has been eliminated. This is usually done about 5 days after the last treatment. If antigen testing is used, some animals will still have positive results 5 days after treatment because of dead Giardia still working their way out, in which case re-testing at around day 21 post-tretament is recommended.
  • Care should be taken to avoid direct and indirect contact with feces. Close attention to handwashing promptly after cleaning up feces or fecal-contaminated areas is very important. Regular handwashing after contact with pets is always important.

Traveling parasite roadshow

There have been a few press articles lately about the Companion Animal Parasite Council (CAPC)'s traveling roadshow on parasitic zoonoses. Measures to increase awareness about zoonotic diseases and encourage appropriate preventive measures are needed, and traveling shows such as this have the potential to reach wide audiences. However, it's important for people to critically assess everything they are told and understand the sources. CAPC produces some excellent educational material but, to my knowledge, it is fully funded by the pharmaceutical industry. That doesn't necessarily mean that CAPC's educational efforts are suspect - people participating with their roadshow have solid credentials, but you do have to critique some of the things CAPC says.

One news article about CAPC's efforts states that "The CDC reports that about 14 percent of the total U.S. population is currently infected with Toxocara, or internal roundworms, contracted from dogs and cats." I don't think that's accurate information. I believe that this is based on seroprevalence data, meaning 14 percent of the population has antibodies against Toxocara. The presence of antibodies means that at some point in life the person's (or animal's) body was exposed to Toxocara and produced antibodies.  It does not mean that these people were ever sick and it certainly does not mean that these people are currently infected. Toxocara can cause serious infections and is a concern in some regions (although it's extremely rare in Ontario), so it warrants some attention, but we need to take a balanced and evidence-based approach.

One common theme in all of the reports that I've read lately is the statement that "The CAPC recommends that pet owners use preventive medicine year-round to control internal and external parasites for the life of their cat or dog, no matter where they live."  There's simply no evidence supporting this broad of a statement. Risks in warm southern climates are not the same as in northern areas with cold winters. Prevalence rates of different parasites vary greatly between regions. There is no evidence supporting year-round deworming of dogs and cats in all regions. Statements like this weaken the other good educational information CAPC has, particularly when you consider their funding source.

Don't disregard educational materials from CAPC or other industry-sponsored groups, just don't accept them as gospel. Critically assess the information, and don't be afraid to ask for facts, or to get information from other sources.

For more information about deworming recommendations for dogs and cats in Canada, see this previous Worms & Germs post.

Baylisascaris (raccoon roundworm) in cats

A reader posed this question, with respect to having raccoons living around the house:

"One thing that causes me concern with the raccoon roundworm is the possible danger of infection to my pets and myself through the feces left behind from the raccoons in the yard and possibly in my vegetable garden. Can I acquire the roundworm from working in the soil and/or from my root vegetables etc? My cats mingle near the raccoons, they don't bother each other, should I get my cats tested?"

Certainly, working outside (particularly in soil) leads to the potential for exposure to many disease-causing agents, including Baylisascaris, as well as dog and cat roundworms (Toxocara spp.). Eating unwashed/uncooked vegetables is also a risk. However, in the grand scheme of things, the risks to the average person (not very young or very old, functional imune system) are minimal, especially if basic hygiene measures are used, such as washing hands after working in the garden, and thoroughly washing vegetables. Raccoons tend to defecate in the same specific areas most of the time (raccoon latrines), so in general gardens probably aren't common sites for raccoon feces, although it certainly can occur. Cats are probably more likely to defecate in gardens. We shouldn't take concerns about Baylisascaris lightly, because even though disease (larval migrans) is very rare, it can be very severe.

Now, about testing cats for Baylisascaris - there's not much use, for several reasons:

1) The likelihood of a positive result is very low. The prevalence of Baylisascaris in dogs is very low. Little is known about the prevalence in cats specifically, but it is presumably very uncommon there as well.

2) It can be difficult to differentiate Baylisascaris from the feline roundworm, Toxocara cati. Unless the lab has experience with this, they may not be able to tell the difference. Therefore, you might get a misleading result.

3) What does a positive test tell you? It tells you that the cat is shedding this parasite or that is has ingested eggs that are just passing through the intestine.  The risk to people is still minimal if litterboxes are cleaned regularly. Contaminated stool is not infective until it has sat around for days to weeks, so regularly cleaning the litterbox and good handwashing can control the risk.

4) What does a negative test tell you? It tells you that the parasite was not detected on this single sample. It could have been there but not been identified. It might not be there today but could be there tomorrow (though this is still unlikely). A single negative test today does not tell you too much.

5) What would you do with the results? Probably not much. In the very unlikely chance that results were positive, it would likely be recommended to repeat testing to see if eggs are just passing through or whether the animal truly is infected with the parasite. That would determine whether treatment is needed. Otherwise, recommendations would be pretty much the same in both cases (good regular deworming program as directed by your veterinarian, proper handling of cat feces...).

The best way to prevent exposure of your cat to Baylisascaris (as well as other pathogens, predatory wildlife, vehicles, etc.) is to keep it inside.

Parasite exposure from pets

A recent study from the Netherlands investigated the prevalence of zoonotic parasites in pet feces and on pets' haircoats. The authors sampled feces and fur from dogs and cats, and looked for Toxocara (roundworms), Toxoplasma, Giardia and Cryptosporidium. All these parasites are of concern from a public health standpoint because they can be found in healthy pets and can also infect people.

Toxocara eggs were found on the haircoats of 12% of dogs and 3.4% of cats. Levels were low, ranging from 1-31 eggs per sample. An important aspect of this study was that they also assessed viability of these eggs, and found that none were viable.  Therefore, even though eggs were present, they were not relevant because they were dead. Exposure to UV light and lack of humiditiy were cited as possible reasons for the death of the eggs.

Toxocara were found in the feces of 4.4% of dogs and 4.6% of cats, which is consistent with other studies of healthy pets.

Toxoplasma was not found in the feces of any cat. (Cats are the hosts for this parasite so dogs weren't tested.)

Giardia was found in the feces of 15% of dogs and 13.6% of cats. However, when these strains were typed, the vast majority were species-specific types that do not cause disease in people. Only 2 of the 15 Giardia samples were assemblage A, a type that is transmissible from pets to people. This is very important to know because crude Giardia numbers don't tell you the whole story

Cryptosporidium was found in feces of 8.7% of dogs and 4.6% of cats. However, they were not able to type these parasites to determine if they were species that typically cause infection in humans, or whether they were Cryptosporidium felis or C. canis, which rarely cause disease in people.

The discussion section of the paper contains an interesting and relevant point about exposure to Toxocara eggs on the haircoat of pets. The authors state "Even in the worst case scenario of highly contaminated fur, e.g. with the highest Toxocara [eggs per gram] of 300 and an embryonated rate of 4% from the study of Wolfe and Wright, it is necessary to ingest more than 4 grams of hair, with 12 embryonated eggs per gram, to ingest 50 infective eggs."  Based on these data, exposure to parasites from the haircoat of pets is quite unlikely.  It might be a greater concern with stray or debilitated animals, or with puppies/kittens, who could have much greater coat contamination.

The take home message: Normal contact with healthy pets likely poses minimal risk of transmission of zoonotic parasites. That being said, regularly washing your hands is still a good idea because of the potential for exposure to other types of microorganisms (e.g. bacteria), and in rare circumstances where there may be large parasite burdens on a pet. Good deworming practices, particularly for puppies and kittens, also need to be considered.

Reference: Overgaauw et al, Veterinary Parasitology, 2009.

Are all Giardia created alike?

Giardia is a protozoal parasite that can cause diarrhea in multiple animal species. This microscopic parasite is a zoonotic pathogen that can be transmitted between animals and humans, and there are conerns about the role of pets in human disease.  Various studies have evaluated the presence of Giardia in healthy dogs and, to a lesser degree, cats. Typically these studies report that  about 7% of healthy dogs are shedding Giardia in their stool, but all Giardia are not the same in terms of the risk of transmission from dogs to humans. There are various types of Giardia, and some only infect specific animal species and not people. In dogs, assemblages (types) C and D are most commonly reported. These are considered canine-specific types and are therefore not a concern for transmission to humans. Assemblage A is an important zoonotic type which can infect dogs and humans, and this type can certainly be found in healthy dogs, but it seems to be relatively uncommon.

Emerging information about Giardia typing and zoonotic disease risks shows that this is a more complex issue than previously thought. Studies that determine the prevalence of Giardia shedding in dogs and cats are useful, but they only tell part of the story. Comments about the human health implications of Giardia shedding in pets can only be made when information about the Giardia assemblages found in these animals is also reported.

More information about Giardia can be found on the Worms & Germs Resources page.

Canadian parasite treatment guidelines for pets

Canadian Guidelines for the Treatment of Parasites in Dogs and Cats have recently been released. These guidelines were developed by an expert panel, consisting of six Canadian veterinary parasitologists and two private practitioners. They provide a good, balanced approach to the treatment of parasites, with an emphasis on the risks present in different regions and in different types of pets. There is very little objective information on which to base some of the recommendations, so many aspects are instead based on expert opinion, not necessarily hard facts, but when data are lacking, that's when opinions from independent experts are most needed. The guidelines provide an overview of recommended treatments along with an explanation of the reasoning.  This document is a useful resource for pet owners and veterinarians alike. There is also discussion about why guidelines in Canada differ from those in the US. To download these guidelines click here.

Note: Development of the guidelines was supported by a pharmaceutical company, but the information they contain was developed by the independent experts mentioned above.

Feeding wildlife: Bad idea

A recent question from a reader:

"We live adjacent to the Oak Ridges Moraine in Aurora (Ontario) so our property has always been popular to local wildlife.  For years, neighbourhood animals have enjoyed dry cat food in our backyard but the town has ordered this practice must stop immediately.  Among reasons given, were that this food is harmful to the animals.  This should be appropriate food for stray and feral cats but am writing to enquire if there is any information available about the effect of dry cat food on birds, raccoons and other domestic wildlife. Since the Premier declared Ontario free of the raccoon strain of rabies last year and there have been no recorded cases in York region, the main health concern is likely raccoon roundworm.  I understand that incidence is quite rare but, coincidentally, the recent articles about roundworm cases in New York led me to you. Can you recommend sources of information to learn if feeding dry cat food is harmful to wildlife (raccoons) and if this food would cause increased risk of raccoon roundworm in the immediate area."

This raises some very interesting points.

What are the bad points about feeding wildlife?
Wildlife is best kept wild. The more we feed wild animals, the more contact there can be with people. That can be dangerous, depending on the animal (e.g. coyotes). It can also bring disease-carrying wildlife in closer proximity to peoples’ living spaces, such as encouraging roundworm-shedding raccoons to live next to houses. If you feed raccoons and they decide to stay, you may end up with a highly contaminated raccoon latrine somewhere on your property. That could pose a particular risk if you have young children or developmentally delayed individuals at home.

The natural food supply is one of nature’s ways of keeping animal populations at appropriate levels. If lots of people feed wild animals, their numbers can increase, resulting in more exposure to people, increasing animal population density (with corresponding risks to the animals from disease transmission) and an unsustainable population should the "free food" source disappear.  It can also have a huge impacts on the local ecosystem of which we may not even be aware. Making wild animals dependent on humans is not a good thing.

Cat food is for cats. Dog food is for dogs. Neither of these necessarily provide appropriate nutrition for a raccoon, because dietary needs are different for each species. That being said, eating small amounts of pet food periodically likely doesn't do any harm to the raccoons.  However, if raccoons rely on pet food as their main food source, I wonder whether health problems could develop, because the animals may stop eating the foods they need to provide a balanced diet.
What does "raccoon-rabies free" really mean?

Raccoon rabies is a type of rabies virus (example of other types are bat rabies virus and skunk rabies virus). Raccoons can be infected by other rabies viruses, so even though Ontario may be free of raccoon rabies, the province is not necessarily free of raccoons with rabies. Raccoon rabies control efforts have been highly successful in Ontario, but it is important to be aware that raccoons can still carry rabies. Any feeding practices that encourage contact with raccoons (as well as skunks, foxes and other wildlife) are of concern because these animals can carry rabies, of one type or another.

Garden veggies and poopy parasites

Spring appears to have finally sprung in earnest in Southern Ontario (although we may still get one more frost on the weekend, so I hear) and people are getting back out into the garden.  An increasingly  popular trend in recent years, particularly this year now that the Obama's are doing it too, is vegetable gardening.  Lots of people like the idea of growing their own veggies in their own backyard, or perhaps in a community garden plot for city dwellers who still want to get their hands dirty - it's economical, good for the environment, and the plants can be grown "organically" without the use of chemicals or pesticides.  However, pesticides and garden bugs aren't always the only things to worry about having on your fresh veggies.  We received the following comment from a Worms&Germs reader:

"...What if veggies get infected with raccoon stool[?] Can eggs be killed after [the] veggie is grown and ready to eat?"

Great question.  The concern in the case of raccoon stool is the eggs of the roundworm Baylisascaris procyonis, which can be passed in huge numbers by a relatively high percentage of raccoons in many regions.  If swallowed, the eggs release larvae which can migrate through the tissues of the body, rarely causing visceral, ocular or neural larval migrans.

The good news:

  • Raccoons like to defecate in the same areas most of the time, usually on a relatively flat, elevated surface (e.g. woodpile).  These areas become raccoon "latrines", and the soil in the area can become very heavily contaminated with roundworm eggs.  The good part is that most raccoons therefore not defecate in your garden.
  • Vegetables cannot become "infected" by the parasite - the eggs cannot be absorbed or otherwise get inside a vegetable, they can only contaminate the parts of the plant that are directly in contact with soil.

The bad news:

  • Even though raccoons may not poop in your garden, they can still track roundworm eggs into the soil on their fur or paws when they come by to explore your crop, so you should always consider soil outside as potentially contaminated.
  • Baylisascaris eggs are highly resistant to disinfectants and chemicals, so they can't be killed this way.
  • Raccoon roundworms aren't the only parasites that may be found in garden soil.  Dogs and cats can carry other roundworms (Toxocara spp.) which are also capable of causing larval migrans if swallowed (although infection with these worms in dogs and cats is not nearly as common as infection with Baylisascaris in raccoons).  Cats in particular, unfortunately, do sometimes like digging in gardens and may sometimes use a garden as a litterbox.
  • Soil, particularly if it's contaminated by the stool of any animal, can also contain many different kinds of bacteria such as Salmonella.  Even if you can somehow protect your garden plot from animals, purchased garden soil and fertilizers may contain or may have come in contact with animal stool somewhere along the way.

So how do you make your garden veggies safe to eat?

  • Wash wash wash: Because Baylisascaris eggs are so difficult to kill, the best thing to do is physically remove them from all surfaces of your vegetables by washing thoroughly to remove all visible dirt before doing anything else.  If you cut into a vegetable before washing it, the soil on the outside can contaminate the inside.
  • Peel peel: Peeling vegetables ensures that all dirt (including any dirt stuck in tiny crevices on the vegetable's surface, or dirt you may not be able to see with the naked eye) is removed prior to consumption, but it's still crucial to wash the veggie first (and your hands) before peeling.
  • Cook: From an infection control perspective, it's best to cook vegetables before eating them.  This actually won't do anything to Baylisascaris eggs - these have to be removed by washing and peeling - but it does help kill bacteria that either contaminated the veggies out in the garden or that contaminated the veggies during their preparation in the kitchen.  For those of us who like our nice crunchy vegetables, obviously cooking them won't do, therefore washing and peeling become that much more important.

And, of course, always wash your hands thoroughly with soap and water after you've been working in the garden, even if you wear gloves.

In a lot of urban areas, it's hard to prevent raccoons and other animals from getting into yards and gardens.  There are things you can do to discourage raccoons from hanging around your house, and if raccoons establish a latrine on your property it must be very carefully cleaned up.  For more information on Baylisacsaris, raccoons and cleaning up raccoon latrines, please see our archives.

UK man campaigns to educate about Toxocara

A UK man is on a campaign to raise awareness about Toxocara, following an infection that blinded the child of a family friend. Mike Kennedy, chairman of the Grange Residents' Association, is  raising awareness about the importance of picking up "dog dirt" (i.e. dog stool).

Toxocara canis is an intestinal parasite that can be found in a small percentage (likely 2-14% in Ontario) of healthy dogs, and a larger percentage of puppies. Toxocara cati is the feline equivalent found in a comparable proportion of cats. If a person swallows an infective egg - an egg that was passed in an animal's stool and allowed to sit around in the environment for a while - infection can occur. The parasite can migrate throughout the person's body, causing various types of problems. Migration into the eye (ocular larval migrans) can cause blindness. Migration through the brain (neural larval migrans) can cause serious brain injury. These are very rare diseases, but are obviously still a concern because of they can be so severe. The risks are highest in children and people with developmental delays, since they're more likely to swallow stool, dirt, or something else contaminated with stool.

Mr. Kennedy's emphasis on educating animal owners to pick up after their pets is the key. We know a small percentage of dogs and cats shed Toxocara in their stool. You never know exactly who is shedding the parasite at any time, so removing the source of parasite eggs, the stool, is critical.  Deworming pets regularly is also important, but it is only one component of parasite control. The frequency and type of deworming needed for dogs and cats varies between regions and animals.  Your veterinarian can design an appropriate deworming program for your pet. Such a program requires a balance between adequate deworming to reduce the risk of parasites in pets (and the associated risk for human infection) and using dewormers prudently to reduce the risk of parasites developing resistance to these drugs.

Photo credit: Michael Lazarev (Clyde, the bulldog puppy)

Sandbox worms

I received this question the other day:

I just bought sand for a sandbox that I bought new 3 weeks ago. My granddaughter and I were playing in it and I came across some 2 inch long worms. I had a cover on my sandbox from day one so no animals got into it. I would like to know how to treat the sand without infecting my grandchildren and are these worms harmless.

We often use the term "worm" loosely when referring to different types of parasites.  An important point, however, is not all worms are parasites, and not all parasites are worms. Most worms that you find outside are just worms that have no relevance at all to human or animal health.

When it comes to concerns about "worms" and sandboxes, we're worried about roundworm eggs and hookworm larvae from the feces of infected animals. It's these microscopic eggs and larvae that are the problem, not any large worms you'd be able to see with the naked eye. Covering sandboxes is recommended to keep animals from defecating in them and contaminating the sand, but various types of non-parasitic worms can still certainly find their way into some outdoor sandboxes, even if they're covered.  I don't know of any human or animal health concerns regarding these kinds of non-parasitic worms. (I don't recommend snacking on worms from the sandbox to prove the point, but I would not be concerned about having worms in a sandbox).

More information about sandboxes can be found on the Worms & Germs Resources page.

Climate change and pet health

Recently, I made a few comments about climate change and the potential impact on infectious diseases in horses on our sister site, equIDblog. A recent news article in New Scientist discussed concerns about climate change and pets. The main infectious disease concern regarding climate change is changes in patterns and spread of insect-borne diseases, because different insect vectors may expand their normal ranges or change their seasonality in response to climate change. Some of the examples cited in the article include:

  • Babesiosis, a blood-borne disease spread by the European dog tick, is being found in areas of Europe where it was previously rare.
  • Increasing populations and ranges of ticks have been reported in many countries, which is a significant concern based on the number of different diseases these ticks can carry and transmit.
  • Leishmaniasis has been identified in dogs in the southern UK.  If climate change allows sandflies (the insect vector of this disease) to become established in the UK, then spread of this disease could become a major problem.
  • Milder winters may result in longer periods of activity of some insects that transmit disease, thereby extending the times of the year when there is a risk of disease. In some areas, year-round risk could develop for diseases that were previously seasonal.

Climate change is a complex and still rather controversial topic. Predicting the infectious diseases implications of climate change is difficult.  Information that is already available for some diseases, combined with general knowledge about microorganisms and their hosts, can help us make some educated guesses about what may happen. While the full scope of the impact cannot be predicted, it is almost certan that climate change will result in infectious disease challenges in both veterinary and human medicine.

Raccoon roundworm in New York

ProMed mail has a report about 2 cases of Baylisascaris procyonis infection in people in Brooklyn, New York.  Baylisascaris is the raccoon roundworm and is very commonly found in the intestinal tract of healthy raccoons. Raccoons shed this parasite in their stool, and after a short period of time, the parasite larvae become infective to other animals and people. Infective larvae can survive for a long time in the environment. People become infected by swallowing the larvae that can be found in dirt or on any object contaminated by raccoon stool. Disease in humans due to this parasite is rare but can be extremely severe.

The first case in this report involved an infant with neural larval migrans, a condition caused by migration of the roundworm larvae through the brain. Despite treatment, the child now has permanent brain damage because of this disease. Unfortunately, this is not uncommon consequence, as the infection is not usually identified until severe and irreversible damage has already occurred. The child had a history of eating soil, and swallowing soil contaminated with raccoon feces is the most likely source of infection.

The second case involved a 17-year-old with ocular larval migrans, which is caused by migration of the parasite larvae through the eye. The parasite was killed using laser therapy, however the patient lost all vision in the affected eye before the infection was identified. There was no mention of where or how the teenager may have been exposed. Infection of someone of this age is very uncommon, as most 17-year-olds are much less likely in ingest (intentionally or accidentally) raccoon stool. It would be useful to know whether this patient had a developmental disability which results in an increased likelihood of swallowing dirt or feces, or whether there may have been some other type of exposure.

Baylisascaris infections in people are extremely rare, despite the fact that a large percentage of raccoons carry this roundworm. This report of two cases occuring in the same area within a few months of each other is surprising.  Hopefully it's just a bad coincidence, and not an indication of some change in the incidence of this disease. Avoiding Baylisascaris means avoiding ingestion of raccoon stool. Sounds simple enough, but this is of particular concern with young children and people with developmental delays who are more likely to swallow contaminated dirt or stool, or put dirty/contaminated hands or objects in their mouths.

More information about Baylisascaris and preventing transmission of the infection can be found in our archives, as well as information about cleaning up raccoon latrines.

International Pooper Scooper Week

I guess there's now a week for absolutely everything. aPaws, the Association of Professional Animal Waste Specialists (no, I'm not making this up) has declared April 1-7 to be International Pooper Scooper Week. The overlap with April Fool's Day is apparently just a coincidence.  This group was formed in 2002 in recognition of "the growing problem in our communities, environment and water tables" associated with, yes, dog poop.

The American Pet Association estimates that over 4.4 billion pounds of poop are produced by the some-71-million dogs in the US each year. That's enough to cover 900 football fields with 12 inches of dog waste. (That is some deep do-do!)  Dog feces can contain a wide variety of bacteria and parasites, some of which can infect other dogs, and some of which can also infect people. The risk to people and other animals is greatly reduced by prompt removal of feces and proper disposal (i.e. stoop and scoop). It's a pretty simple concept: if your pet poops outside, pick it up. Use a plastic bag, seal it, deposit it in the garbage, then wash your hands (or use an alcohol-based hand sanitizer if you're out for a long walk and there's no sink handy). Most people are conscientious about this, but one look around most parks will show you that not everyone is (and unfortunately that can give those of us who do stoop and scoop a bad name!).

Photo source:

Dog park closed because of bleach contamination

A dog park was closed because of an attempt by a dog-owner to disinfect puddles.  The woman was seen pouring a gallon of bleach into a mud puddle, sparking an investigation. The site was closed while city staff pumped out puddles. The woman told the person that witnessed and reported the incident that her dog had contracted the intestinal parasite Giardia in the park, and she was trying to sanitize the water.  However, authorities believe it may in fact have been a malicious act (i.e. an attempt to poison the dogs using the park).

  • Firstly, there's no way the woman could know that the park (let alone a specific puddle) was the source of her dog's infection. Giardia can be found in the environment and in the stool of a small  percentage of healthy dogs (~7% in many studies).
  • Secondly, pouring a toxic substance into the puddles in the park is obviously not an appropriate response. Bleach is a good disinfectant when it's used right, but disinfecting outdoor surfaces like this is essentially impossible. Organic debris (e.g. mud) will readily inactivate bleach, but the bleach could still make an animal sick if too much (too high a concentration) is swallowed, because it's very caustic.
  • Thirdly, for this woman to take matters into her own hands like this without consulting  someone who knows something about infectious diseases, and potentially exposing a lot of animals to high levels of bleach is irresponsible. If there was concern about the park as a source of infection, the appropriate response would have been to talk to city staff.

In reality, the risk to other dogs was probably pretty low. It’s pretty obvious when there's a lot of bleach somewhere (even just based on the smell), and in general dogs would probably be very reluctant to drink bleach-contaminated water.

One officer stated that he suspects the Giardia story was an excuse contrived by the woman when confronted by the passer-by who witnessed the bleaching incident. That’s certainly possible, but I’m surprised someone would come up with a specific excuse like Giardia.  If the woman is found, that should be easy to figure out - the diagnosis would have to be in her dog's medical record.  Police stated that the woman, if identified by the authorities, could potentially face animal cruelty charges. I think that’s pretty unlikely, considering what usually has to happen for someone to actually be charged and convicted of animal cruelty. I suspect this really was an overzealous response by someone who lacks common sense. There was no comment about whether the woman would be billed for the city staff time required to deal with the clean up - that might be a more effective deterrent to similar incidents in the future!

Parks are inherently a high-risk environment for exposure to infectious diseases. Whenever you mix large numbers of animals, especially in an area where they often pass stool, there is an increased risk of disease transmission. You have to accept that when going to a park. People should also ensure that they never take a sick animal to a park, promptly clean up stool, and may sure that their pet is on an appropriate vaccination and deworming program. Disinfection of a park will never be part of the infection control program.

More information about Giardia can be found on the Worms&Germs Resources page.

Sandbox season arrives!

We've had some beautiful warm days in southern Ontario lately, and spring - technically - arrives tomorrow (despite the fact that it's been trying to snow in Guelph even this afternoon!  But hope springs eternal (pardon the pun)).  The picture (right) is Erin, my youngest daughter, enjoying the warmer weather and playing in a sandbox at my parents' house yesterday. Allowing a child to play in the sand carries some degree of infectious disease risk, but the risk is very low and simple measures can reduce the risk even further.

The main diseases of concern with regard to sand in temperate regions (like Ontario) are spread via the fecal-oral route, meaning the diseases are transmitted by swallowing organisms that are passed in the stool. The most important of these diseases - visceral larval migrans and ocular larval migrans - are caused by parasites. These disease are uncommon in most places, and when they do occur they're not typically associated with sand from sandboxes specifically. However, while very rare, larval migrans can be a very serious condition. The risk is greatest in very young children and children with developmental problems who are more likely to eat sand. In warmer (more southern) regions, another parasitic disease called cutaneous larval migrans is much more common.  This condition can occur after just skin contact with contaminated sand.

The main points regarding sandbox safety are:

  • Keep sandboxes covered so animals don't use them as litter boxes.
  • Check the sand regularly to make sure there is no evidence of animal stool or urine.
  • Try to prevent children from putting their hands, or other objects, in their mouths while playing in a sandbox (and in general!).
  • Don't give children snacks or drinks while they're playing in the sand.
  • Wash (or make sure they wash) children's hands after they're done playing in the sand.

For the average child, the risks of infectious diseases from sandboxes are extremely low.  I have no problem letting my children play in the sand... I just use these basic infection control precautions.

More information on sandbox safety can be found on the Worms&Germs Resources page.  More information on larval migrans is also available in our archives.

Research finds 10% of dogs may make their owners sick

This rather sensational title is from a Murdoch University (Australia) news article regarding a study of intestinal parasites in Australian dogs. It certainly grabs one's attention. For me, the article brings to mind two different trains of thought:

1) Far more than 10% of dogs could make their owners sick.  Be it dogs, cats, rabbits, iguanas or anything else, every pet is carrying something that could cause an infection in a person in certain situations. If a study says that only X% of dogs/cats carry some sort of zoonotic pathogen (and X isn't 100), then they didn't test hard enough or they didn't test for enough things. Every animal - and every person - is carrying something that can make others sick. However, even though all pets carry zoonotic pathogens, most of these are of minimal concern to most people, and therefore the likelihood of most pets making their owners sick is relatively low. We have to remember, however, that there is no such thing as "no risk" pet contact, just as there's no such thing as "no risk" contact between people.

2) The 10% figure from this study refers to the percentage of dogs that were shedding the intestinal parasite Giardia. This parasite can cause disease in people and that's why there is concern. However, the 10% figure isn't really surprising, as the press release states, because previous studies from different areas in the world have reported Giardia shedding by 7-10% of healthy dogs. The real question is, what is the risk to people from these dogs? The short answer is: we don't know. Not all types of Giardia found in dogs are able to cause disease in people. Figuring out what type of Giardia a dog is shedding requires fairly specialized testing, and there's no indication that this was performed for this study. If most dogs carry strains that don't infect people, then the risk is very different than if most dogs were carrying zoonotic strains.  Furthermore, we don't know how often Giardia is transmitted between people and pets in any situation. At this point, there is actually very little information regarding transmission of Giardia from pets to people. That being said, it's better to err on the side of caution and assume that Giardia could be transmitted from pets to people, at least until we have good evidence otherwise.

I'm not trying to dismiss the potential concerns about Giardia in dogs, nor do I think the study isn't useful. It's an interesting study that has provided new information about intestinal parasite carriage in dogs in Australia. However, it doesn't really tell us anything new about the risk to humans.

Professor Andrew Thompson, Murdoch's Head of Parasitology gives some good advice when he states "As a result of these new findings, dog owners should be aware of the signs of Giardia and how to prevent infection in their pets. If you suspect that your dog may be infected with Giardia, it is important you visit your local vet for a full diagnosis.”

More information about Giardia can be found on the Worms&Germs Resources page.

Photo: Giardia trophozoite (CDC Public Health Image Library #8698/Janice Carr)

Lungworms in dogs: Parasite risk or marketing ploy?

I read a press release today entitled "New Parasite Infection Killing Pet Dogs in Southern England". It's about the lungworm Angiostrongylus vasorum. The main reservoir for this parasite in England is the common red fox. Slugs and snails are involved in transmission of the worm as well.  Infection of dogs most likely occurs through ingestion of the parasite from contaminated water or other environmental sources. The press release mentions a study that was released last year which reported an increase in the parasite in wild foxes. It mentions (without providing any data) that infections are occurring regularly dogs in some regions. This may well be true but brings to mind an important point I mentioned the other day (among others): know the source of information you are reading. I know I'm being a bit cynical, and it's possible that they have the well being of pets in mind, but the press release is from an online veterinary pharmacy, a company that obviously benefits from increased treatment of pets with dewormers.

This is made clear by their statement "Luckily there are a number of medicines available that can provide real and lasting protection from this nasty parasite. At we recommend that all dog owners make it their business to find out about this disease and make sure that their dogs are fully protected."

Is lungworm a real and increasing threat in the UK? It's certainly possible. I don't dismiss the possibility at all.

Would I get concerned about it at this point? No. I'd look for objective information and ask my vet if there are any concerns in my particular area. Like the press release says, people should "make it their business to find out about this disease."

So what does this tell me? It reminds me that there are a lot of potential infectious disease threats out there that I need to pay attention to, but there are also a lot of people trying to make money at the same time. It could be that this company is being benevolent and honestly trying to make sure that pet owners are aware of the risks of lungworm. It's also possible they are taking advantage of a marginally relevant problem. Information like this is good for raising some questions, but getting advice from a non-biased source is critical.

Deworming kittens and puppies

Deworming adult cats and dogs is a rather controversial area at the moment. Balancing concerns about animal health, zoonotic disease transmission, drug resistance, compliance and cost is difficult. Risks vary between different regions/climates and there are no clear answers. One area that is much less controversial is deworming of kittens and puppies (less than 6 months of age), as there is general consensus that aggressive deworming is needed in these animals.This is because young animals are much more likely to harbour parasites. They are also more likely to contaminate the household environment during the litter/house training process and tend to have very close contact with people. The greatest concern tends to be about roundworms, since they are very common in dogs and cats (especially young ones) and zoonotic infections  can occur (i.e. visceral and ocular larval migrans, similar to that caused by the raccoon roundworm, Baylisascaris procyonis).

Standard deworming guidelines are:

  • Puppies should be dewormed at 2, 4, 6 and 8 weeks of age, then monthly until 6 months.
  • Kittens should be dewormed at 3, 5, 7 and 9 weeks of age, then monthly until 6 months.

Further treatments depend on various factors, including the animal's lifestyle (risk of exposure), how common different parasites are in the region and perhaps whether there are high-risk people in the household. Your veterinarian can provide the best advice for your individual pet.

Another thing to remember is that not all parasites are killed by all dewormers. Specific deworming programs need to be set up to address different parasite risks.

More information about roundworms (and other parasites) in dogs and cats can be found on the website of the Companion Animal Parasite Council, an industry-funded organization.

Photo: A large mass of roundworms from the intestine of a heavily infected animal.

Some Beach, Somewhere

"Some Beach, Somewhere" is not only a popular country music song AND the name of one of the best Standardbred racehorses in the world (originally Canadian, no less!), it's also the prime source of infection for a disease called cutaneous larval migrans.

Cutaneous larval migrans is a skin disease caused by migration of hookworm larvae. The most common hookworm species involved is Ancylostoma braziliense, which can be shed in the stool and dogs and cats. Ancylostoma caninum  and A. tubaeforme are other species of hookworms that parasitize dogs and cats, respectively, and can also cause the disease, but much more rarely.

Animals infected by the hookworms shed hookworm eggs in their stool. These eggs then develop into larvae, and people become infected through skin contact with hookworm larvae in the environment, particularly in sandy areas like beaches where infected animals may have defecated.

Cutaneous larval migrans is characterized by a "serpiginous (snake-like) rash" that is intensely itchy (see picture left).  This is caused by the parasite larva burrowing through the skin. In North America, the disease is most common in the southeastern US and the Caribbean. Most , if not all, cases in people in Canada are associated with travel, especially to Caribbean countries; they presumably caused by exposure to hookworm larvae on the beach. Ancylostoma braziliense is not found in Canada.

The best means of controlling cutaneous larval migrans are to promptly remove dog and cat stool from the environment and dispose of it in the garbage, and to regularly deworm dogs and cats. This is important in areas where A. braziliense is endemic, but is easier said that done in areas where feral (wild) dogs are common.

Photo source:

Echinococcus on the rise in Bashkiria, Russia

Echinococcus granulosus, the cause of hydatid disease/hydatosis in people, is on the rise in the Bashkiria (Bashkortostan) region of Russia. Fifty-three cases were identified in Bashkiria in 2008, 1.7 times the number of cases reported the year before. Over 500 cases of human infection with Echinococcus are reported in Russia annually.

The original article (translated from Russian) states that the people at risk are those in contact with cattle and other domestic animals. Echinococcus actually causes the same type of disease in cattle and livestock as it does in people – it forms slow-growing cysts in the lungs, liver or other tissues. When the cysts are small they usually don’t cause a problem, but eventually (sometimes even years later) they can grow to a size that interferes with normal organ and body functions. However, people do NOT become infected by contact with cattle, sheep or other intermediate hosts. The infection can only be spread to humans (and livestock) by the definitive host - dogs, including domestic dogs and wild canids. In dogs, the parasite lives in the intestine in the form of a tiny adult tapeworm, and the tapeworm eggs are shed in the dog’s stool. When the eggs are swallowed by an intermediate host, the immature form of the parasite penetrates the intestinal wall and migrates through the body tissues to the site where it ultimately forms a hydatid cyst. If the animal dies or is killed, and the cyst is eaten by a dog, then the cycle begins again.

The most probably reason for the increased number of human infections in this case is an increase in the number of dogs in the same area, particularly those used for herding sheep. This may be equivalent to the dog-reindeer cycle present in Siberia.  Echinococcus infection in dogs can be treated with common deworming agents that kill other tapeworms, but it is likely that dogs in these areas are not dewormed as often as they should be to prevent this disease.

The article reiterates some sound recommendations for decreasing the risk of Echinococcus infection. These may sound familiar, because many of them also help decrease the risk of transmission of infectious diseases in general:

  • Wash your hands after contact with animals.
  • Wash your hands after working in orchards where cattle have wandered (not the most widely applicable recommendation for people living in North America, but is along the same lines as our recommendation to wash your hands after working outside, particularly with soil).
  • Do not consume unwashed greens or vegetables (all fruits and vegetables should be thoroughly washed with potable water before being processed or eaten).
  • Do not drink water from untreated sources.

More information about Echinococcus and other tapeworms is available in the Worms & Germs Archives.

Photo: Central Asian Shepherd Dog (Sredneaziatskaya Ovcharka), click here for source (Wikipedia).

Cheyletiella - The walking dandruff

Cheyletiella is a genus of mites that commonly affect dogs (C. yasguri), cats (C. blakei), rabbits (C. parasitovorax), and occasionally people.  Unlike Sarcoptes species (the mites that cause sarcoptic mange), these mites live on the surface of the skin and do not burrow into deeper layers.  They feed on dead skin cells and occasionally tissue fluid.  Infestation with these mites can be very itchy, but not always.  Cats in particular can carry the mites without any visible abnormalities of their skin or fur.  Typically, however, the affected animal's fur becomes crusty, scaly and inflamed, and sometimes patches of fur may be lost.  The mites are usually a little less than a half-millimetre long (so they are visible to the naked eye if you look closely) and grayish-white.  They tend to be quite active and crawl around (but they don't jump like fleas), which gives them the appearance of walking dandruff.  Diagnosis is easy if the mites are seen strolling around on a table or blanket, otherwise they may be found on a "scotch tape test" or superficial skin scraping.

People can be affected too if they have close contact with a pet carrying Cheyletiella.  Lesions, which usually take the form of single or grouped small red bumps on the skin, typically appear on the arms, trunk or thighs, and sometimes can be extremely itchy!  It is rare to see the mites themselves on a person - usually they're found on the pet.  The good news is these mites can't actually complete their life cycle or survive for long on people, and in the environment even the hardiest forms of the parasite (usually the eggs and adult females) die within about ten days.  So once the source of the mites is eliminated (by treating the pet with an appropriate anti-parasitic drug which your vet can prescribe), the signs in any affected people will resolve on their own without specific treatment (but you might want something for the itch!).

Photo: Light micrograph of C. yasguri from a dog (credit: Dr. M. Dryden, College of Veterinary Medicine, Kansas State University)

Tritrichomonas fetus in cats

I had an advice call the other day about control of Tritrichomonas fetus in cats. This protozoal parasite is being recognized as an important cause of diarrhea in cats, particularly in crowded situations such as catteries. In addition to the standard discussion about control of this parasite in cats, the question about human risks was raised. Tritrichomonas fetus is passed in the stool of infected cats, and other cats become infected by ingesting the organism. It is certainly possible that someone with an infected cat could be exposed to this parasite through inadvertent ingestion of the parasite following contact with infected surfaces (e.g. the cat's fur or litter box). Although this sounds gross, it probably occurs more often that we think. We encounter bacteria of fecal-origin regularly throughout the day.  Keep that in mind the next time you don't want to be bothered washing your hands

The risk of human infection with T. fetus is unclear, but is probably quite low. There is only one report of human infection by this parasite, and the person was immunosuppressed. Risks to healthy people are probably very low but we can't say there is no risk. Basic hygiene measures (especially hand hygiene and good litter box management) should reduce the risks even further. People with weakened immune systems should take greater care (because of the risks from this organism and many others), but still, common sense practices are the key.  More information about household infection control and litter box management for cat owners is available on the Worms & Germs Resources page.

Some excellent information on Tritrichomonas fetus can be found on the website of Dr. Jody Gookin, a leading researcher in this field.

Hurray for Winter - Mother Nature's Infectious Disease Control

The weather outside is frightful (at least up hear in Canada!) - it’s getting colder, the weatherman now warns us about “flurries” instead of “showers”, there’s frost on the cars in the morning, and we’ve all had to start putting on those extra bulky layers before leaving the house in the morning. There's lots of grumbling about the oncoming winter weather. Let’s take a look at the silver lining though – people who live at more northern latitudes often don’t appreciate what a few months of cold weather does for us!

Insects in particular, including mosquitoes, ticks and others that transmit various diseases, are almost entirely inactive outdoors when it’s cold outside. Many insect species can’t even survive Canadian winter weather, which is why they are only concerns in more southern climates. For example, the brown dog tick (Rhipicephalus sanguineus), which can transmit many diseases including canine babesiosis, anaplasmosis, and Rocky Mountain Spotted Fever (RMSF, which can also be transmitted to people), doesn't exist in Canada except on dogs that have travelled to the south.  The cold weather also helps keep heartworm in check through mosquito control - the prevalence if heartworm in North America decreases dramatically the farther north you go.  Bacterial pathogens are often good at surviving in the cold, but many are killed by freezing, and even if they can survive, it is almost impossible for bacteria to grow and multiply in the cold. Winter provides a reasonable knock-down effect for a lot of pathogens and parasites that often thrive in the outdoor environment during the summer months.

Of course, microbes and insects can still survive in the same environments where we do over most of the winter – indoors, where it’s nice and warm. So it’s still important to do things like wash your hands after handling your pet and before you handle food. And, as always, come spring we’ll have to be prepared for the return of all those worms and germs as we venture back to our favourite warm-weather outdoor activities.

In the meantime, grumble though we may, try not to give old man winter too hard a time – a few months of freezing temperatures isn’t all bad afterall.

Cleaning up raccoon latrines

Raccoon latrines are a major source of eggs of the raccoon roundworm, Baylisascaris procyonis.  Accidental ingestion of large numbers of eggs from these latrines can lead to a disease known as visceral larval migrans.  The most severe forms of this condition are known as ocular or neural larval migrans, which are damage to the eyes or brain/spinal cord (respectively) due to the roundworm larvae migrating through the body tissues.  The disease is very rare, but the consequences are very severe.  Previous Worms & Germs posts have discussed Baylisascaris and larval migrans in more detail.

Raccoons tend to form latrines - areas where they will return to deposit stool repeatedly.  In some ways this is handy, because it means you generally don't find raccoon stool all over the place.  On the other hand, the latrines themselves contain large amounts of stool, and along with that are large numbers of Baylisascaris eggs, not to mention bacteria and sometimes fungi.  So it is important to recognized latrines, particularly when they occur near your house, garden, or anywhere children may play.  Raccoons like to used flat, raised areas for latrines, such as roofs, decks, woodpiles, fallen logs or even large rocks, just to name a few.

Cleaning up raccoon latrines warrants some special precautions in order to avoid swallowing the roundworm eggs and to avoid spreading them around.  Recommendations include:


  • Wear rubber gloves, and always wash your hands thoroughly when you are done.
  • Wear disposable overboots, or rubber boots that can be scrubbed and disinfected.
  • Wear an N-95 rated particle mask if you are cleaning up a latrine in an enclosed space, such as an attic or crawl space.
  • Thoroughly wash your clothes with soap and hot water when you are done, and dry them completely.

Follow this link for detailed information on how to clean up a raccoon latrine.  A few of the more important points about dealing with these latrines include the following:

  • Avoid stirring up dust.  Misting the area with water first can help with this.
  • Double-bag and carefully dispose of any garbage/debris you remove from the area.
  • Most chemicals will not kill roundworm eggs.  Removing the eggs is usually the best option, but extreme heat will also kill eggs instantly.  Flaming contaminated areas can be effective, but contact your local fire department about local regulations and safety precautions before attempting to flame a latrine site.

More about Echinococcus tapeworms in dogs

Echinococcus granulosus is a tapeworm of dogs that causes a condition known as hydatid disease or hydatidosis in humans.  The parasite is found in many parts of the world, and is very common in some regions of southern South America, the Mediterranean, the Middle East, southwestern Asia, northern Africa and Australia.  To the best of our knowledge, E. granulosus does not occur in southern Ontario, but it is present in other parts of Canada including the western provinces and northern Ontario.  A related, but much nastier, tapeworm called Echinococcus multilocularis is much less commonly found in North America.

A previous Worms & Germs post described what is known as the sylvatic cycle of Echinococcus granulosus, which is thought to be a common route of infection for dogs in Canada.  In the sylvatic cycle, dogs become infected with Echinococcus by eating the internal organs (usually lungs and liver) of wild game such as moose and caribou.  The dogs then pass tapeworm eggs in their stool, which can cause infection in other wild animals (thus continuing the cycle) or in people who accidentally swallow the eggs.  In humans, Echinococcus forms slow-growing cysts (called hydatid cysts) in different organs of the body which can be very difficult to remove or treat in some cases.

Echinococcus also has a pastoral or domestic cycle.  In this cycle, dogs acquire the parasite by eating the internal organs of infected sheep, and sometimes other livestock such as cattle and swine.  This cycle is potentially very important in areas where there is a lot of sheep farming.  In some areas of Latin America, 20-95% of sheep at slaughter may have evidence of hydatid cysts in their organs.

It is much more difficult to tell when a dog is infected with Echinococcus compared to other tapeworms such as Taenia or Dipylidium.  An adult Echinococcus is tiny - only a few milimetres long (see picture right), very unlike the long, stringy white tapeworms that most people picture.  Dogs can carry hundreds, even thousands of these tiny tapeworms without showing any signs of illness at all.  The eggs can sometimes be difficult to detect on fecal examinations, and when they are seen they cannot be differentiated from Taenia eggs.  Nonetheless, this is still the best way to detect infection, so fecal examinations should be performed regularly.


  • In areas where Echinococcus is known to exist, it's important to have your veterinarian perform fecal examinations on your dog's stool more frequently than the usual once-a-year, because of the serious zoonotic potential of this parasite.
  • Always wash your hands well after handling dog stools.
  • Do not let your dog eat uncooked meat, or the organs from farm animals or wild game.

For more information on Echinococcus, see Worms & Germs post entitled Echinococcus and hydatid disease - not your average tapeworm.  There is also information available on the Michigan State Department of Natural Resources site.

Lower photo credit: Ontario Veterinary College

Your mother was right! Wash your hands

You may notice a recurring theme in many of our posts and on virtually all of the information sheets on the Worms & Germs Resources page: an emphasis on handwashing. There is increasing emphasis on hand hygiene (i.e. hand washing and use of alcohol hand sanitizers) education in hospitals because the hands of healthcare workers are a major (if not the most important) means of disease transmission between patients. Despite hand hygiene being easy, cheap and effective, people rarely wash their hands as often as they should, and they often don't do it properly.

Most of the research about hand hygiene that has been published has focused on its use and impact in human hospitals, but this area is now also being studied more with regard to animals and veterinary medicine. A study published earlier this year in Veterinary Microbiology provided more evidence that hand hygiene is a critical infection control measure when dealing with animals. The study, coordinated by Dr. Maureen Anderson (of Worms&Germs fame) looked at MRSA carriage rate in veterinarians who work with horses. In addition to finding a high rate of MRSA carriage among these veterinarians (which was consistent with other reports indicating that equine vets are at higher than average risk for exposure to MRSA), the study looked at factors associated with MRSA carriage. Vets that reported routinely washing their hands between farms and those that reported washing their hands after contact with potentially infectious cases had a significantly lower rate of MRSA carriage. That should come as absolutely no surprise, but it's one more piece of evidence that we need to pay more attention to this routine infection control measure, in human hospitals, in veterinary environments and in households.

Remember, the 10 most important sources of infection are the fingers on your hands!

Click here for instructions on how to wash your hands properly.

Updated: Speaking of Baylisascaris...

This post has been updated with new information as of October 2, 2008.

An article was published on Sunday in a local Guelph newspaper about a 14-month-old child who has been battling infection with Baylisascaris larvae in a Hamilton (Ontario) hospital for the last two weeks.  This comes on the heals of a very recent Worms & Germs post about Baylisascaris procyonis - the raccoon roundworm.

The disease caused by migration of Baylisascaris larvae through the body - visceral larval migrans - is uncommonly diagnosed in North America, although it may be more common than we think because it is difficult to diagnose with certainty, and the signs in mild cases may be very non-specific.  The most severe form of the disease is called neural larval migrans, which occurs when the larvae migrate through the brain or spinal cord, as in this most recent case.

The parents of the toddler in the article, a toddler who is still blind and cannot sit up on his own as a result of his infection, have a message for parents: keep raccoons out of your yard and away from your house.  The disease may be rare, but the effects can be devastating, and the risk can be significantly reduced by a few simple steps:

  • Keep garbage in tightly-sealed containers.
  • Clear brush and seal openings in buildings where raccoons may nest or form latrines.
  • If you find raccoon stool or what appears to be a raccoon latrine on your property, clean it up very carefully.  Follow this link for more information on identifying and cleaning up raccoon latrines.
  • Always wash your hands well after you've been working outside in soil, dirt or water which could be contaminated with raccoon feces.

For more information, see the last Worms & Germs post about Baylisascaris.


If you are looking for an interesting website to play around with, you should try HealthMap. This is a website created by the Harvard-MIT Division of Health Sciences and Technology that maps infectious disease reports from various sources. You can search by region and see what disease problems have been reported recently, or select specific diseases and find out where they've been reported.   Some examples are shown below. The top image shows all disease reports worldwide (in the last 30 days), while the bottom image shows reports of Salmonella in North America during the same time period. The site relies on reports of diseases (many cases of various diseases occur but are never reported), so it focuses mainly on outbreaks or high profile cases , but it is still quite interesting.

Above: All reported disease outbreaks/cases worldwide in the last 30 days.
Below: Reported outbreaks/cases of Salmonella in North America in the last 30 days.
See the HealthMap site for more details.

Updated: Raccoon Roundworms - Baylisascaris procyonis

This post has been updated with new information as of October 2, 2008.

Raccoons, just like dogs and cats, can have roundworms in their intestine. Dogs are typically infected by the species Toxocara canis, and cats are infected by Toxocara cati. Raccoons are infected by a type of roundworm from a different genus, called Baylisascaris procyonis. There is one thing that all three of the parasites have in common – the larvae of these worms can infect humans, causing a condition called visceral larval migrans.

Dogs and cats are usually dewormed as puppies and kittens, and often as adults as well, which dramatically decreases the number of pets that are infected with roundworms. Raccoons are not so lucky – in the northern and northeastern parts of North America, over 70% of raccoons may be infected with Baylisascaris.  In Ontario, it has been estimated that only about 20-30% of raccoons are infected, but usually with high numbers of worms. In either case, younger raccoons are even more likely to be infected.  Infected animals may shed millions of parasite eggs in their stool, and the eggs can survive in the soil for months or even years.

After a few weeks, the eggs in the raccoon stool become infective. If a person swallows the eggs, they hatch in the small intestine and release larvae. These larvae can then burrow through the wall of the intestine and migrate through tissues all over the body, causing tissue damage and inflammation. The signs of illness are often not very specific, and may include things like fever, fatigue and nausea. If the larvae migrate through the brain or spinal cord, a person may develop neurological signs like loss of coordination and muscle control. This is called neural larval migrans, which is the most serious type of disease caused by these larvae.  If the larvae migrate through the eye, they can cause blindness.  This condition is known as ocular larval migrans.

There have been less than 25 cases of confirmed visceral larval migrans due to Baylisascaris in the USA as of 2003, but the condition is very hard to diagnose with certainty, and it is possible that many cases are mistaken for other illnesses. The disease is also very difficult to treat, and neurological damage from neural larval migrans is usually permanent, so the best thing to do is prevent infection in the first place. Here are some tips on avoiding Baylisascaris:

  • Avoid contact with raccoons. Many people think raccoons are cute, but they are wild animals. Raccoons are also a risk for transmission of rabies if a person is scratched or bitten. NEVER keep a raccoon as a pet.
  • Discourage raccoons from hanging around your house. Clear brush and seal access to basements and attics where raccoons may try to nest or form latrines. Keep garbage in tightly-closed garbage cans. Eliminate outdoor water sources.
  • Always wash your hands well with soap and water after working with soil (e.g. in the garden).
  • Clean up raccoon latrines.  This must be done very carefully - avoid getting any raccoon stool on your hands or clothes. The stool should be burned, buried or sent to a landfill. Clean the area where the stool was found with boiling water. Wash your hands very carefully when you’re done.  Follow this link for more detailed information on how to identify and clean up raccoon latrines.

Baylisascaris procyonis less commonly infects animal species other than raccoons, including skunks, and it has even been found in dogs.  It's important to have your dog's stool examined for parasite eggs on a regular basis (typically once or twice a year) and to follow your veterinarian's recommendations for deworming your dog.

More information about Baylisascaris is available on the CDC’s Baylisascaris Infection website.

Echinococcus and hydatid disease - not your average tapeworm

A previous Worms & Germs post talked about the (very low) zoonotic risk of the tapeworm most commonly found in dogs and cats, Dipylidium caninum. Dogs can also carry other species of tapeworm, such as Taenia pisiformis, which cannot be naturally transmitted to people. But dogs can also carry tapeworms from the genus Echinococcus, the most common of which is E. granulosus. Echinococcus multilocularis is much less common in North America, and can also be carried by cats.

In Canada, dogs tend to be exposed to E. granulosus when they eat certain animals, particularly wild herbivores like moose and caribou. In other parts of the world, eating sheep organs is the most common way dogs are exposed.  The immature form of the worm is found in the animal’s lungs, liver and other tissues. After being eaten by the dog, the worm matures in the intestine, and tapeworm eggs can soon be found in the dog’s stool. Tapeworm segments, as seen with Dipylidium infection, are usually not seen in the stool with Echinococcus. Under a microscope, it is possible to tell Dipylidium eggs from Echinococcus eggs, but it is not possible to tell Echinococcus eggs from Taenia eggs.

If a moose, caribou, sheep or another suitable “intermediate host” swallows the eggs from the dog stool, the parasite migrates through the animal’s body and forms cysts in various tissues which contain the immature form of the worm. If the animal dies or is killed, and a dog (or a wolf or coyote or related species) eats the cysts, the cycle begins again.

Unfortunately, humans can also be an “intermediate host” for these tapeworms. If a person ingests Echinococcus eggs from dog stool, the parasite can form cysts (called hydatid cysts) in many tissues and organs, including the liver, lungs, brain and heart. If the cysts are small and there are only a few, they may not cause any problems for years, and the person may never know they’re there. But as the cysts grow, they can get very large and start to interfere with the function of organs, or their size alone may be a problem, depending on where they are located. Treatment can be difficult – drugs are frequently not effective, and large problematic cysts may need to be surgically removed, if the surgery can be done safely. If a cyst bursts it can cause anaphylactic shock, which is very dangerous.

In Canada, Echinococcus infection and hydatid disease are most common in the western provinces. Nonetheless, everyone can take a few simple steps to help prevent exposure of people to Echinococcus:

  • Always wash your hands after handling dog stool, even if you use a plastic bag or a scoop to pick it up.
  • Your dog should have a fecal examination for intestinal parasites at least once per year, or more frequently if your dog is at increased risk of exposure to Echinococcus. If tapeworm eggs are identified, your veterinarian can prescribe medication to treat the infection.
    • Monthly heartworm preventatives that are effective against other intestinal worms are not effective against tapeworms!
  • Do not let your dog eat uncooked meat, especially the organs of sheep or wild game such as moose and caribou.

More information on Echinococcus and hydatid disease is available on the CDC’s Echinococcosis webpage.

Banning Bowser from the beach

Many dog owners love to take their canine companions to the beach with them during the summer. Unfortunately, other people (particularly non-dog owners) sometimes take exception to having Bowser on the beach. These individuals often cite potential infectious disease risks as a reason to ban dogs from the beach.

While there are some potential infectious disease risks associated with having pet dogs at the beach, they are minimal. Also, some simple, common-sense steps can greatly reduce the risks that do exist. The infectious disease risks from feral (wild) dogs and wildlife defecating in the sand are much greater.

  • The biggest health risk is actually probably from dog bites. Bites can be avoided through proper handling and training of dogs that are brought to public beaches.
  • Many different bacteria (e.g. Salmonella, Campylobacter) can be passed in the stool of even healthy dogs. Some of these can be harmful to people, but only under certain circumstances, such as if they are swallowed or if they contaminate an open wound.
    • Promptly picking up any stool passed by a dog greatly reduces the risk of significant contamination of the sand. Also, sunlight is an excellent “disinfectant” and will help kill any residual bacteria left behind.
  • Dogs can also have different kinds of zoonotic parasites in their stool.
    • Some of these parasites (e.g. roundworms, hookworms) are passed in a form that takes days to become infectious to people. So promptly removing dog stool from the beach minimizes the risk of transmission.
    • Other parasites, such as Giardia, are immediately infectious when passed in the stool, but must be swallowed to cause infection. Prompt removal of dog stool, good hand hygiene with soap and water or an alcohol-based hand sanitizer before eating, and avoiding sand contamination of food and drink should largely eliminate this risk as well.

Overall, the risks of having dogs on beaches are very low if people behave responsibly, specifically properly restraining their dogs and promptly picking up stool.

More information about zoonotic diseases associated with contamination of sand and Sandboxes is available on the Worms & Germs Resources page.

Water Foul - Cryptosporidiosis

Cryptosporidiosis is a diarrheal disease caused by several species of the genus Cryptosporidium, which are single-celled parasites. The disease can cause severe diarrhea.  It tends to make the news when outbreaks occur associated with contaminated drinking water, but outbreaks only account for the minority of cases reported each year. Infection can be very serious (even fatal) in immunocompromised individuals, such as HIV/AIDS patients, but even immunocompetent (i.e. otherwise healthy) people can get sick. Different animals have their own species of Cryptosporidium. It is still unclear which of these species can normally infect people as well, and make them sick. Frequently cats and dogs with Cryptosporidium don’t look sick. Here are some facts:
  • Cryptosporidium hominis primarily infects humans. Clearly it can make people sick, whether their immune systems are weakened or not.
  • Cryptosporidium parvum primarily infects calves, and clearly makes people (and calves) sick. However, because it is relatively common in people as well, in many cases it is hard to say if a person with C. parvum was infected by contact with calf stool or human sewage.
  • Both the dog-associated C. canis and cat-associated C. felis have been found in people, and C. felis can cause diarrhea even in immunocompetent individuals. Infection with these species in humans is very uncommon compared to C. hominis and C. parvum
  • The largest outbreak of cryptosporidiosis ever reported in North America occurred in Milwaukee in 1993, when an estimated 1.6 million people were exposed to the parasite and over 400 000 people became sick as a result of the infection.
  • In most studies, contact with pets is either not associated with the risk of cryptosporidiosis or may even have a slight protective effect. One study showed no significant association between pet ownership and cryptosporidiosis in HIV patients.
A scientific review of the transmission of Cryptosporidium (and Giardia, another common waterborne parasite) is available from the International Journal of Parasitology. For more information on Cryptosporidium in pets, check out the information sheets on the Worms & Germs Resources page.

The pinworm myth

Pinworms are small white worms that live in the rectum (the very last section of the large intestine). The human pinworm is called Enterobius vermicularis. Pinworm infections tend to be fairly mild (the sight of them is often more distressing than what they actually do), causing itching around the anus. Pinworms are common in young children and can be spread between people living in the same household. Pinworms are transmitted by swallowing pinworm eggs, which can survive in the environment for up to 2 weeks.  Handwashing after using the bathroom is a key way to reduce the risk of transmission.

A recurring myth is that pets are a source of pinworm infections in people. Pets cannot spread human pinworms, nor can they become infected by human pinworms.

If your child has pinworms, there are various measures that should be taken to reduce transmission and prevent recurrence. But testing, treating or banishing the household pet is not one of them!

Tapeworms in dogs and cats

Finding a tapeworm in a pet's stool can be a concerning event for some people. Tapeworms are  intestinal parasites that can be found in varying percentages of dogs and cats. A common tapeworm (at least in North America) in dogs and cats is called Dipylidium caninum, and it can be found in a high proportion of dogs and cats in some regions, particularly animals that go outside and are infested with fleas. There is minimal concern about transmission of this tapeworm to people. Taenia pisiformis (dogs) and Taenia taeniaeformis (cats) are also common, and neither of these can infect people.

People typically realize their pet has tapeworms when they see small tapeworm segments in the animal's stool. These whitish, rice-sized pieces (called proglottids, see the picture on the right) are parts of the adult tapeworm, which break off and are passed in the stool.

Tapeworms are not usually harmful to dogs and cats, particularly if only one or a few worms are present. In some situations, weight loss can occur. Affected animals may 'scoot' (drag their rear end across the ground) because of irritation from tapeworm segments that are passed in the stool.
Diagnosis of a tapeworm infestation is easiest through identification of tapeworm segments in stool. Identification of tapeworm eggs in stool samples through routine testing used for other intestinal parasites is less useful, as the bare eggs are infrequently shed in stool.  Therefore, a negative fecal egg examination does not rule out tapeworms.

Dipylidium infections are extremely rare in people. Children are at greatest risk. Disease in people, if present, is usually mild and easily treated. However, finding tapeworms in a person's stool can be distressing to the individual (and their family). Dipylidium cannot be transmitted directly from animals to people. People and pets get infected by ingesting a flea that is infected with tapeworm larvae. Therefore, flea control is the most important aspect of tapeworm prevention. People that find tapeworm segments in their stool should contact their physician to determine whether they are actually tapeworms (people often mistake other things for tapeworm segments) and to determine whether any treatment is needed.

There are specific dewormers that can be prescribed by your veterinarian to eliminate tapeworms in pets. It is also important to take measures to control fleas and prevent dogs and cats from catching and eating animals that might be carrying fleas.

Removing ticks

As we (finally) get nice weather here, a rash of questions about ticks usually follows.  Ticks are very common in some areas, and a short walk in the woods can result in exposure. Ticks themselves aren't the concern. The problem is infectious diseases that ticks can transmit, including Lyme disease. The risk and types of diseases of concern vary geographically. (In Ontario, exposure to ticks that can transmit Lyme disease is most common in Point Pelee, Rondeau, Long Point, Turkey Point and the Thousand Islands area). There are a number of ticks that may feed on people and pets, but only a few that transmit infections. Your veterinarian, physician and/or public health departments should be able to tell you what diseases are of concern in your area.

Regardless of where you live, if you and your pet might encounter ticks, you should know how to remove them. Prompt removal is the key. Most tickborne diseases aren't transmitted immediately. Rather, the tick must be attached for a period of time for infection to occur. Therefore, close inspection of your pet (and yourself) for ticks after spending time outside, is important.

The following tick removal tips come from the Centers for Disease Control and Prevention (CDC).
  • Remove a tick as soon as you see it.
  • Use fine-tipped tweezers to firmly grasp the tick very close to your skin. With a steady motion, pull the tick away from your skin. Then clean your skin with soap and warm water.
  • Avoid crushing the tick’s body.
  • Do not be alarmed if the tick’s mouthparts remain in the skin. Once the mouthparts are removed from the rest of the tick, it can no longer transmit Lyme disease bacteria.
  • If you accidentally crush the tick, clean your skin with soap and warm water or alcohol.
Tick removal devices are also available and can be used in place of tweezers. If you use one, make sure the device does not squeeze the tick's body as you remove it.

If a large number ticks are present on your pet, you should contact your veterinarian for assistance. Typically, a product that kills ticks will be applied to your pet.

There are various anecdotal recommendations that should be avoided, including burning the tick off with a match and covering the tick with substances such as gasoline, petroleum jelly or nail polish.

Dog stool and garbage

I received the following question yesterday:

For approximately 20 years I have been involved in waste collection for the Parks Division.  A considerable amount of the waste which I collect on a daily basis is dog excrement.  This is usually, but not always contained in a plastic bag and thrown into a large garbage barrel which I man-handle and dump in a waste truck. Years ago I contacted the local Health Unit and asked if there was any special health risks associated with this job.  They advised me at that time the main danger to health would be with E.coli contamination.  I use neoprene gloves while carrying out my duties and of course try to ensure that I do not come in contact with any debris. This is not always possible.

There are 3 main risks with handling dog stool: exposure to bacteria that cause diarrhea, exposure to intestinal parasites  and infection of wounds.

Various bacteria that can cause diarrhea can be present in dog stool. These include Salmonella and Campylobacter. E. coli is not a major concern because strains found in dogs are not typically those that cause disease in people. A few intestinal parasites are also of concern, including Giardia and roundworms. The risk of exposure to these is hard to say because you don't know anything about the health status of the dogs, but it's wise to treat all stool as infectious. However, for these to cause disease, they must go from the garbage and into your mouth. The risk of this should be minimal with basic common-sense precautions.

A large number of bacteria present in stool can cause infections of wounds like cuts and scratches, or other skin lesions such as eczema. Direct contact of these lesions with stool would be required to cause infection. The risks of this can also be greatly reduced with basic preventative measures.

Some basic precautions (many of which you are doing) include:
  • Wear gloves when handling bags containing stool.
  • Change your gloves if they become contaminated with stool.
  • Have your gloves cleaned periodically, and whenever they become contaminated. Otherwise, use disposable gloves.
  • Promptly wash or disinfect your hands if they become contaminated. Carrying an alcohol-based hand sanitizer in your truck would be useful.
  • Wear coveralls or some other sort of outerwear that can be removed easily if contaminated. If your clothing becomes contaminated, change it (and wash your hands after).
  • Wash your hands after removing your gloves (and especially before eating).

Overall, the risks to you should be very low.

Stray kittens

While visiting my parents this weekend, we came across a litter of stray kittens in the backyard. This is not an uncommon event and many people obtain their cats this way. Adopting stray kittens can be a great way to get a cat because it provides  a good home for kittens that would otherwise end up increasing the feral cat population. However, there are some things to consider to reduce the risks to your family and your other pets.

Various bacteria that can cause diarrhea in people can be carried by kittens, including Salmonella and Campylobacter. These are shed in the stool of infected animals, and people can become ill from handling the animal or stool-contaminated areas. Kittens may have higher rates of carriage of these bacteria than adult cats. Another bacterium that can be carried commonly by kittens is Bartonella henselae, the cause of cat scratch disease. This is transmitted by bites, scratches and fleas, and is just one reason for proper flea control.

Stray kittens are also more likely to carry Toxoplasma, a parasite that is a concern in pregnant women and immunocompromised individuals. Other intestinal parasites such a roundworms are also a concern. Kittens are more likely to have these parasites than adult cats.  Stool contamination of the haircoat is presumably more common in kittens as well because they are not as good about cleaning themselves as adult cats.  So just handling a kitten, even if you avoid its stool, may result in exposure to some of these parasites and bacteria.

Rabies is always a concern, and widespread exposure of people to rabies has occurred from infected litters of kittens.  While uncommon, rabies is a major concern because it is almost invariably fatal. Any stray (or recently rescued) animal that starts acting strangely should be considered a rabies-suspect and be taken to a vet immediately. [More information on rabies, and other topics, is available in our Resources page].

Stray kittens can also carry various infectious diseases that can be transmitted to other cats in the household, such as feline leukemia virus, panleukopenia, rhinotracheitis and calicivirus.

Overall, the risks from adopting stray kittens are low, but they are real. If you are going to adopt/rescue a stray kitten, keep these things in mind:
  • Take the kitten to your vet as soon as possible to identify any health issues and determine the required vaccination, deworming and flea control program
  • Wash your hands after handling the new kitten
  • Keep the new kitten in a confined area while litterbox training is underway to reduce accidents throughout the house
  • If you have another cat, make sure it is up-to-date on vaccinations before the kitten comes into the house.
  • If the kitten gets sick, make sure it is taken to a vet. If it dies suddenly, make sure you take it to your vet to determine whether testing for rabies is required.
  • Pregnant women and households with immunocompromised individuals should not adopt stray kittens.

Camping with canines - tick tick not!

The warm weather is just about here, and that means the start of camping season. Lots of people love to spend time in the great outdoors during the summer, whether it’s at a summer cottage on the lake, trailer camping in a park with electricity and running water, or roughing it in a tent in the peace and solitude of a more remote wooded location. And many people bring along their faithful companions – their dogs – who enjoy the experience just as much, if not more, than we do.

But there are also dangers lurking in the forests – microscopic dangers carried by tiny insects and other bugs. Ticks in particular are problematic. Certain ticks can carry a number of diseases that can make dogs sick, including Lyme disease (caused by Borrelia burgdorferi) and Rocky Mountain Spotted Fever (RMSF)(caused by Rickettsia rickettsii ). Both Lyme disease and RMSF are more common in certain areas where the tick species that carry them are present.  You can NOT catch these diseases from your dog, but both you and your dog can be infected by the ticks that carry them. People can also be exposed to these pathogens by accidentally crushing an infected tick while trying to remove it from their dog. Ticks must be removed very carefully to ensure that the entire tick is removed, including the head and mouth pieces, without crushing it. If you're not sure how, contact your veterinarian.  Also, the sooner the tick is removed, the less likely it is to transmit certain diseases, so be sure to check your dog thoroughly for ticks when you come back from a walk in the bush.

The Minnesota Department of Health recently reported that the number of cases of (human) Lyme disease increased in that state in 2007. This could be because of spreading tick populations, more people participating in activities in tick-inhabited areas, or increasing awareness and diagnosis of the disease by physicians.

If you and your canine companion will be spending time in some of the wilder and woodier parts of the great outdoors, talk to your veterinarian about what you can do to protect your dog. There are vaccines available for Lyme disease and the bacterial infection leptospirosis (which is also transmissible to people). Flea and tick preventatives are also very important, and many of today’s products are very effective. People should always wear insect repellent when camping or hiking in the woods. Visit the Health Canada website for safety tips on using personal insect repellents. All dogs should be vaccinated for rabies, whether they go camping in the backwoods or they’re house-bound city-slickers.

Sandbox fun...

A sure sign that spring is approach is the advertising of outdoor summer items in stores. A large pile of sandboxes at one store caught my eye the other day, particularly as it followed a discussion I had with some infectious disease physicians about kids and sandboxes. Sandboxes can be a great thing for kids, however there are some infectious disease concerns. Uncovered sandboxes can become litter boxes for cats, raccoons and other outdoor animals. Some of these animals could be passing potentially dangerous bacteria and parasites in their stool. An example of this was reported a few months ago in Morbidity and Mortality Weekly Report. This report described an outbreak of cutaneous larval migrans in 18 children and 4 staff at a day camp. This is a skin disease caused by hookworms. Cats and other animals can pass hookworm eggs in their stool. A sandbox contaminated with cat stool was implicated as the cause.

We really have no clue about how common sandbox exposure causes disease. While this skin disease is usually relatively minor, there are some other groups of parasites that can migrate through other parts of the body, including the brain, and cause devastating illness. All of these are very rare in northern climates like Canada, but measures should be taken to reduce the risk of exposure because of the potential severity of disease. Risks are much higher in warmer climates. These are a significant concern in warmer areas. It’s probably pretty uncommon but some of the diseases that can occur are very serious, so attention should be paid to these risks. The main things that can be done to reduce the risk are keeping animals out of sandboxes and handwashing after contact with sand. Check out our “Sandbox” information sheet for more details.

Information Sheets for Pet Owners

INFORMATION SHEETS specifically for KIDS, for VETERINARIANS, for PHYSICIANS and for PUBLIC HEALTH PERSONNEL are also available on the Worms & Germs RESOURCES page!

Click on the highlighted topics below for information sheets. Topics that are not highlighted are in development and coming soon. Sheets for other animal species and diseases are also under development and will be added when they are available.

Diseases Other
Dogs Rabies Litter Boxes
Cats Giardia Sandboxes
Turtles Toxoplasma Cat Bites
Hamsters Leptospira Raw Meat
Rabbits Clostridium difficile Petting Zoos
Pet Birds Cryptosporidium Needlestick Injuries
African Dwarf Frogs MRSA  
Reptiles MRSP  
  MRSP (Deutsch)  
  MRSP (Francais)  
  Rat Bite Fever  
  Cat Scratch Disease  
  Lyme Disease & Ticks  


Please Remember:

  • Your veterinarian and physician are your ultimate resource for information about the health of your pets or your family.
  • Information provided here is accurate to the best of our knowledge, but infectious diseases can be unpredictable and these sheets are for general information purposes only.
  • There can be great variation in disease risks in different geographic areas. The information provided was developed for Ontario, Canada, but most of the information is relevant for other regions as well.

Equine Infectious Disease Information Sheets

Click on any of the highlighted links below for more information about these horse-related infectious disease topics. Topics that are not highlighted are in development and coming soon. New information will be added as it becomes available, so be sure to check this page regularly for the latest updates.

Bacteria Viruses Parasites Other
Clostridium difficile Rabies Bots Pleuropneumonia
Clostridial Myonecrosis Eastern Equine Encephalitis Equine Protozoal Myeloencephalitis (EPM) Neonatal Diarrhea
Strangles (Streptococcus equi) Equine Herpesvirus Cyathostomes
(Small Strongyles)
Needlestick Injuries
Methicillin-resistant Staph aureus (MRSA) Equine Influenza Large Strongyles Colostrum
Lawsonia West Nile Virus Tapeworms  
Rhodococcus equi Equine Infectious Anemia - Summary Pinworms  
Tetanus Equine Infectious Anemia - Full-length    
Botulism -
Botulism -
"Shaker Foals"

All information sheets found on this page can be freely downloaded, printed and distributed. The authors only request that this website (, previously is acknowledged as the source.  The downloadable files on this page can be opened with Adobe® Reader®.  To get the latest version of Adobe® Reader® for free, click here.

Research Posters

2012 International Clostridium difficile Symposium

2012 International Conference on Equine Infectious Diseases IX

2011 ASM-ESCMID Conference on Methicillin-resistant staphylococci in animals

2011 University of Guelph Centre for Public Health and Zoonoses Symposium

2011 Canadian Animal Health Laboratorians Conference

2011 Canadian Association of Clinical Microbiology and Infectious Diseases

Coming soon

  • 2011 American College of Veterinary Internal Medicine Forum, June
  • 2011 ASM-ESCMID conference on methicillin-resistant staphylococci in animals, Sept