Worms & Germs Blog

Echinococcus multilocularis back in the news

Posted in Deworming, Dogs, Parasites

Nothing has changed about Echinococcus multilocularis (the fox tapeworm) in the past couple of months, but my phone is ringing off the hook following another round of media reports about this parasite. Here’s a recap of the issues:

  • Echinococcus multilocularis is a small tapeworm normally found in the intestinal tract of wild canids (e.g. coyotes, foxes) and sometimes dogs. For these animals, having this worm in the gut doesn’t cause a problem. The main concern is when something (or someone) ingests tapeworm eggs that are passed in feces of these canids.  This can result in a condition called alveolar echinococcosis (AE), in which tumour-like parasitic cysts can develop in other parts of the body, particularly in the liver.
  • In the normal (wildlife) life cycle of this tapeworm, wild canids shed eggs in their feces which are eaten by small rodents, that then develop AE. When a canid eats an infected rodent, the parasite grows into its adult stage in the canid’s gut and produces more eggs, and the cycle continues.  While that’s bad for the rodents, the bigger problem is that this “intermediate host” stage can occur in more than rodents… including dogs and people.
  • Alveolar echinococcosis has been diagnosed in a small number of Ontario dogs (with little to no travel history) since 2012, raising questions about how they got infected. The concern was that this parasite had become established in our wild canid population, which presents an ongoing risk to people and other animals, and is very hard to control.
  • Human cases in Canada are rare but are being found and may be underdiagnosed.  Since AE is a very nasty disease, and very difficult to treat, we’re inherently cautious.

The recent news stories picked up on a study published earlier this year in Emerging Infectious Diseases (Kotwa et al 2019), where an astounding 23% of wild canids in Southern Ontario were found to be shedding Echinococcus multilocularis. 

What’s the risk to dogs in Ontario?

  • We don’t know. I realize that’s not comforting but it’s the honest answer. We should know a lot more in the next few months as we test samples from pet dogs in the highest risk areas. Until then, it’s hard to say much with confidence.

What should dog owners do?

There are two main approaches to prevention: decreasing the risk of exposure and prophylactic treatment.

We can treat dogs for tapeworms, but this isn’t usually part of routine deworming protocols, so only a small percentage of dogs are treated on a regular basis. I’ve been treating my dog with praziquantel monthly for the past couple of years, since emergence of the parasite was identified, because we’re in a higher risk area and he will eat anything. We live in the country and have a lot of coyotes around. If the parasite is here, it’s quite plausible he would be exposed.

The risk is much lower (or non-existent, potentially) in other regions, and dogs that have less outdoor access are much lower risk. Quantifying that risk is the challenge.

Ultimately, whether or not to treat a dog prophylactically is a case-by-case decision, based on the dog’s risk factors (and the owner’s risk aversion).

More information about Echinococcus multilocularis can be found on the Worms & Germs Resources – Pets page. Also check out emultiontario.com and the updated infographic from the Ontario Animal Health Network.  We’ll provide updates as more information about this parasite becomes available.

Linezolid resistance in dogs and cats

Posted in Cats, Dogs

A recent presentation at ECCMID (European Congress of Clinical Microbiology and Infectious Diseases) in Amsterdam described a series of linezolid-resistant enterococci in dogs and cats in the UK. I’m only able to get information from media reports, so details are limited (and potentially lost in translation); however, it’s an interesting story. It’s unsurprising in many ways, but highlights some important issues.

Linezolid is an antibiotic that’s typically used in human medicine for infections caused by multidrug-resistant Gram-positive bacteria such as staphylococci (including MRSA) and enterococci. It’s rarely used in veterinary medicine, but has been used in dogs and cats for the same types of infections. Because it’s one of few options for treatment of MRSA in people, it’s an important drug, and resistance is a significant concern.

The UK story involves a cluster of infections at one veterinary clinic. Enterococci that were resistant to linezolid were found in two cats and one dog. They were found to carry a gene, optrA, that confers linezolid resistance.  This is the first time this gene has been found in a bacterium from a companion animal in the UK. optrA is found on a plasmid, a small piece of DNA that can be move relatively easily between bacteria, meaning it can potentially spread to other bacteria of the same species, or even to those of other bacterial species. There are no details in the reports I’ve seen about timing of the infections, and whether the cluster in the clinic was likely due to direct contact between animals, contact with a contaminated environment or contact with people who were either contaminated (e.g. carrying the bug on their hands from touching an infected animal or contaminated surface in the clinic) or colonized (i.e. people who harbour the bacterium in their intestines and can be a source of contamination themselves).

Where did the linezolid-resistant enterococci originate?

It’s hard to say from the limited information I’ve seen. It could have come from a person, as there are lots of instances of humans infecting their pets with a variety of bacteria. That’s largely how MRSA originates in dogs and cats, and other resistant bacteria that are common in humans have entered the pet population in this way.

Use of linezolid in animals should not have played a role. Articles have stated that linezolid is not used in dogs and cats in the UK, and while I question whether that’s actually true, linezolid use is so rare to non-existent in pets that there’s probably no realistic risk of emergence of resistance from use of that drug in these species. However, optrA doesn’t just confer resistance to linezolid. It also confers resistance to chloramphenicol and florfenicol, drugs that are (uncommonly) used in dogs and cats. This highlights the “co-selection” issue, when the use of one drug can select for resistance in other drugs. I suspect a human source is more likely here but it’s hard to say.

According to one article, the authors indicatedOur findings further the ‘One-Health’ view that antibiotic-resistant bacteria can be shared by animals and humans, although the direction of transfer is often difficult to prove. We currently do not know the prevalence of linezolid-resistant enterococci in companion animals and therefore a joint approach to monitoring emergence and dissemination of resistance mechanisms of public health importance is needed”, says Dr. Hopkins. “In this instance, further transmission was stopped by cleaning and decontamination and we have no evidence that any people acquired an infection from these animals.”

What this means in the big picture is hard to say, but it shows how resistant bacteria and resistance genes can move between and within species, sometimes in unexpected ways. It also shows how the common bug-drug-species focus (i.e. looking at one type of resistant bacterium in just one (human or animal) species) can miss the big picture. Antimicrobial resistance is a complex ecological problem that requires a complex and comprehensive approach, which is currently still lacking.

PetsAndTicks… New for 2019

Posted in Cats, Dogs, Parasites

I keep saying spring is approaching and I keep getting disappointed by the cold weather.  But it’s going to happen soon, so we’ve been gearing up for tick season. There are a few new initiatives underway for tracking ticks and tickborne diseases in Canadian dogs and cats. Check out the recent post at PetsAndTicks.com for more information.

Confusing Lone Star tick advertising

Posted in Cats, Dogs

The snowfall we had on the weekend notwithstanding, spring is here. As the weather warms up in Ontario (and other regions), we have to once again think more about ticks. Once the temperature reaches ~4C, hungry ticks that didn’t feed in the fall will come out, looking for food. Accordingly, tick prevention for people and pets needs to be considered.

The return of ticks also means the return of pet tick preventative advertising, and that’s leading to confusion and questions. The “Lone Star Louie” ads, in particular, are leading to a rash (pardon the pun) of emails. They focus on the Lone Star tick (Amblyomma americanum), but also include some confusing, mixed and misleading messaging, talking about this tick in dogs, red meat allergy and Lyme disease.

First, the concern about the A. americanum

The Lone Star tick is an aggressive tick that can spread a few different diseases. We’re paying more attention to it in Ontario now because we expect it to become a problem over time. We see small numbers every year, and so far we’ve assumed that these are ticks have been carried north by migrating birds. Established populations (i.e. finding all life stages of the tick at a particular location, typically over at least a two year period) have not been recognized in the province (yet). However, we’re on the look out for it through initiatives such as our Pet Tick Tracker.

Next… questions about the advertising

Red meat allergy

  • This is a really interesting story but one that has no relevance to dogs and cats. Lone Star tick bites can result in an acquired red meat allergy in people. It’s uncommon, but bites from this tick can result in sensitization of peoples’ immune systems to a protein that’s found in red meat. People can get sensitized to it because it’s not a component of their bodies. In contrast, dogs and cats are made of that protein, so they can’t develop the same kind of red meat allergy (i.e. an allergy to themselves). So, while it’s a concern with this tick, it’s of no relevance to dogs and cats, and dogs and cats do not lead to people being exposed to the tick or developing the meat allergy.

Lyme disease

  • Lyme disease gets mentioned in the ad too, but this tick does not harbour the bacterium that causes Lyme disease (Borrelia burgdorferi).  That particular pathogen is most often carried by black-legged ticks (e.g. Ixodes scapularis).

So, the Lone Star tick is a concern (albeit still a minimal one in Ontario). However, red meat allergy messaging is irrelevant to marketing tick preventives for dogs and cats, and Lyme disease is not a risk from this tick. Tick prevention is important in dogs (and to a lesser degree cats) and the use of tick preventative medicine is an easy and effective way of reducing the risks associated with ticks. The messaging needs to be better, though, to avoid confusion and misinformation.

High pressure pasteurization of raw pet food diets

Posted in Cats, Dogs

Raw diets have been in the news a lot lately because of Salmonella contamination. It’s not surprising at all since bacteria like Salmonella, E. coli, Campylobacter and Listeria are expected to be found in raw meat (that’s why we cook it). We know that dogs and cats fed raw meat are at increased risk of shedding bacteria like Salmonella, sometimes with serious consequences to the animals or their owners.

Reducing the risk is a challenge when you know there’s a reasonable chance the food is contaminated, and when the preferred method of control (cooking) isn’t used. Irradiation is an alternative approach, but not something in which a lot of raw feeders are probably interested. High pressure pasteurization (HPP) is therefore increasingly being used to help control bacterial contamination of these products. HPP, as the name suggests, uses high pressure (with minimal increases in temperature) to reduce bacterial loads.

Notice I said reduce, not eliminate.  That’s the problem.

A while ago, I used to go on the assumption that raw food products that underwent HPP were similar in risk to commercial cooked diets, with the disclaimer that we don’t really know for sure. We still don’t know a lot, but what we know now isn’t encouraging, so I’ve had to change that assumption.

I’ve talked to a few people who have done limited investigations of foods treated with HPP, and the results were disappointing. Unfortunately the studies were small and remain unpublished.

A 2016 research abstract gives us a bit more substance (although a proper research paper would be preferred). In that study (Hasty et al. 2016, Reciprocal Meat Conference – Meat and Poultry Safety), raw beef pet food was spiked with E. coli. (A harmless strain of E coli was used in place of a disease-causing strain or other bacteria like Salmonella, presumably because of biosafety concerns.) They used a HPP process that subjected the meat to a standard pressure (600 mpa) for 480 seconds. Then they checked to see if any viable bacteria were left in the meat.

The good news: There was a definite reduction in viable bacteria.

The bad news: It didn’t kill them all.

This doesn’t mean HPP is ineffective. It’s a matter of being aware of what it can do, and what it can’t. It can reduce the number of viable bacteria in the food, and that probably reduces the risk of disease in people and pets. But it does not eliminate all the bacteria, so it can’t eliminate the risk (only proper cooking and handling will do that).

If someone is going to feed a raw diet, I’d still recommend using a HPP-treated diet versus one that has bot been treated. However, people have to realize it’s not a panacea and that they still have to assume the food is contaminated.

Here’s a quick reminder of some basic take-home messages for raw meat feeding:

  • There’s always some risk of bacterial contamination. We can reduce, but not eliminate, that risk.
  • Careful handling is required to prevent cross-contamination of human foods, surfaces and environments. A little common sense when it comes to food handling can go a long way (but it’s amazing how uncommon “common sense” can be… check out Barfblog.com for annals of food safety stupidity).
  • Raw meat diets should not be fed to dogs and cats at increased risk of serious disease (e.g. very young, elderly, pregnant, immunocompromised) or in households where people (or pets) fitting those categories are present.
  • People who feed raw diets should make sure their veterinarian knows this, should their pet get sick. The same applies on the other side of the One Health spectrum – if someone is feeding raw meat to their pet and a person in the household has gastrointestinal disease, exposure to raw meat needs to be mentioned to the physician involved.

More information about raw meat feeding and basic safety practices is available on the Worms & Germs Resources – Pets page.

Canine brucellosis: US

Posted in Dogs

I guess we’re not the only ones dealing with Brucella canis issues lately. In February, we were dealing with B. canis in dogs imported into Ontario from South Korea. Currently, we’re dealing with a larger issue in commercial dog breeding facilities in Ontario.

Imported Brucella canis also appears to be an issue in the US at the moment.  Two dogs from South Korea that went to Wisconsin were recently diagnosed with brucellosis. They originated from a larger shipment of dogs from South Korea, and I have to wonder whether they’re from the same batch that came to Canada in February in which we found infected dogs (maybe they were even tested in response to what we found). Regardless, the imported dogs and the dogs that were exposed to them (a total of ~100 dogs) are under quarantine at the moment. Owners of dogs from the exposed group that have already been adopted are being contacted by state public health officers to instruct them to quarantine (and presumably test) the dogs.

The article was picked up by ProMedMail, with the following moderator comments:

“The lax import regulations of rescue animals coming into the USA is on the verge of a serious problem. The USA has quarantine facilities at ports for cattle, horses and other livestock. It needs to be expanded to include dogs and likely other animals. Imported rescue dogs especially need to have their vaccinations for prevention of rabies, distemper, parvo virus and other diseases. While being held at a facility, they should be checked for other diseases such as canine influenza and zoonotic diseases such as brucellosis.

Rescue animals from other countries need to be quarantined, not put in foster homes where there could be exposure to other animals or immunosuppressed individuals until some of these vaccines and testing have been performed. These quarantine facilities should be inspected by knowledgeable individuals according to law.”

Great in theory but it’s never going to happen. All we can realistically do is educate to improve importation practices to reduce the risks, but the risk will never be eliminated completely so long as dogs are crossing the border.

Rabies vaccine failure in a dog?

Posted in Dogs, Rabies, Vaccination

Rabies vaccination of dogs is legally required in many areas. In most of those, it must be given by a veterinarian, unlike some other vaccines that can be purchased from a veterinarian or supplier and administered by owners.

Why does a veterinarian have to administer rabies vaccines? There are a few reasons.

  • One is that it helps ensure that the vaccine is handled properly. In a vet clinic, where vaccine handling and storage is routine, there’s less chance of the vaccine being handled inappropriately (e.g. left out of the fridge for a prolonged time). Poor handling, especially failing to maintain “cold chain” (keeping the vaccine cool at all times until it’s administered) is a particular concern in other situations.
  • Having a vet administer the vaccine also decreases the risk of problems caused by inappropriate administration (e.g. not getting the full dose into the animal).
  • There can also be a greater assurance that if a vet signs a rabies certificate, that the animal was actually vaccinated, as opposed to if a person just says they vaccinated their own dog. Veterinary records are also presumably better at recording when the vaccine was given, what vaccine was given and the lot number, all things that can be relevant.

A recent case in Texas highlights this issue. A dog in El Paso County was diagnosed with rabies, and while the news article isn’t particularly detailed, it’s stated that the owner gave the dog a rabies vaccine. The health department was unable to confirm where the vaccine came from or who gave it (and I assume we have to wonder whether it was actually vaccinated… maybe they just said it was, or maybe they vaccinated the dog against something else and only thought they’d vaccinated it for rabies).

Rabies vaccine is a highly effective vaccine, so I doubt the dog was vaccinated properly (and currently) vaccinated given that it developed rabies. If it was, I wonder if it was a very poorly handled vaccine or a cheap vaccine purchased from a questionable source, versus a mainstream veterinary vaccine. Vaccine failure from a properly administered, adequate quality vaccine is exceptionally unlikely.

While rabies in dogs and cats is quite rare in Canada and the US (and most countries that don’t have endemic canine rabies variant circulating in the feral dog population), it’s an almost invariably fatal disease, so we take it very seriously. Vaccination of pets is important to protect pets and the public, and the cost of a vet administering the vaccine is a lot less than the cost, hassles and risk from inadequate vaccination resulting in exposed animals getting infected.

Canine leptospirosis maps

Posted in Dogs, Other diseases, Vaccination

I’ve had a few discussions with people over the past week about geographic variation in disease risk. It’s a great subject because it’s an important and often overlooked issue. Whether it’s animals being imported, animals moving with their owners, animals accompanying owners on vacation or animals being moved between regions within the county, movement between regions can involve picking up or moving diseases at the same time.

From a veterinary standpoint, the challenge is identifying issues that you wouldn’t normally consider, because the disease is rare or non-existent in your practice area. The first step is querying travel history (which is done variably well). The next is figuring out what that means. We don’t have great resources that say “if you go here with your dog, this is what you need to be concerned about.” I get questions about travel risks all the time, and it’s taken a lot of effort to get up to speed with risks in different regions (and I still have a lot of gaps). We’ve published the odd (crude) map to help out, but getting good quality information, ideally based on surveillance data, and assimilating it into a central resource is a more significant challenge than one might think (a goal of ours, for sure, but a slow process given time and money limitations).

Regardless, we’re getting more information all the time and getting that out in the open is important. Dr. Michelle Evason wrote a post on her K9 Lifetime Study blog about the leptospirosis data we’re working on, and I thought that was worth putting up here too. It’s a fairly high level map of a few years of leptospirosis cases in dogs in Canada, based on data from IDEXX Laboratories. There are limitations with any dataset of this kind, so it’s not a perfect representation of this disease. However, it still provides some useful information. Lepto is a nasty disease and also a vaccine-preventable disease. So, understanding where it’s common is important for thinking about it when you have a sick dog (i.e. making a diagnosis) and discussing vaccination programs.

The incidence is adjusted for human population, on the assumption that dog ownership trends are similar across the country. We do that so that we don’t see bias towards big cities. If we just plot the number of cases,  places with a big dog population but low incidence of disease could have more cases than a true high risk area with a lower population, thus hiding the real risk.

This bacterium lives in different wildlife hosts (e.g. raccoons, rodents), is passed in their urine, and survives well in moist, temperate climates. Unsurprisingly, we see lepto concentrated in much of Ontario and east of here, particularly in southern regions, as well as coastal British Columbia. Risks vary within those regions too, and lepto vaccination discussions require some assessment of other risk factors as well (although I consider lepto vaccination a core vaccine in most of the green (and all of the blue) regions on this map).

Polar bears and Clostridium difficile

Posted in Other animals

And now for something completely different.

We’ve studied Clostridium difficile in my lab for years and we probably have one of the world’s most diverse collections of this important bacterium. We have thousands of isolates from people, pets, livestock and many different wildlife species (as well as from meat, vegetables and water).  Most of the focus on C. difficile involves human disease, which makes sense because it’s a very important cause of serious gastrointestinal illness in people. It causes disease in some animal species, but in many, it doesn’t seem to ever cause a problem.

Looking at the genetic makeup of a bacterium, it’s possible to infer how old it is. C. difficile is pretty ancient. It’s been estimated that in emerged 1.5-85 million years ago (He et al. PNAS 2010).  That’s well before humans (or potentially even mammals) emerged, so it’s clearly not a human-origin bacterium. Rather, it evolved in wildlife and certain strains have made their way into people.

That’s a long introduction for a paper we just published about C. difficile in polar bears (Weese et al. Anaerobe 2019).

Why polar bears?

Usually, we do “hypothesis driven research,” where we come up with a specific answerable question or problem and try to answer or solve it (or some small part of it).

Sometimes, we’re opportunistic and curious, with less of a real plan. Here, it was basically someone saying “we have polar bear poop… is there anything you’d like to do with it?” Sometimes these curiosity-driven studies are quite rewarding.


We got samples from a large study that was collecting feces from wild polar bears in the Canadian Arctic, bears temporarily housed in the Polar Bear Jail in Churchill, Manitoba (a facility to where nuisance bears get shipped for a while before being released back into the wild), and a few polar bears from a zoo.

Surprisingly, we found C. difficile in almost 17% of samples: 18/120 (15%) from wild bears, 4/7 (57%) from the polar bear jail and 2/16 (13%) from the zoo.

To be honest, my first thought when we had so many positive results was “crap, contamination” (pardon the pun). However, typing of the bacterium showed us this was not the case. We found a variety of C. diff strains, but none of the strains in the in the wild bears were the same as strains we’ve ever seen. Also, the strain distribution was different in bears from the M’Clintock Channel compared to those from Hudson Strait (two different bear populations), despite the fact that the samples were all processed together in the lab. (So it couldn’t have been contamination at the lab level – that made me feel a lot better.)

Were the polar bears sick?

It’s hard to say, but probably not. Fecal samples were collected off the ice or ground, not right from the bear (for pretty obvious reasons). Presumably, like most wildlife species, C. difficile can be present in the gut of polar bears without causing disease.

How do polar bears get this bacterium?

We’ve been able to find C. difficile in most species that we’ve studied.  That includes most livestock species, pet species and a range of wildlife, from raccoons to bats. It’s also been found in seals (not in the Arctic, but I’m not aware of anyone looking there). Since seals are a common food source for polar bears, if the bacterium is present in seals in the Arctic, that’s a likely source of exposure.

Does C. difficile-shedding in polar bears pose a risk to people?

I guess. However, there are lots of ways that we can get exposed to this bacterium. It’s possible we get exposed to low levels of it most days. If you’re close enough to the polar bear to get C. difficile from it, you probably have bigger things to worry about.