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.
I’ll admit it - I don’t understand dogs. How is it that they have this incredibly well-developed sense of smell, but my dog feels it necessary to roll in the most disgusting smelling things he can find? I guess it’s not that he feels like he needs strong body odour, just that he has a poorly developed part of the brain that says “hey, that smells gross” (along with related parts of the brain that say “hey, that tastes gross,” “maybe I shouldn’t chase that skunk,” and “maybe body slamming the side of the bed to scratch my back at 4 AM doesn’t endear me to the people that feed me.”).
Anyway, that’s a pretty indirect introduction to a question of what animals can track back into the household and other unusual routes of zoonotic disease exposure. I won’t get into the whole issue, but I have had a rash of calls lately from people worried about indirect exposure to rabies virus. Questions have include:
- My dog was nosing raccoon roadkill. What if the raccoon had rabies?
- If I run over an animal and then touch the tire, could contract rabies?
- If someone who works removing bats from houses comes over, could they have rabies virus on their shoes and contaminate my house?
For someone to get rabies, the virus has to go from the infected animal’s body (saliva or nervous tissue) into the person’s body. Rabies virus isn’t airborne, it doesn’t survive long in the environment and it can’t infect through intact skin. Indirect transmission of rabies is exceedingly rare, with one of the only examples that comes to mind being rabies in a family of shepherds who cared for a sheep that was attacked by a rabid wolf. The attack occurred right before the people handled the sheep, and wolf saliva (containing rabies virus) was likely present on the sheep’s coat from the attack, and the handlers had cuts on their hands. Very rare.
That said, with infectious diseases we rarely say "never." That often causes angst because people want to hear “there’s absolutely, positively no way you could have gotten [insert disease here] from [insert event here].” Yet, there are situations that are so unlikely that we probably should take the plunge and just say "never."
For example, is there a theoretical chance that an animal run over by a car would be rabid, and that brain tissue would be splattered on the tire, and that it wouldn’t be killed right away by heat from the tire, and someone would touch the tire right after and that person touched a virus contaminated area of the tire and the virus had contact with an open wound?
Sure, I guess...
However, while rabies post-exposure treatment is very safe, the odds of an adverse effect of post-exposure treatment are probably infinitely higher than the odds of getting rabies in weird situations like those about which we are sometimes asked. Considering how well rabies cases are tracking in developed countries, and how many wild animals have rabies, if indirect exposure was a real concern, we’d know about.
A recent report about a rabid raccoon in New Brunswick highlights a few different issues regarding rabies exposure, and the marked differences in application and interpretation of various guidelines.
The incident occurred in St. Stephen, New Brunswick, where a family came home "to find their 2 dogs excitedly circling around something in the yard. The object of attention was a raccoon, which evidently was moving abnormally slowly and was circling. The raccoon was killed and buried. Afterward, the dogs shared popsicles with the family's 2 young children. It was not known if the dogs had had contact with the raccoon, but if they had been bitten, it is likely that they would have licked any wounds they incurred and so could have been exposed to the raccoon's saliva. The raccoon was dug up and its brain was extracted by the New Brunswick Provincial Veterinary Laboratory and sent to the Canadian Food Inspection Agency Rabies Laboratory in Ottawa for testing. Test results were completed on [2 Jun 2014] and variant typing was completed on [3 Jun 2014]."
I’m a little surprised the CFIA tested the raccoon. Often (usually), it’s difficult to get testing done without clear evidence of exposure of either a person or a domestic animal. Here, it doesn’t sound like there was much evidence that the dogs had been exposed. I’m not saying don’t test - I think over-testing is better than under-testing, as long as results are interpreted properly.
"Post-exposure treatment has been started on the 2 children. Both dogs had been vaccinated previously against rabies, although one dog was overdue for revaccination. Both dogs were given booster vaccinations for rabies and have been put under quarantine. The family also has an indoor-outdoor cat which had never been vaccinated against rabies. The cat was vaccinated and also is being quarantined."
It seems like a big stretch to call this exposure of the kids. If the dog bit the raccoon, it’s very unlikely there would be rabies virus in the dog’s mouth, although it’s possible if the dog and raccoon swapped saliva during the process. However, rabies virus would then have to survive in the dog’s mouth, contaminate the ice cream, survive on the ice cream surface and make its way into the kids through the ice cream. To say that’s unlikely is very much an understatement. Again, I’d rather see erring on the side of caution when it comes to rabies, but unless there’s more to the story, this seems pretty extreme.
Considering the indoor-outdoor cat exposed seems even stranger, since there’s no information reported here that the cat was involved in the raccoon incident at all. Since exposure of an unvaccinated animal means a 6 month strict quarantine, that’s a very drastic measure for a situation like this.
Maybe something’s not being reported, but it seems a bit weird to me.
Some general take home messages:
- Stay away from wildlife.
- Think about rabies when there are encounters with wildlife, especially wild animals that are acting strangely.
- Vaccinate your pets (even the indoor ones!)
It's also worth noting that this was the first rabies-positive raccoon found in New Brunswick since 2002.
There’s been some controversy in the past regarding allowing pets to sleep in or on the bed. I don’t get too worked up about it, since I think it’s very low-risk in terms of disease transmission for most pets and households, but a variety if reasons for prohibiting this practice have been given.
I haven’t previously heard the reason: “Don’t do it because you might think you’re petting your cat when you are actually mistakenly pissing off the rabid raccoon that’s dozing beside you.”
Maybe that should be added to at list.
A Massachusetts woman learned this one the hard way. The woman was asleep one night a few weeks ago and reached over to pet what she thought was her cat. Unbeknownst to her, the critter beside her was actually a rabid raccoon that had come into the house through a cat door. Unhappy at being disturbed (and with a less-than-functional brain from rabies), the raccoon attacked, jumping on the woman's face and biting her lip, refusing to let go. She managed to pry the creature off her face, whack it with her phone and call 911. Animal control caught the raccoon, which was subsequently euthanized and confirmed as rabid.
From a more serious standpoint, this case highlights one of the big drawbacks of having a cat door that allows entry and exit of any cat-sized animal. Keeping cats indoors is a good idea for the cat’s health, the family’s health and the wild bird population (and avoids the cat door issue entirely!).
An article by Dr. Ann Britton of British Columbia’s Animal Health Centre (AHC) on the blog site healthywildlife.ca 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.
This time of year, it's very common around here to see young raccoons wandering about. It's also still pretty common to hear about people keeping a litter of baby raccoons in their house. I can understand the appeal - they're cute and entertaining. However, in addition to being illegal in many regions, handling young raccoons also poses a risk of exposure to a variety of infectious diseases.
Chief among the infectious disease risks of handling young raccoons is rabies, as a Walker County, Alabama, family found out. Two baby racoons were found in someone's attic, and another two littermates were found a little while later. The person who found them gave two each to two separate people. As is often the case, they were handled by many different individuals before one of the raccoon kits was found to be rabid. Now more than 20 people are facing post-exposure treatment. It's one of the larger reported exposures from a single rabid raccoon, but it's far from unprecedented.
Beyond the obvious public health concern, this situation demonstrates another possible issue. Rabies is sporadically distributed in some regions, and moving wild animals around leads to the potential for dissemination of rabies, as well as other infectious diseases. Raccoon rabies is present in the area where the baby raccoons were found, but has not been found in Walker County, even though it's not far away. If the rabid raccoon had escaped (or was released), it could have potentially spread rabies into an area where it's currently not well established, thereby increasing the risk of exposure to everyone (animals and people) in the county.
As mentioned above, it's also illegal to harbour wildlife in many regions if you are not a licensed rehabilitation facility. While getting fined seems to be uncommon, four people in this incident have been charged with unlawful possession of a protected animal. Just one more reason not to do this.
While baby raccoons may have some appeal, as Alabama's state veterinarian Dee Jones says, "...people just need to stay away from them."
There have been various news reports from different parts of North America describing distemper outbreak in raccoons. Distemper is a viral infection caused by canine distemper virus, which is related to the human measles virus (but the canine version can't infect people). A variety of animal species in addition to dogs can get distemper, most notably raccoons.
Distemper outbreaks are not uncommon in raccoons, and one big problem with distemper is that the neurological signs cannot be distinguished from rabies. Yes, there may be some general trends in how a raccoon with distemper behaves that differ from one with rabies, but it’s far from definitive. That creates issues because distemper is of absolutely no human health concern while rabies can be transmitted to humans and is almost invariably fatal.
A Windsor-Essex (Ontario) outbreak of distemper in raccoons highlights some of these issues and the care that must be taken with regard to public communications.
Authorities are “urging the Windsor-Essex public not to worry about a rising number of incidents with strange-acting raccoons: The poor scavengers are suffering from distemper, not rabies.”
- This is bad communication in my opinion. I’d rather see something like authorities are "urging the public the avoid raccoons because of the risk of rabies exposure, but to be aware that a raccoon that is behaving abnormally probably has distemper, not rabies." Telling people not to worry is okay, but making it seem like there's no issue whatsoever is another. No one can say for sure that all of these affected raccoons have distemper, not rabies.
A good statement appears later in the article ”(Executive Director of the Windsor-Essex County Humane Society Melanie) Coulter stressed that although the disease is highly contagious among animals, it can't be passed to humans. But she added that raccoons with distemper are still capable of sudden aggression, especially if they feel cornered. As well, the symptoms of distemper are similar to those associated with rabies -- and the difference can't be determined without lab testing.”
- That’s much better. It highlights the problem and explains that it’s probably not a risk to people, but also makes it clear that you can’t be sure it’s not rabies.
The key thing is avoiding contact with raccoons all of the time, with particular attention to raccoons that are acting abnormally, since they are more likely to have rabies and they can be unpredictable. Some other things to consider:
- Don’t keep raccoons as pets (common but illegal, at least here).
- Don’t encourage raccoons to live around your home.
- Keep pets away from wildlife.
- Ensure dogs (and cats) are vaccinated against rabies and distemper, in case they have an unexpected incident with a raccoon.
Max, a 12-year-old Chihuahua from Greenfield, New Jersey, was euthanized recently after he was exposed to rabies. While far from unusual, the case highlights the ongoing risk of rabies exposure as well as issues with understanding of rabies guidelines and communication.
Max was attacked by a rabid raccoon - an ever-present risk for animals that go outside (or get outside) in many regions. Animal control was called and the raccoon was caught. It was euthanized and rabies was confirmed, indicating that Max was very likely exposed to the virus.
Here's where things seem to get strange. The paper reports:
"Once exposed to a rabid animal, a six-month quarantine is required for the exposed animal, even those animals that have been inoculated with a rabies vaccine."
- Not really. In Canada, standard guidelines are for a 6 month strict quarantine for dogs (and cats) that are not properly vaccinated, but only a 45 day observation period is required for vaccinated animals. I don't know if in this jurisdiction they made up their own different rules, whether someone doesn't know what's supposed to be done or whether it's poor reporting, but it's a concern because it can be a difference between life and death... not necessarily from rabies, but from the quarantine requirements alone. People are often unwilling to undertake a strict 6 month quarantine and choose euthanasia (as was the case here), while the 45 day observation period is much more acceptable.
The attending veterinarian stated "Because of the way it was exposed and because of the positive, I think there was a really good chance this dog was going to get rabies".
- It's certainly possible, and nowhere does it say whether Max was properly vaccinated. However, there's a reason we vaccinate. It's a highly effective vaccine and we're trying to prevent disease. Nothing's 100%, but with proper vaccination, the risk of rabies is greatly reduced.
It's also stated that "due to the nature of rabies, until behavioral changes occur, the animal is not infectious".
- While this doesn't have anything to do with Max's situation, it's not true. Animals can shed the virus for a short period before they show signs of illness. That's the reason there is supposed to be a 10 day quarantine period after a dog bites someone - to see if the dog develops signs of rabies (which would have major implications for the person who was bitten).
Curiously, the article ends with a reminder to vaccinate pets, which seems kind of strange if their assumptions are that an exposed animal will get sick irrespective of vaccination status and that vaccination will have no impact on what happens to an animal after exposure.
However, despite the miscommunication, the take-home message emphasizing the need for vaccination should be heeded. As well, people making decisions about what to do after rabies exposure should make sure they do so based on the best evidence that's available, namely the Compendium of Animal Rabies Prevention and Control.
The Ontario Ministry of Natural Resources and Welland SPCA are warning people about an apparently large number of cases of distemper in raccoons in the area. Distemper is a pretty nasty disease which can be spread between dogs and wildlife. It’s caused by canine distemper virus, but the "canine" part of the name can be a little misleading, since this virus readily infects some other species such as raccoons.
In addition to the problems with sick and dying raccoons caused by the outbreak, there are two main concerns for pet dogs:
One concern is the potential for wildlife to transmit canine distemper virus back to dogs. It’s hard to say what the risk of that is, and the risk would be primarily to young dogs that are not adequately vaccinated. If a dog has an encounter with a raccoon that is sick with distemper, it’s possible the pet could be exposed to the virus. Dogs are also probably more likely to have close encounters with sick raccoons that are unable or unwilling to run away, as opposed to healthy raccoons. If an inadequately vaccinated dog gets exposed, it can get very sick, which is obviously bad for the dog, and also creates another potentially infectious animal to keep passing the virus along.
The other concern is differentiating distemper from rabies. Distemper can cause signs that are very similar to rabies. If a dog has an encounter with a raccoon that is behaving abnormally, rabies is a big concern. If a dog is exposed and the raccoon is not available for rabies testing, the dog would require a 6-month strict quarantine or euthanasia if it's not vaccinated (or not adequately vaccinated), or a 45 day "observation period" (on a proverbial tight leash) if vaccinated. These measures aren’t easy to implement, and unvaccinated dogs often end up being euthanized because owners don’t want to go through the hassle of a 6 month quarantine.
What does this mean to the average pet owner? Well, nothing that they shouldn’t be thinking about anyway. This just increases the relevance of some routine measures such as:
- Keeping dogs that are outside are under control so they don’t encounter wildlife.
- Ensuring dogs are properly vaccinated against distemper and rabies.
- Taking particular care to prevent exposure of young unvaccinated dogs to wildlife.
- Discouraging raccoons from taking up residence in yards.
Nothing earth-shattering, but these basic precautions can greatly reduce the risk of disease transmission from wildlife to dogs, be it rabies, distemper or other bad bugs.
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.
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.
Raccoons are fascinating critters but they don't make good pets. Their curiosity makes them quite disruptive and damaging, and they have seriously injured people (particularly infants). They are also rabies vectors, and in many regions raccoon ownership (along with other wildlife species) is illegal (or only legal with a license). Despite all this, some people continue to keep raccoons as pets, and injuries continue to happen. Unfortunately, it's often not the owners that suffer the consequences, but children.
A one-week-old Griggville, Illinois baby is in hospital after being attacked by her grandparents' pet raccoon. The baby was in a room with the raccoon (not a good idea to start with), when the raccoon starting biting and scratching the baby's face and head. The raccoon's owner thinks the raccoon wasn't being vicious, just curious and trying to get a ribbon off of the baby.
"Rampy was trying to get the bow off the baby's head and it's got long claws and he was scratching up the head trying to get the bow off," said the owner.
Regardless, the fact that it caused severe injury indicates it's a hazard. (Wounds caused by accidents heal at the same rates as those caused my malice.)
Euthanasia of the raccoon was requested to test it for rabies. The owner countered that it had been vaccinated against rabies and dewormed (which raises the question of what veterinarian did this. I'd consider vaccinating and deworming an illegal pet unethical at best). Further, rabies vaccination does not guarantee that the raccoon isn't rabid. A judge eventually ordered the raccoon to be euthanized.
You'd think the raccoon's owners would be aghast at the attack. While I can see how they'd be attached to their pet, typically concern over a grandchild takes precedence. Not here, however, as the owners fought the euthanasia order and are railing against local authorities for having the raccoon euthanized after a potentially life-threatening attack. Even the infant's father is taken back by their attitude, stating "If it was somebody's dog that bit a kid, they'd be held accountable. These people should be held accountable for [the raccoon]."
In Canada, rabies testing and surveillance is performed by the Canadian Food Inspection Agency (CFIA). National data for 2010 are now available and indicate there were a small number of cases in domestic animals, with more in wildlife, for a total of 123 cases.
Dogs: There were three cases, all in Saskatchewan.
Cats: Four cases, three in Manitoba and one in Alberta.
Horses: One rabid horse in Manitoba.
Cattle: One, from Manitoba.
Skunks: 60 cases, 33 in Manitoba, 17 in Saskatchewan and 10 in Ontario.
Bats: 48 rabid bats, most in Ontario (29) but also in BC, Alberta, Saskatchewan, Manitoba, Quebec, New Brunswick and Nova Scotia.
Foxes: Six from the Northwest Territories or Nunavut.
No rabid sheep, goats, raccoons (down from 58 in 2007), wolves or other species.
Manitoba seems to win the 2010 rabies prize, while Newfoundland and Labrador, Prince Edward Island and the Yukon had no cases.
As with any disease surveillance, these numbers underestimate the scope of rabies. For an animal to appear on the list, rabies had to be considered and testing performed. So, for wildlife, it's a massive underestimation of the number of cases, since most affected wildlife don't get tested. Wildlife testing (and testing in general) is typically only done when there has been the potential for human exposure. Domestic animal cases are probably a fairly close representation of the status of rabies in pet and farm animals, since it's reasonably likely that a domestic animal with rabies would be identified as such and tested (although certainly cases can be missed or neglected). As with wildlife, there is probably an under-identification of rabies in feral/stray dogs and cats, since testing would only be done on these animals if they are caught and if there was potential human exposure.
- No? Maybe only if you're a high school wrestler from North Dakota.
On the way to the finals of a tournament, a busload of wrestlers came across a "dead" raccoon. For reasons that are unclear, they thought it would be a good idea to pick up the raccoon carcass and take it with them. They put it in the storage area of their bus and continued on their way.
Not only did that group of students display some questionable judgment by picking up the carcass, they also failed to notice that their "dead" raccoon was not actually dead. When they arrived at the tournament, the raccoon got up and ran away.
So, not particularly bright (or observant), but maybe not that big of a deal. Raccoons are important rabies vectors and a raccoon that allows itself to be loaded onto a bus by a bunch of high school students, and then later runs away, must be considered potentially rabid since you can't prove otherwise. However, you don't get exposed to rabies just by riding in the same bus as a napping raccoon. You have to have close contact with it (e.g. bite that breaks the skin, exposure of an open scratch/wound or mucous membrane (nose, mouth, eyes) to raccoon saliva).
In this case, however, the team was removed from the tournament when officials found out "they had been in contact with the wild animal and feared they may have contracted rabies." This makes no sense.
- If they were exposed, they'd pose no risk to anyone else at that point. You don't become immediately infectious after exposure. These students could not have transmitted the virus to other competitors.
- There was no evidence that they were actually exposed. No one was bitten or scratched.
Carrington school superintendent Brian Duchscherer said: "Once we found out, we didn't know if there was a potential of spreading anything or if the raccoon had rabies or not but we decided to bring our kids home." I would hope that a quick call to public health would have put those concerns to rest. Either they didn't bother to try to get good information or they got bad advice.
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.
A nine-month old Georgia (US) baby is in critical condition after being attacked by two raccoons while sleeping in her crib. The attack occurred in the middle of the night, and the baby ended up with severe bites over her head and other parts of her body.
It's not clear at this point whether these were pet raccoons that were being kept illegally or whether two raccoons broke into the house. If the latter, it's suspected that the family may have been feeding the raccoons, which could have made them less fearful of people than usual. The news clip also shows a large cage outside that could presumably house raccoons (pure speculation on my part here). Authorities are investigating whether these were illegal pets, and if so charges could result.
An unprovoked raccoon attack in a house is pretty strange. Raccoon attacks would be more likely in the raccoon's environment or if they were sick (e.g. rabies). They might also be more likely to try to break into a house if they have been fed by people and lost their fear of humans. Still, attacking a baby seems like a very strange thing for them to do. I also wonder whether an attack like this might be more likely with a pet raccoon, especially if it was an older, established raccoon in a household where a new baby had disrupted the routine.
Rabies has to be a major concern in a situation like this. One of the raccoons was killed by police. The news clip and article on the same website provide conflicting information about whether the other raccoon was caught. Both raccoons need to be tested to determine whether they had rabies. Otherwise, the baby will need rabies post-exposure treatment.
ProMed's monthly rabies update contains some recurring themes:
- A couple of incidents of dog versus rabid raccoon. The dog usually comes out on top, but the raccoon can exact revenge at the end of the day through the need for quarantine or euthanasia. If the dog is not vaccinated, a long quarantine or euthanasia is required. If the dog is vaccinated, only a shorter observation period is needed.
- A rabid skunk was found wandering around during the day with a wobbly gait and drooling. Any wild animal that is acting strangely should be considered rabid until proven otherwise. They don't have to be showing signs of severe neurological disease. Something as simple as not being afraid of people or wandering around in areas or at times when they would not usually be found should raise the suspicion.
- A child who was sleeping outside woke up to "find a raccoon, kind of, scratching at his leg." (I assume they mean it was "kind of scratching at the kid's leg," (whatever that means), instead of it was "kind of a raccoon.") The raccoon wasn't caught for testing but the child is undergoing post-exposure treatment because a normal raccoon wouldn't be expected to do that, so there is a significant chance of rabies exposure. Scratches are not high risk since rabies virus does not live in the claws, however it is possible that saliva from the raccoon could have been present on the animal's feet or the raccoon could have licked the child before scratching, such that the scratches could have then inoculated rabies virus into the tissues.
- A couple of reports of rabies in rabid kittens. These cute little rabies vectors cause repeated problems, and lead to public alerts notifying anyone who may have handled the kittens to get evaluated to see if they need post-exposure treatment. Handling of strays should be avoided.
- A family received post-exposure treatment after being bitten by their rabid cat. Vaccination of pets is not just for the health of the pet. It's to reduce exposure of people as well.
2009 animal rabies statistics have recently been published in the Journal of the American Veterinary Medical Association (Blanton et al 2010). Here are some highlights:
- 6690 rabid animals were identified, along with four human cases. (One of those human cases was associated with travel to India, as described as described in a recent post).
- Rabid animals were identified in 49 states and Puerto Rico.
- 92% of infected animals were wildlife. Raccoons were the winners (actually, the losers, I guess) with 2327 cases, followed by 1625 bats, 1602 skunks, 504 foxes, 300 cats, 81 dogs and 74 cattle.
It is important to remember that these are rabies diagnoses, not all rabies cases. Certainly, more animals died of rabies and were not tested. These numbers may represent the "tip of the iceberg," particularly for some wildlife species. This can impact on the accuracy of the relative numbers between species, and year-to-year changes in cases, but doesn’t change the fact that rabies is present, widespread, relatively common and can infect a wide range of animal species, including pets. It also highlights why vaccination of pets is still important.
Yet again, a large number of people are undergoing rabies post-exposure treatment because they were exposed to a rabid raccoon that was "adopted" from the wild. In this case, a North Carolina family found a baby raccoon at the side of the road and decided to bring it home. Over the next couple of weeks, various family and friends handled the raccoon, and many were bitten or scratched in the process. The raccoon then died and was identified as being rabid. Forty-five people are now being assessed to determine whether they need to be treated for rabies exposure.
The family dog, which was unvaccinated, has been taken by Animal Control and now faces either a six-month strict quarantine or euthanasia. I suspect the dog will be euthanized.
So, this probably well-meaning but misguided action has resulted in:
- the need for costly post-exposure treatment of many people
- presumably a stressful period for many of those people
- probably the death of the pet dog (although not having the dog vaccinated played a big role here too, since if it was vaccinated, it would only face a 45 day observation period at home, not a strict six-month quarantine or euthanasia).
Fortunately, the raccoon was tested. Otherwise we might be talking about human deaths from rabies, instead of people needing post-exposure treatment. The people who took in the raccoon could also face charges since keeping wildlife without a permit is illegal, but it sounds like that's unlikely to occur.
A few take-home messages from a situation like this:
- Leave wildlife in the wild.
- Vaccinate your pets.
- If you are exposed to an animal that is acting strangely, make sure it's tested for rabies (they did this right, at least).
- Roaming pets + wildlife = bad news: One person's dogs killed a raccoon while out for their "romp around the yard." The raccoon was rabid. There's no mention about the vaccination status of the dogs. If they were vaccinated, they probably got a rabies booster and are under a 45-day "house arrest" for observation. If not, they either need to be placed under a strict 6-month quarantine at a separate facility, or they'll be euthanized. Another report describes a different dog that is now under a 6-month quarantine after attacking a raccoon. In yet another report, a North Carolina woman's dog was euthanized because it killed a rabid fox and was unvaccinated (the owner chose euthanasia over quarantine). That dog is now dead mainly because the owner didn't take the simple and relatively inexpensive step of ensuring that her dog was vaccinated.
- Pissed-off wildlife bite. Sometimes they're rabid too. Get too close at your own peril: A South Carolina man is undergoing post-exposure treatment because he was bitten by a raccoon while removing it from a trap. I'm glad that he had the animal tested. It's pretty easy to see someone in a situation like this just yelling at the raccoon and letting it go, thinking they were bitten because the raccoon was upset and not realizing that they might have been exposed to rabies.
- Some people just don't get it: In response to rabies exposure of close to 50 church members from a rabid bat while on a mission trip, the mission leader stated "It's just part of being in rural America, so there's really not a lot to talk about." Ugh. Rabies exposure should not be written off as some benign, unavoidable rural American experience. It's exposure to an almost invariably fatal disease that requires a series of expensive treatments. It's also not a rural thing. Rabies exposures can occur commonly in urban areas as well.
- Stray kittens can be cute but deadly: A rabid cat and kitten were identified in Ocean City, Maryland, and authorities are looking for people that may have come into contact with them. Human exposure to rabies from handling cute but infected kittens is not uncommon, and sometimes involves a lot of people. If you see a stray kitten, it's best to leave it alone. If you feel the need to rescue it, make sure that you get it to a vet for an exam, and that it subsequently goes somewhere where it can be properly observed and taken care of. If you're bitten in the process, make sure the kitten is quarantined for 10 days to see if it's rabid, or euthanized and tested. The worse case scenario is when people play with stray kittens, get nipped in the process, dismiss it as a minor or playful bite, then release the kitten back into the wild, never knowing whether they might have been exposed to rabies.
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.
The Toronto Star had a front page article today about an ongoing distemper outbreak in raccoons, and the potential effects on dogs. Toronto's not alone, as there are distemper outbreaks underway in many different municipal regions.
Distemper is an infection caused by a virus that is related to human measles virus. It mainly affects dogs, raccoons and ferrets. It can cause intestinal, respiratory and neurological disease, with neurological problems being the most severe. Vaccination of dogs against distemper is highly effective, and has greatly reduced the impact of this virus on the pet dog population.
Distemper cannot be transmitted to people, so the disease itself is only an animal health risk. However, there's an indirect effect of which people need to be aware. Rabies always needs to be considered in dogs and raccoons that have signs of neurological disease. If there is so much distemper in an area that people assume every sick (wild) animal they find has distemper, there is a risk that the odd (but important) case of rabies may be missed, leading to human exposure. It's easy to dismiss a neurological raccoon or unvaccinated dog as having distemper, and it usually is distemper (particular in light of the current outbreak), but the implications of missing a case of rabies can be severe since it can be transmitted to people and is almost invariably fatal.
If distemper is present in your area (or, really, even if it's not currently a problem):
- Make sure your dog is vaccinated.
- Keep your dog away from wild animals, especially ones that are acting strangely.
- Keep yourself away from wild animals, especially ones that are acting strangely.
- Don't do things that will encourage raccoons to move into your yard, like leaving out food.
- If you see a wild animal that is acting strangely, call your local animal control agency.
Photo credit: The Star - Toronto edition 18-Feb-10
Eight more rabid raccoons have been found in New York's Central Park over the past two weeks. These, plus the 12 rabid raccoons reported in the park last year, represent a major increase in disease frequency since only 1 rabid raccoon was identified in Central Park from 2003-2008. That's a concerning development given the number of people that visit this 843 acre park in the heart of New York city every day.
In response, the city's Health Department has started an education campaign to alert people to the risk, and tell people to stay away from wildlife, report any sick animals and to keep their dogs on leashes. Every pet owner also needs to make sure their dog's rabies vaccine status is up-to-date, even if they always keep their dog on a leash, because you never know what a rabid raccoon will do (such as attacking a leashed dog that walks by). There are also plans to vaccinate raccoons in and around the Park, however I couldn't find details about what type of vaccination program will be used.
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.
When we have a -30C windchill and snow on the ground, my first thoughts usually aren't about survival of bacteria in the outdoor environment. However, some microorganisms are well adapted for survival in various adverse conditions and we shouldn't assume that cold=dead for every bug of concern. Along that line, we received a question recently about survival of Leptospira and I passed it along to our lepto expert, Dr. John Prescott. Here's his guest post:
A reader in Ohio owns a dog that had leptospirosis, and had some questions about leptospirosis that may be of general interest.
Q1. Since the yard is likely contaminated with leptospires, she asked “How cold does the temperature have to get before the Lepto organisms are killed?”
A1. Once it’s frozen, as it is now in January, they’re dead. Leptospires are fragile bacteria that are killed by dry heat and by freezing. They survive well in moist or wet environments, with moderate temperatures. In some countries leptospirosis is called “mud fever” or “fall fever” since this description captures so well the environmental conditions under which they thrive.
Although leptospirosis in dogs can occur at any time in the year, it mainly causes disease in the fall, late September to December, peaking in November. The increasingly mild and prolonged falls that we have experienced in the last decade are thought to be an important reason that leptospirosis has resurged in dogs. Interestingly, there is often a “blip” of leptospirosis in dogs in March in Ontario (and likely Ohio), since this is when the snow melts and conditions are wet, even though we can still get freezing at that time. I suspect that this is also the time when the raccoons that are thought to be the main source of leptospirosis for dogs are again active after the winter, and are foraging for food for themselves and their babies.
Q2. Do dogs still shed leptospires after they’ve been treated?
A2. No. Leptospires are quickly killed by the antibiotics used in treatment, amoxicillin or doxycycline. There is no danger that dogs treated for a week with these drugs are a risk to people or other animals. You may read in otherwise very reputable textbooks that these antibiotics “do not eliminate the carrier state” but I have no idea where this misunderstanding comes from.
Q3. Where can I find out more about leptospirosis in dogs?
A3. I like the web site http://www.leptoinfo.com, which is maintained by a vaccine company. I was surprised how many web sites devoted to leptospirosis that there are, but like much on the internet some contain highly misleading information. The “Worms & Germs” site has good past blogs about canine leptospirosis and is usually (just kidding, Scott) a reliable source of information.
One very common entrenched misconception, which is very hard to kill, is that vaccination does not stop animals shedding the organism. This is quite wrong. I suspect this misconception came from an experimental study half a century ago when dogs with pre-existing kidney infection with a leptospiral serovar called Canicola were vaccinated. It would not be expected by anyone that these animals would stop shedding since antibodies don’t penetrate into the place in the kidney where the leptospires live and from which they are shed in the urine. What vaccination does incredibly effectively is to prevent leptospires from actually reaching the kidney and setting up home there. The leptospires are removed by antibodies in the blood, so they never reach the kidney.
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.
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.
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.
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.
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.
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.
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.
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.
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.