Infection from raccoon to parrot
An article in the May/June edition of Canadian Vet Newsmagazine (a magazine, not to be confused with Canadian Veterinary Journal, a scientific journal), described an interesting case of an indoor pet bird acquiring an infection from a wild raccoon, despite no direct contact.
The bird was an African Grey Parrot that was admitted to the Ontario Veterinary College because it had developed neurological abnormalities over the preceding few weeks: a head tilt, unsteadiness and problems climbing. Infection of the brain caused by the raccoon roundworm Baylisascaris procyonis was suspected and treatment was started, however unfortunately (but not surprisingly) the bird continued to deteriorate and was eventually euthanized. Baylisascaris infection was confirmed at necropsy.
Baylisascaris procyonis, the raccoon roundworm, is extremely common in raccoons, with the majority of raccoons in some areas shedding the eggs of this parasite in their feces. The eggs are extremely hardy and can survive for long periods of time in the environment. The tendency of raccoons to defecate in the same areas (raccoon latrines) means that very high concentrations of eggs can be found in some spots. While this is a raccoon-origin parasite, it can occasionally cause infection in other species (including people and dogs, albeit very rarely). After ingestion of the parasite eggs, the eggs hatch and parasite larvae migrate through the body, causing damage to various tissues as they go. If they migrate through the brain, severe neurological disease can occur.
An interesting aspect of this case is the fact that it was an indoor parrot. If this was a dog that had been exposed to a raccoon latrine, while it would have been a rare occurrence of disease, the origin of infection would have made sense. Here, the parasite eggs had to somehow make it into the house and then into the parrot. The suspected source was branches that were collected from the backyard and placed in the bird's cage. The branches were presumably contaminated with Baylisascaris eggs, and the bird ingested some while chewing on the branches.
This is a very rare situation, but the article includes some basic recommendations:
- Never adopt a raccoon (for many reasons beyond the Baylisascaris risk to pet birds).
- Don't keep parrots in outdoor enclosures where raccoons have access.
- Don't put parrots in outdoor enclosures that may have previously housed raccoons.
- Avoid putting objects from raccoon-inhabited areas into parrot cages or treat them to kill eggs. Heating objects to 62C for 1 minute should kill any eggs that are present.
- Ensure that cage bedding and bird feed are not potentially contaminated with raccoon feces.
Reducing risks with raccoon latrines
An interesting paper in the journal Emerging Infectious Diseases (Page et al. 2011) describes an impressively large effort to study the effect of anthelmintic (dewormer) baiting on parasite contamination at raccoon latrines sites in Indiana.
Raccoon latrines can be highly contaminated with various parasites, because raccoons congregate at these sites and use them as "communal toilets." Of all these parasites, the raccoon roundworm, Baylisascaris procyonis, gets the most attention. It is very common in raccoons, but it is also a very rare cause of disease in people who swallow the infective parasite eggs from the environment. In some of these people the parasite larvae can cause very serious neurological disease which can be very difficult to treat.
In this study, the research team identified 559 raccoon latrines in north-central Indiana. They removed debris from the areas and used a torch to help kill the parasite eggs that were there (this is one of the very few effective ways to kill the very hardy eggs of Baylisascaris). At a selection of latrine sites, they also collected baseline fecal samples. After this was all done, they distributed dewormer (pyrantel pamoate) baits in half the areas once a month (leaving the other half of the areas as controls). They then collected fecal samples at all the latrine sites approximately 6, 12 and 18 months later.
Fecal samples were tested for B. procyonis eggs. Also, they captured mice from some of the study patches. Like people, mice are intermediate hosts for B. procyonis, and they can be infected in the same manner, so researchers looked for B. procyonis larvae in the brains of the mice.
Overall, they tested 1797 fecal samples. In the first round of sampling, 33% of samples contained B. procyonis eggs. The prevalence of eggs decreases significantly (3-fold) after baiting by the first recheck, and stayed at that level throughout the study. By the one-year sample time, there was also a significant decline in B. procyonis larvae in the brains of mice (27% vs 38%).
This impressive study shows the potential impact of controlled and somewhat practical interventions on the presence of some concerning microorganisms. Certainly, no one is going to be able to treat all raccoon latrines with a torch. However, dewormer baiting might be a consideration in areas that are close to human populations, along with other control measures. Dewormer baiting could be relatively cost-effective in this case. It won't eliminate the problem, but it might help reduce environmental contamination and the associated potential for human and domestic animal exposure.
More information about Baylisascaris and raccoon latrines is available in our archives.
Baylisascaris and dogs
Recently, I was speaking with a physician who mentioned that a colleague has recommended that people with raccoons in their yard get rid of their dogs because of the risk of Baylisascaris procyonis. This parasite, also known as the raccoon roundworm, can cause severe neurological disease in people that ingest infective parasite eggs from the environment.
The most severe type of disease caused by the migrating larvae of this roundworm (neural larval migrans) is very nasty, and usually causes death or serious, severe neurological deficits. However, the recommendation to get rid of dogs when there are raccoons around makes no sense. Here's why:
- The main host for Baylisascaris is the raccoon. A large percentage of healthy raccoons (over 90% in some areas) are infected and pass large numbers of parasite eggs in their stool. Exposure to eggs from raccoon feces is the main source of human infection.
- Human infections are very rare. They predominantly occur in people that are at increased risk of ingesting feces or dirt, based on their age or behaviour.
- Dogs can be infected with Baylisascaris, but this is rare.
- The small number of dogs that are shedding Baylisascaris in their feces do not pose an immediate risk to people. Eggs that are passed in feces are not immediately infective. Eggs must mature in the environment (which usually takes 2-4 weeks) before they are able to cause infections.
- There are no clearly documented cases of dogs being a source of human infection.
- The main risk from dogs is probably the potential for dogs to carry old (i.e. infectious) Baylisascaris eggs into houses on their haircoats, after roaming around raccoon infested areas.
How do you reduce the already very low risk associated with Baylisascaris and dogs?
- Discourage raccoons from living near your house. Raccoons defecate in certain areas or "latrines," where the soil becomes heavily contaminated with raccoon feces, and where tremendous numbers of infectious eggs can be present. If you make your yard uninviting to raccoons, then they won't establish a latrine near your house.
- Carefully clean any raccoon latrines that might be on your property.
- Don't let you dog have contact with raccoon latrines.
- If your dog has had contact with a raccoon latrine, give it a bath. Baylisascaris eggs are sticky and can stick to the dog's coat quite well, so a thorough bath is much better than a quick rinse or brush. Wear gloves and some form of protective outwear (e.g. a coat that you take off after and promptly launder) while bathing the dog. Wash your hands thoroughly when done.
- Closely supervise people at increased risk of ingesting feces or dirt (e.g. young children) when they're outside.
- A routine deworming program will eliminate Baylisascaris in the intestinal tract of a pet dog, in the unlikely event it's been infected.
- Prophylactic treatment of dogs that have eaten (or have a tendency to eat) raccoon feces could be considered, but the need and usefulness of this is not clear.
Bottom line: You don't need to get rid of your dog if there are raccoons in your yard. The risk of Baylisascaris infection from your dog is extremely low, and the steps above can help you decrease the risk even further. Getting rid of the raccoons (instead of the dog) will be much more effective.
More information about Baylisascaris and neural larval migrans is available in our archives.
Baylisascaris in Winnipeg
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There was another paper published in the August issue of the Canadian Veterinary Journal about Baylisascaris procyonis (roundworms) in raccoons, this time in Winnipeg, Manitoba (Sexsmith et al 2009). The study was actually undertaken after infection with B. procyonis larvae was identifed as the cause of death of several animals in the collection at the Assiniboine Park Zoo in Winnipeg.
The researchers collected feces from 52 active raccoon latrines around the city and from 114 "nuisance" raccoons that were caught, euthanised and submitted for necropsy to the local lab. Interestingly, the vast majority of latrines and nuissance raccoons were found close to the two major rivers that run through Winnipeg. Half (50%) of all the latrines were positive for roundworm eggs on at least one sample (out of a possible 3). Among the necropsied raccoons, 61/114 (53.5%) were positive for roundworms. Adult raccoons were almost four times as likely to carry roundworms than juveniles (which is in contrast to a previous study that found juveniles more likely to be infected), and bigger raccoons (over 2.75 kg) were more than seven times as likely to carry roundworms compared to smaller animals. Although there are regions where the prevalence of B. procyonis s reported to be very low, Winnipeg, like many other regions of North America, has joined the ranks of those where the prevalence is high and the public needs to be aware of the associated risks.
The most severe zoonotic disease caused by B. procyonis is called neural larval migrans (NLM), which results from migration of parasite larvae through the central nervous system (i.e. brain). Two of the reasons this is much more of a concern with raccoon roundworms (Baylisascaris) compared to dog and cat roundworms (Toxocara) are:
1) A massive number of parasite eggs are passed in the feces of infected raccoons (which typically have a very high burden of adult worms). Coupled with the fact that the eggs are further concentrated in areas where many raccoons defecate (latrines), this can lead to heavy exposure of people (or animals) who come in contact with the soil in these areas, which greatly increases the risk of infection.
2) The larvae of B. procyonis are very active migrators, and they get bigger as they migrate through tissues - much bigger than Toxocara larvae ever get, which means they also tend to cause a lot more damage before they're finally (if ever) trapped or killed by the body's immune response.
Natural infection of dogs living in the same areas as raccoons has been found - it's not common, but it appears to occur frequently enough to warrant noting. Dogs and cats can also be infected by their own species of roundworms, which will also result in parasite eggs being shed in the feces. It's important to have your veterinarian perform a fecal examination for your pet on a regular basis so any parasite infestations (roundworm or other) can be treated.
Dogs and cats may also be susceptible to larval migrans in the same manner as people (and the animals at the zoo in Winnipeg) if they are exposed to high numbers of infectious eggs. Remember that roundworm eggs must be swallowed in order for infection of any kind to occur, so good hand hygiene and avoiding soil contamination of food are key to preventing transmission. Also, do not allow your pet to dig or play in an area where raccoons defecate (preventing direct contact between your dog and raccoons should go without saying!). And of course, feces of any kind (and from any species) should be treated as infectious material, and handled with appropriate precautions.
More information about Baylisascaris and raccoon latrines is available in our archives.
Raccoon deterrents
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We've written various posts about raccoons, raccoon latrines and concerns about the raccoon roundworm (Baylisascaris procyonis). I received a question today about how to keep raccoons from coming back after a latrine has been identified and cleaned. It's a good question, and one without a simple answer. I've looked through various sources and have found a wide range of recommendations. (Whenever I see such a wide-ranging list of recommendations, I wonder whether anything actually works.)
Home remedies include:
- Sprinkling pure soap flakes on the lawn and watering thoroughly
- Mixing bone meal in garden soil
- Sprinkling diluted tabasco sauce over fruits and vegetables (wash before eating, as you should anyway!)
- Lighting up the area where raccoons are a problem
Various commercial deterrent compounds are available, such as one that apparently has the scent of a coyote, or one that's a combination of vinegar, pepper and sulfur.
Another approach is motion-sensitive deterrents. Motion-sensor-based lights can be useful since raccoons often come rooting around in the evening or overnight, and lights that turn on when they approach could be effective. These would require a power source, which could be limiting in some places like sheds. Similarly, motion-sensor based systems that spray water or citronella (sometimes used to keep cats out of certain areas or off countertops) could be useful. Battery-operated units could be used anywhere. (Here's a link to one. I've never used it but it shows you what I'm talking about). There are also motion sensors that hook up to hoses.
One problem with deterring raccoons is their intelligence. They can often find ways around deterrents, or adapt to them. Along with any attempts to actively deter the raccoons, it is also important to try to reduce the desire of the raccoon to come to the location. If there is a good food source or other desirable attraction, the raccoon will probably try harder to stay around. Tightly covering garbage cans and removing other possible food sources (e.g. food for outdoor cats) are important steps. Making sure neighbours (or other family members) aren't feeding the raccoons is also important, because food is a great motivator.
Raccoon latrines in Chicago
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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.
Cleaning up raccoon latrines
Raccoon latrines are a major source of eggs of the raccoon roundworm, Baylisascaris procyonis. Accidental ingestion of large numbers of eggs from these latrines can lead to a disease known as visceral larval migrans. The most severe forms of this condition are known as ocular or neural larval migrans, which are damage to the eyes or brain/spinal cord (respectively) due to the roundworm larvae migrating through the body tissues. The disease is very rare, but the consequences are very severe. Previous Worms & Germs posts have discussed Baylisascaris and larval migrans in more detail.
Raccoons tend to form latrines - areas where they will return to deposit stool repeatedly. In some ways this is handy, because it means you generally don't find raccoon stool all over the place. On the other hand, the latrines themselves contain large amounts of stool, and along with that are large numbers of Baylisascaris eggs, not to mention bacteria and sometimes fungi. So it is important to recognized latrines, particularly when they occur near your house, garden, or anywhere children may play. Raccoons like to used flat, raised areas for latrines, such as roofs, decks, woodpiles, fallen logs or even large rocks, just to name a few.
Cleaning up raccoon latrines warrants some special precautions in order to avoid swallowing the roundworm eggs and to avoid spreading them around. Recommendations include:
- Wear rubber gloves, and always wash your hands thoroughly when you are done.
- Wear disposable overboots, or rubber boots that can be scrubbed and disinfected.
- Wear an N-95 rated particle mask if you are cleaning up a latrine in an enclosed space, such as an attic or crawl space.
- Thoroughly wash your clothes with soap and hot water when you are done, and dry them completely.
Follow this link for detailed information on how to clean up a raccoon latrine. A few of the more important points about dealing with these latrines include the following:
- Avoid stirring up dust. Misting the area with water first can help with this.
- Double-bag and carefully dispose of any garbage/debris you remove from the area.
- Most chemicals will not kill roundworm eggs. Removing the eggs is usually the best option, but extreme heat will also kill eggs instantly. Flaming contaminated areas can be effective, but contact your local fire department about local regulations and safety precautions before attempting to flame a latrine site.
