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.
Baylisascaris (raccoon roundworm) in cats
A reader posed this question, with respect to having raccoons living around the house:
"One thing that causes me concern with the raccoon roundworm is the possible danger of infection to my pets and myself through the feces left behind from the raccoons in the yard and possibly in my vegetable garden. Can I acquire the roundworm from working in the soil and/or from my root vegetables etc? My cats mingle near the raccoons, they don't bother each other, should I get my cats tested?"
Certainly, working outside (particularly in soil) leads to the potential for exposure to many disease-causing agents, including Baylisascaris, as well as dog and cat roundworms (Toxocara spp.). Eating unwashed/uncooked vegetables is also a risk. However, in the grand scheme of things, the risks to the average person (not very young or very old, functional imune system) are minimal, especially if basic hygiene measures are used, such as washing hands after working in the garden, and thoroughly washing vegetables. Raccoons tend to defecate in the same specific areas most of the time (raccoon latrines), so in general gardens probably aren't common sites for raccoon feces, although it certainly can occur. Cats are probably more likely to defecate in gardens. We shouldn't take concerns about Baylisascaris lightly, because even though disease (larval migrans) is very rare, it can be very severe.
Now, about testing cats for Baylisascaris - there's not much use, for several reasons:
1) The likelihood of a positive result is very low. The prevalence of Baylisascaris in dogs is very low. Little is known about the prevalence in cats specifically, but it is presumably very uncommon there as well.
2) It can be difficult to differentiate Baylisascaris from the feline roundworm, Toxocara cati. Unless the lab has experience with this, they may not be able to tell the difference. Therefore, you might get a misleading result.
3) What does a positive test tell you? It tells you that the cat is shedding this parasite or that is has ingested eggs that are just passing through the intestine. The risk to people is still minimal if litterboxes are cleaned regularly. Contaminated stool is not infective until it has sat around for days to weeks, so regularly cleaning the litterbox and good handwashing can control the risk.
4) What does a negative test tell you? It tells you that the parasite was not detected on this single sample. It could have been there but not been identified. It might not be there today but could be there tomorrow (though this is still unlikely). A single negative test today does not tell you too much.
5) What would you do with the results? Probably not much. In the very unlikely chance that results were positive, it would likely be recommended to repeat testing to see if eggs are just passing through or whether the animal truly is infected with the parasite. That would determine whether treatment is needed. Otherwise, recommendations would be pretty much the same in both cases (good regular deworming program as directed by your veterinarian, proper handling of cat feces...).
The best way to prevent exposure of your cat to Baylisascaris (as well as other pathogens, predatory wildlife, vehicles, etc.) is to keep it inside.
Garden veggies and poopy parasites
Spring appears to have finally sprung in earnest in Southern Ontario (although we may still get one more frost on the weekend, so I hear) and people are getting back out into the garden. An increasingly popular trend in recent years, particularly this year now that the Obama's are doing it too, is vegetable gardening. Lots of people like the idea of growing their own veggies in their own backyard, or perhaps in a community garden plot for city dwellers who still want to get their hands dirty - it's economical, good for the environment, and the plants can be grown "organically" without the use of chemicals or pesticides. However, pesticides and garden bugs aren't always the only things to worry about having on your fresh veggies. We received the following comment from a Worms&Germs reader:
"...What if veggies get infected with raccoon stool[?] Can eggs be killed after [the] veggie is grown and ready to eat?"
Great question. The concern in the case of raccoon stool is the eggs of the roundworm Baylisascaris procyonis, which can be passed in huge numbers by a relatively high percentage of raccoons in many regions. If swallowed, the eggs release larvae which can migrate through the tissues of the body, rarely causing visceral, ocular or neural larval migrans.
The good news:
- Raccoons like to defecate in the same areas most of the time, usually on a relatively flat, elevated surface (e.g. woodpile). These areas become raccoon "latrines", and the soil in the area can become very heavily contaminated with roundworm eggs. The good part is that most raccoons therefore not defecate in your garden.
- Vegetables cannot become "infected" by the parasite - the eggs cannot be absorbed or otherwise get inside a vegetable, they can only contaminate the parts of the plant that are directly in contact with soil.
The bad news:
- Even though raccoons may not poop in your garden, they can still track roundworm eggs into the soil on their fur or paws when they come by to explore your crop, so you should always consider soil outside as potentially contaminated.
- Baylisascaris eggs are highly resistant to disinfectants and chemicals, so they can't be killed this way.
- Raccoon roundworms aren't the only parasites that may be found in garden soil. Dogs and cats can carry other roundworms (Toxocara spp.) which are also capable of causing larval migrans if swallowed (although infection with these worms in dogs and cats is not nearly as common as infection with Baylisascaris in raccoons). Cats in particular, unfortunately, do sometimes like digging in gardens and may sometimes use a garden as a litterbox.
- Soil, particularly if it's contaminated by the stool of any animal, can also contain many different kinds of bacteria such as Salmonella. Even if you can somehow protect your garden plot from animals, purchased garden soil and fertilizers may contain or may have come in contact with animal stool somewhere along the way.
So how do you make your garden veggies safe to eat?
- Wash wash wash: Because Baylisascaris eggs are so difficult to kill, the best thing to do is physically remove them from all surfaces of your vegetables by washing thoroughly to remove all visible dirt before doing anything else. If you cut into a vegetable before washing it, the soil on the outside can contaminate the inside.
- Peel peel: Peeling vegetables ensures that all dirt (including any dirt stuck in tiny crevices on the vegetable's surface, or dirt you may not be able to see with the naked eye) is removed prior to consumption, but it's still crucial to wash the veggie first (and your hands) before peeling.
- Cook: From an infection control perspective, it's best to cook vegetables before eating them. This actually won't do anything to Baylisascaris eggs - these have to be removed by washing and peeling - but it does help kill bacteria that either contaminated the veggies out in the garden or that contaminated the veggies during their preparation in the kitchen. For those of us who like our nice crunchy vegetables, obviously cooking them won't do, therefore washing and peeling become that much more important.
And, of course, always wash your hands thoroughly with soap and water after you've been working in the garden, even if you wear gloves.
In a lot of urban areas, it's hard to prevent raccoons and other animals from getting into yards and gardens. There are things you can do to discourage raccoons from hanging around your house, and if raccoons establish a latrine on your property it must be very carefully cleaned up. For more information on Baylisacsaris, raccoons and cleaning up raccoon latrines, please see our archives.
Raccoon roundworm in New York
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ProMed mail has a report about 2 cases of Baylisascaris procyonis infection in people in Brooklyn, New York. Baylisascaris is the raccoon roundworm and is very commonly found in the intestinal tract of healthy raccoons. Raccoons shed this parasite in their stool, and after a short period of time, the parasite larvae become infective to other animals and people. Infective larvae can survive for a long time in the environment. People become infected by swallowing the larvae that can be found in dirt or on any object contaminated by raccoon stool. Disease in humans due to this parasite is rare but can be extremely severe.
The first case in this report involved an infant with neural larval migrans, a condition caused by migration of the roundworm larvae through the brain. Despite treatment, the child now has permanent brain damage because of this disease. Unfortunately, this is not uncommon consequence, as the infection is not usually identified until severe and irreversible damage has already occurred. The child had a history of eating soil, and swallowing soil contaminated with raccoon feces is the most likely source of infection.
The second case involved a 17-year-old with ocular larval migrans, which is caused by migration of the parasite larvae through the eye. The parasite was killed using laser therapy, however the patient lost all vision in the affected eye before the infection was identified. There was no mention of where or how the teenager may have been exposed. Infection of someone of this age is very uncommon, as most 17-year-olds are much less likely in ingest (intentionally or accidentally) raccoon stool. It would be useful to know whether this patient had a developmental disability which results in an increased likelihood of swallowing dirt or feces, or whether there may have been some other type of exposure.
Baylisascaris infections in people are extremely rare, despite the fact that a large percentage of raccoons carry this roundworm. This report of two cases occuring in the same area within a few months of each other is surprising. Hopefully it's just a bad coincidence, and not an indication of some change in the incidence of this disease. Avoiding Baylisascaris means avoiding ingestion of raccoon stool. Sounds simple enough, but this is of particular concern with young children and people with developmental delays who are more likely to swallow contaminated dirt or stool, or put dirty/contaminated hands or objects in their mouths.
More information about Baylisascaris and preventing transmission of the infection can be found in our archives, as well as information about cleaning up raccoon latrines.
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.
Updated: Speaking of Baylisascaris...
This post has been updated with new information as of October 2, 2008.
An article was published on Sunday in a local Guelph newspaper about a 14-month-old child who has been battling infection with Baylisascaris larvae in a Hamilton (Ontario) hospital for the last two weeks. This comes on the heals of a very recent Worms & Germs post about Baylisascaris procyonis - the raccoon roundworm.
The disease caused by migration of Baylisascaris larvae through the body - visceral larval migrans - is uncommonly diagnosed in North America, although it may be more common than we think because it is difficult to diagnose with certainty, and the signs in mild cases may be very non-specific. The most severe form of the disease is called neural larval migrans, which occurs when the larvae migrate through the brain or spinal cord, as in this most recent case.
The parents of the toddler in the article, a toddler who is still blind and cannot sit up on his own as a result of his infection, have a message for parents: keep raccoons out of your yard and away from your house. The disease may be rare, but the effects can be devastating, and the risk can be significantly reduced by a few simple steps:
- Keep garbage in tightly-sealed containers.
- Clear brush and seal openings in buildings where raccoons may nest or form latrines.
- If you find raccoon stool or what appears to be a raccoon latrine on your property, clean it up very carefully. Follow this link for more information on identifying and cleaning up raccoon latrines.
- Always wash your hands well after you've been working outside in soil, dirt or water which could be contaminated with raccoon feces.
For more information, see the last Worms & Germs post about Baylisascaris.
Updated: Raccoon Roundworms - Baylisascaris procyonis
This post has been updated with new information as of October 2, 2008.
Raccoons, just like dogs and cats, can have roundworms in their intestine. Dogs are typically infected by the species Toxocara canis, and cats are infected by Toxocara cati. Raccoons are infected by a type of roundworm from a different genus, called Baylisascaris procyonis. There is one thing that all three of the parasites have in common – the larvae of these worms can infect humans, causing a condition called visceral larval migrans.
Dogs and cats are usually dewormed as puppies and kittens, and often as adults as well, which dramatically decreases the number of pets that are infected with roundworms. Raccoons are not so lucky – in the northern and northeastern parts of North America, over 70% of raccoons may be infected with Baylisascaris. In Ontario, it has been estimated that only about 20-30% of raccoons are infected, but usually with high numbers of worms. In either case, younger raccoons are even more likely to be infected. Infected animals may shed millions of parasite eggs in their stool, and the eggs can survive in the soil for months or even years.
After a few weeks, the eggs in the raccoon stool become infective. If a person swallows the eggs, they hatch in the small intestine and release larvae. These larvae can then burrow through the wall of the intestine and migrate through tissues all over the body, causing tissue damage and inflammation. The signs of illness are often not very specific, and may include things like fever, fatigue and nausea. If the larvae migrate through the brain or spinal cord, a person may develop neurological signs like loss of coordination and muscle control. This is called neural larval migrans, which is the most serious type of disease caused by these larvae. If the larvae migrate through the eye, they can cause blindness. This condition is known as ocular larval migrans.
There have been less than 25 cases of confirmed visceral larval migrans due to Baylisascaris in the USA as of 2003, but the condition is very hard to diagnose with certainty, and it is possible that many cases are mistaken for other illnesses. The disease is also very difficult to treat, and neurological damage from neural larval migrans is usually permanent, so the best thing to do is prevent infection in the first place. Here are some tips on avoiding Baylisascaris:
- Avoid contact with raccoons. Many people think raccoons are cute, but they are wild animals. Raccoons are also a risk for transmission of rabies if a person is scratched or bitten. NEVER keep a raccoon as a pet.
- Discourage raccoons from hanging around your house. Clear brush and seal access to basements and attics where raccoons may try to nest or form latrines. Keep garbage in tightly-closed garbage cans. Eliminate outdoor water sources.
- Always wash your hands well with soap and water after working with soil (e.g. in the garden).
- Clean up raccoon latrines. This must be done very carefully - avoid getting any raccoon stool on your hands or clothes. The stool should be burned, buried or sent to a landfill. Clean the area where the stool was found with boiling water. Wash your hands very carefully when you’re done. Follow this link for more detailed information on how to identify and clean up raccoon latrines.
Baylisascaris procyonis less commonly infects animal species other than raccoons, including skunks, and it has even been found in dogs. It's important to have your dog's stool examined for parasite eggs on a regular basis (typically once or twice a year) and to follow your veterinarian's recommendations for deworming your dog.
More information about Baylisascaris is available on the CDC’s Baylisascaris Infection website.
