Raccoons and dogs can harbor adult B. procyonis in their intestinal tracts
A wide variety of vertebrates can serve as paratenic hosts that harbor larval Baylisascaris sp. infections
Baylisascaris procyonis larvae have caused visceral disease and death in more than 100 species of vertebrate hosts.
Paratenic hosts infected with larvae, e.g., primates, rabbits, cats, and birds, can develop signs of infection similar to those seen in children with visceral larva migrans.
Baylisascaris procyonis has a 7- to 10-week prepatent period in raccoons following ingestion of larvated eggs, but patent infections may develop in as little as 4 to 5 weeks upon ingestion of larvae in a vertebrate paratenic host.
Nonembryonated eggs passed in the feces of raccoons or dogs require at least 10-14 days in the environment to larvate and develop into the infective stage. Because of the time required, fecal material has often broken down before the eggs are infective, and thus there is often no gross evidence that the environment is contaminated with infective eggs. However, once present, eggs are hardy and can survive and remain infective for years.
Removing eggs from a contaminated environment is difficult, and common disinfectants are not effective at killing them. Strict adherence to leash laws and prompt removal of dog feces are essential aids in the prevention of ascarid infections.
Because raccoons are the primary host, never provide outside food that attracts raccoons into areas where humans live.
Routinely deworming infected animals before the infections become patent will prevent environmental contamination and is another key component of achieving effective control (see Control and Prevention below).
The most severe pathology with B. procyonis is associated with migration of larvae in the central nervous system.
Adult ascarids in the small intestine of dogs are not known to cause disease but, similar to other ascarids, could cause enteritis and mild diarrhea. Although dramatic cases of intestinal obstruction and intussusception associated with large numbers of worms in the small intestine have been reported in raccoons, such sequelae are considered rare and have not been described in dogs.
Eggs of B. procyonis can be difficult to distinguish from those of the more common Toxocara spp., although morphologic differences exist (see under Life Cycle) and differentiation becomes easier with experience.
PCR (provides differentiation between the two species)
Routine testing and deworming of all dogs is recommended (see Treatment).
Most of the drugs known to remove T. canis from dogs (fenbendazole, milbemycin oxime, moxidectin, and pyrantel pamoate) will also remove Baylisascaris spp. although no treatments are label-approved for this use and retreatment may be needed to eliminate the infections.
To avoid contamination with eggs of B. procyonis, raccoons should not be kept as pets and people and dogs should avoid areas frequented by raccoons.
To treat potential newly acquired infections, dogs should be maintained on monthly intestinal parasite control products with efficacy against ascarids.
Efficacy of the initial dewormings, monthly control product, and client compliance should be monitored by performing a fecal examination 2 to 4 times in the first year and 1 to 2 times per year thereafter, depending on the age of the animal and its prior history of infection.
Keeping dogs confined to a leash or in a fenced yard will prevent predation and scavenging activity and limit the opportunity for dogs to acquire infection with Baylisascaris via ingestion of paratenic hosts or from an environment contaminated with feces from raccoons.
Prompt removal of feces from the yard will also help prevent ascarid eggs from remaining as the fecal material decomposes or is dispersed into the environment.
Enforcing leash laws and requiring owners to remove feces deposited by their dogs can protect public areas from contamination with ascarid eggs.
Baylisascaris procyonis causes disease in people following ingestion of larvated eggs from a contaminated environment. The larvae of B. procyonis migrate extensively in the central nervous system, commonly resulting in severe neurologic disease in affected individuals; B. procyonis can also produce visceral, ocular, and covert forms of disease.
Prevention of disease caused by infection with B. procyonis requires preventing the ingestion of eggs from the environment. Young children should be closely monitored so that eating dirt and other forms of pica can be discouraged, particularly in public areas known to be frequented by dogs or populated with raccoons.
Early, regular deworming is essential in preventing contamination of the environment with ascarid eggs, including those of B. procyonis. Treating dogs to prevent egg shedding is critical because the eggs are very hardy and long-lived in the environment. Once present, the eggs can be removed or destroyed only through extreme measures such as paving kennel areas or areas where pets defecate with concrete or asphalt, complete removal of topsoil, prescribed burns, or treatment with steam.
Bauer C. 2013. Baylisascariosis–infections of animals and humans with unusual roundworms. Vet Parasitol. 193(4):404-12.
Hernandez SM, Galbreath B, Riddle DF, Moore AP, Palamar MB, Levy MG, DePerno CS, Correa MT, Yabsley MJ. 2013. Baylisascaris procyonis in raccoons (Procyon lotor) from North Carolina and current status of the parasite in the USA. Parasitol Res. 112(2):693-8.
Bowman DD, Ulrich MA, Gregory DE, Neumann NR, Legg W, Stansfield D. 2005. Treatment of Baylisascaris procyonis infections in dogs with milbemycin oxime. Vet Parasitol. 129(3-4):285-90.
CAPC Recommends
To avoid contamination with eggs of B. procyonis, raccoons should not be kept as pets and people and dogs should avoid areas frequented by raccoons.
Dogs should be maintained on monthly intestinal parasite control products with efficacy against ascarids to treat potential newly acquired infections.
Keeping dogs confined to a leash or in a fenced yard will limit the opportunity for dogs to acquire infection with Baylisascaris spp.
Canine
Baylisascaris procyonis is an ascarid of raccoons that is occasionally found in dogs.
Other Baylisascaris spp. are present in wildlife hosts but have not yet been detected in dogs.
Dogs become infected with Baylisascaris procyonis via ingestion of larvated eggs from a contaminated environment or ingestion of paratenic hosts that have consumed larvated eggs and thus have larvae in their tissues.
After ingestion of infective eggs, larvae of B. procyonis, like those of other ascarids, migrate through the abdominal organs and the musculature. However, larvae of B. procyonis also have a propensity to invade the central nervous system, resulting in neurologic disease.
Baylisascaris procyonis egg on left, T. canis on right
Nonembryonated B. procyonis eggs may be passed in the feces of an infected dog.
Adult ascarids in the small intestine of the infected dog are grossly similar to Toxocara and Tocascaris spp. They are large stout worms with three lips on the anterior end. Unlike the other ascarids that can infect dogs, Baylisascaris spp. do not have salient cervical alae.
Infections with adult B. procyonis have not been commonly associated with clinical disease in dogs. However, treatment is still warranted, particularly in light of the severe zoonotic disease associated with this ascarid.
Although uncommon, there are reports of neurologic disease in dogs attributed to B. procyonis larvae migrating in the central nervous system.
Baylisascaris procyonis occurs in raccoons across the United States and Canada. High prevalence rates have been reported in the midwestern, northeastern, and western states but isolated areas in Texas, Florida, and Appalachia can have prevalence. In some studies, up to 90% of adult raccoons from a given geographic region were found to be infected with B. procyonis.
Historically this parasite was absent in the southeastern United States, but recent reports have also documented this parasite in raccoons in parts of Georgia, Florida, and North Carolina, suggesting that the range of this parasite may be expanding or that it may occur in localized populations in some areas.
Although comprehensive surveys to determine the prevalence of B. procyonis in dogs are lacking, more than two dozen cases of confirmed canine infection with adult raccoon ascarids have been reported, primarily from the midwestern United States.
Because of the serious zoonotic threat posed by this species, veterinarians and technicians should properly diagnose intestinal Baylisascaris sp. infections in dogs and make sure they receive appropriate treatment.
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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:
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.
Pancreatitis in Dogs
Most commonly called “raccoon disease” because of its prevalence in the raccoon population, baylisascariasis comes from contact with raccoon feces, and from ingesting animal tissue that is infected with the Baylisascaris procyonis parasite.
Commonly referred to as roundworm, the B. procyonis larvae is found in a large part of the animal population, including humans — making this a zoonotic disease, which means that it can be spread from an infected animal to other animal species, which includes humans. Raccoons are the optimal carriers of this worm, since the health of the raccoon is not adversely affected, making it the ideal host and disseminator of the parasite. The B. procyonis larvae is typically spread through the fecal material into the environment. Any contact with the feces, or with soil that has been used by an infected raccoon, may lead to systemic infection. Therefore, it is essential to practice methods of avoidance and caution in areas where raccoons are prevalent.
Intermediate carriers are birds, rabbits and rodents, amongst other animals. The larva is known to migrate to the brain, where it affects the nervous system. In this weakened state, the small animal becomes an easy catch, and the larva is ingested when the predator animal (i.e., a dog) ingests tissue from the infected animal. This is another way in which the worm is disseminated to other animals.
This disease is known to occur throughout the United States, with reported outbreaks in zoos and on farms. However, an outbreak can occur wherever animals are kept together in large groups.
While this infection can often be treated in adult dogs, it is almost always fatal for puppies. In addition, because the worm sometimes attacks the brain and nervous system, this infection may be mistaken for rabies. If rabies is suspected, you may wish to ask your veterinarian to test for the presence of the B. procyonis.
The condition or disease described in this medical article can affect both dogs and cats. If you would like to learn more about how this disease affects cats, please visit this page in the PetMD health library.
Two types of baylisascariasis have been reported in dogs: intestinal infection and visceral disease. The development of the roundworm begins with ingestion of the roundworm eggs. They then migrate to the intestines, where they further develop before their final migration into the viscera (the organs that occupy the abdominal cavities), the nervous system, or the eye. These types of infections are referred to, respectively, as larval migrans; visceral larval migrans (VLM); neural larval migrans (NLM); and ocular larval migrans (OLM).
The intestinal form is most commonly found in adult dogs, while infection of internal organs, particularly the brain and spinal cord (visceral disease) is more common in puppies. Often, there are not any outward symptoms associated with early onset of the disease, but occasionally dogs will show signs of neurological disease due to the worm attacking the nervous system. Signs of neurological disease (NLM) include:
Infection of the viscera (VLM) may present symptoms of liver and/or lung disease, while infection of the eye (OLM) may not be apparent until your dog has lost the use of its vision.
The most common method of acquiring the infection originates from sharing an area with infected raccoons. A dog can become infected with the disease from coming into contact with raccoon feces, from ingestion of B. procyonis eggs, which may remain viable in the soil long after the raccoon feces has disintegrated or been removed, from ingestion of animal tissue that is infected with the roundworm (e.g., rabbits, birds, etc.), or from close contact with other infected animals.
You will need to give your veterinarian a thorough history of your dogs health, including a background history of symptoms, and possible incidents that might have led to this condition. The history you provide may give your veterinarian clues as to which organs are being affected. Knowing the path the parasite has taken is essential for treating the infection appropriately.
The intestinal form of baylisascariasis is found by examining the dogs feces, while the larval form may be found in association with other diseases such as rabies, canine distemper, and congenital neurological defects. A direct fecal smear test will detect the intestinal form of the disease, while the larval form can usually be found through an eye (ophthalmoscopic) examination, or by a laboratory examination of a tissue sample.
If your dog tests positive for this parasite, there are several medications that can be administered.
A follow-up visit is recommended two weeks after the initial treatment, in order to analyze the feces for worms, and then again after a month to check for the intestinal form of the disease. This is a zoonotic disease, so it is transmissible to humans and other animals, with children being at the highest risk of acquiring the infection and of suffering the worst effects. Accidental ingestion of roundworm eggs can cause serious disease in humans. Ingestion may occur as a result of playing in sand that has been used by raccoons or other infected animals, from contact with soil that is infected with the eggs, or from contact with infected feces (during the course of cleaning it up). It is essential to be especially cautious until you have been assured that your dog has entirely recovered from the infection and is no longer shedding the eggs through its feces. Disposable gloves should be worn when handling your dogs waste materials, and hygiene regarding the hands and nails will need to be a priority if you live in an area that is occupied by raccoons.
The location where your dog contracted the roundworm should be well observed and monitored, and neighbors should be notified of the risk to their own pets.
The most important preventative step is to keep pets away from areas with raccoons and to prevent pets from ingesting animal tissue. Other steps that can be taken to protect your family and pet from this parasite are to keep sand boxes covered, check your property for raccoon droppings and deceased animals, and make sure that your dog or puppy has been dewormed.
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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.