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Racoon Disease in Dogs

Baylisascariasis in Dogs

Baylisascariasis, often referred to as “raccoon disease,” is prevalent among raccoons and can affect dogs through contact with raccoon feces or by ingesting infected animal tissue. The disease is caused by the Baylisascaris procyonis parasite, commonly known as roundworm. This parasite can also infect humans, making it a zoonotic disease that can spread between different animal species.

Raccoons are the primary carriers of the B. procyonis larvae, as they remain unaffected by the parasite’s presence. The larvae are typically spread through raccoon feces into the environment. Any contact with contaminated feces or soil used by infected raccoons can lead to systemic infection. Therefore, precautions should be taken in areas where raccoons are prevalent.

Intermediate carriers of the parasite include birds, rabbits, and rodents. The larvae migrate to the brain, affecting the nervous system of the host animal. When a predator, such as a dog, ingests tissue from an infected animal, the larvae are ingested, further spreading the parasite.

Baylisascariasis has been reported throughout the United States, with outbreaks occurring in zoos and on farms. It can also occur wherever animals are kept in large groups.

While adult dogs can often be treated for the infection, it is almost always fatal for puppies. Additionally, since the parasite can affect the brain and nervous system, the infection may be mistaken for rabies. If rabies is suspected, veterinarians may test for the presence of B. procyonis.

Symptoms and Types

Baylisascariasis in dogs manifests in two forms: intestinal infection and visceral disease. The roundworm’s lifecycle commences with the ingestion of its eggs, followed by migration to the intestines for further development. Subsequently, the larvae migrate to various organs within the abdominal cavity, the nervous system, or the eye. These manifestations are termed larval migrans, namely: visceral larval migrans (VLM), neural larval migrans (NLM), and ocular larval migrans (OLM).

Intestinal infection primarily affects adult dogs, whereas visceral disease, particularly involving the brain and spinal cord, is more common in puppies. Initially, the disease may not exhibit noticeable symptoms, but in some cases, dogs may display signs of neurological issues due to the parasite’s impact on the nervous system. Symptoms of neurological disease (NLM) include unsteady walking, difficulty swallowing, lethargy, circling, seizures, and confusion.

Visceral disease (VLM) may manifest symptoms of liver and/or lung disease, while ocular larval migrans (OLM) might only become apparent once the dog experiences vision impairment.


The primary source of infection typically involves sharing an environment with raccoons carrying the disease. Dogs may contract the infection by encountering raccoon feces, ingesting B. procyonis eggs, which can persist in the soil even after the feces has decomposed or been cleared, consuming infected animal tissue such as rabbits or birds, or through close interaction with other infected animals.


To accurately diagnose baylisascariasis in your dog, it’s crucial to provide your veterinarian with a detailed account of your dog’s medical history, including any symptoms and potential incidents that could have led to the condition. This information will help your veterinarian identify which organs are affected and guide the appropriate treatment.

The intestinal form of baylisascariasis can be detected by examining the dog’s feces, while the larval form may be associated with other diseases such as rabies, canine distemper, and congenital neurological defects. A direct fecal smear test is typically used to identify the intestinal form of the disease, while the larval form may be detected through an eye examination (ophthalmoscopic) or by laboratory examination of a tissue sample.


If your dog is diagnosed with this parasite, several medications are available for treatment.

For the intestinal form:

  • Pyrantel Pamoate
  • Febantel
  • Praziquantel
  • Ivermectin
  • Mibemycin Oxime

For the larval form:

  • Corticosteroids
  • Long-term albendazole

Living and Management

After the initial treatment, it’s recommended to schedule a follow-up visit two weeks later to examine the feces for worms, followed by another visit after a month to monitor for the intestinal form of the disease. As this is a zoonotic disease, it can be transmitted to humans and other animals, with children being particularly vulnerable to severe effects. Accidental ingestion of roundworm eggs poses a significant risk to humans, which can occur through contact with contaminated soil or feces from infected animals.

It’s crucial to exercise caution until your dog has fully recovered and is no longer shedding eggs in its feces. When handling your dog’s waste, always use disposable gloves, and maintain proper hand and nail hygiene, especially in areas inhabited by raccoons.

Keep a close watch on the location where your dog contracted the roundworm, and inform neighbors about the potential risk to their pets.


Preventing exposure to areas inhabited by raccoons and avoiding ingestion of animal tissue are crucial steps in preventing this parasite. Additionally, covering sandboxes, regularly inspecting your property for raccoon droppings and deceased animals, and ensuring that your dog or puppy undergoes deworming are important measures to protect your family and pets from this parasite.

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