Baylisascaris Infection

What is Baylisascaris Infection

Baylisascaris infection in humans is rare, but it can happen if you accidentally swallow (ingest) something that has had contact (has been contaminated) with the roundworm eggs.

Baylisascarisis a type of roundworm that lives in the digestive system of certain wild animals. One species of the roundworm (Baylisascaris procyonis) is commonly found in raccoons, who shed the roundworm eggs in their feces.

When roundworm eggs are ingested, they hatch in the intestine. Then they may travel to other parts of the body (larva migrans syndrome), such as the liver, eyes, spinal cord, brain, or other organs. Infection can sometimes result in serious illness, and it must be treated as soon as possible.

What are the causes?

This condition is caused by ingesting Baylisascaris procyonisroundworm eggs. This can happen if you have contact with contaminated:

  • Soil.
  • Water.
  • Objects in areas that are frequently visited by raccoons.

What increases the risk?

The following factors may make you more likely to develop this condition:

  • Being a child. Young children are more likely to put contaminated soil or objects in their mouths.
  • Having a job that requires you to come in contact with raccoons. This can include wildlife handlers, trappers, hunters, or taxidermists.
  • Keeping a raccoon as a pet.
  • Living close to areas where raccoons live or spend time.

What are the signs or symptoms?

Symptoms may vary depending on how many eggs are ingested and where the larvae travel when they hatch. If you ingested a small amount of eggs, you may have few symptoms or no symptoms. If you ingested a large number of eggs, you could develop serious symptoms. Symptoms of infection may not develop until 1–4 weeks after ingestion. Symptoms of this condition may include:

  • Nausea.
  • Fatigue.
  • Enlargement of the liver.
  • Clumsiness or lack of coordination.
  • Difficulty paying attention.
  • Loss of muscle control.
  • Chest pain.
  • Coughing.
  • Blindness.
  • Eye swelling.
  • Sensitivity to light.
  • Coma.

How is this diagnosed?

This condition may be diagnosed based on your symptoms and whether you have been exposed to raccoons. You may have tests and procedures, such as:

  • MRI to check whether the infection has spread to the brain.
  • Blood tests.
  • Removing and testing a sample of the fluid in the spinal cord (lumbar puncture).
  • Removing a small piece of tissue (biopsy) and checking it under a microscope to see whether the infection has spread.
  • Eye exams to check for damage (lesions) from hatched larvae that may have traveled to the eye.

How is this treated?

This condition is treated with medicines, including:

  • Medicine to kill the roundworm larvae (anthelmintic medicine).
  • Medicine to help reduce inflammation (corticosteroids).

Treatment is most effective when it is started immediately. Depending on how severe the condition is, treatment may need to be done in a hospital. Treatment may last for several weeks.

Follow these instructions at home:

  • Take over-the-counter and prescription medicines only as told by your health care provider.
  • Keep all follow-up visits as told by your health care provider. This is important. In some cases, extended treatment with the anthelmintic medicine may require follow-up tests to check blood cell counts and liver function.

How is this prevented?

  • Do notfeed raccoons or other wild animals.
  • Do notkeep raccoons or other wild animals as pets.
  • Have a wildlife professional remove any raccoons that live near your home.
  • If you find raccoon feces around your house, contact a wildlife professional or animal control office to remove it. If you decide to remove the feces yourself, follow these instructions:
    • Wear disposable gloves and protective clothing, such as rubber boots or disposable booties.
    • Wear a respirator to prevent accidental ingestion of eggs if the feces are in a confined space, such as an attic.
    • Do notstir up dust and debris around the feces. If necessary, lightly spray the area with water to prevent dust.
    • Burn or bury any feces and contaminated material.
    • Treat contaminated decks and patios with boiling water or a propane torch. Talk with your local fire department before using any type of torch.
  • Keep young children away from raccoons, and do notlet them play in areas where raccoons are often found.
  • Discourage raccoons from living around your home. You can do this by:
    • Keeping trash cans closed.
    • Bringing all food inside.
    • Clearing away branches, twigs, and dense bushes (brush). This will discourage raccoons from making a den.
    • Keeping sandboxes covered when not in use to avoid feces.
    • Closing access to attics and basements.
    • Eliminating water sources, including fish ponds.

After being outside:

  • Wash your hands with soap and water.
  • Clean your clothes with hot water and detergent.

Contact a health care provider if:

  • You may have had contact with raccoon feces. If this is the case, contact a health care provider even if you do not have symptoms of baylisascaris infection.

Get help right away if:

  • You have symptoms of this infection and you may have been exposed to a raccoon.


  • Baylisascarisis a type of roundworm that lives in the digestive system of certain wild animals. You are most likely to get this infection from a raccoon.
  • This condition is caused by swallowing (ingestingBaylisascaris procyonisroundworm eggs. This can happen if you come into contact with contaminated soil, water, or objects that are left in an area with wild animals.
  • Symptoms may vary depending on how many eggs are ingested and where the larvae travel when they hatch. Symptoms can include nausea, fatigue, clumsiness, loss of muscle control, chest pain, coughing, blindness, and coma.
  • This condition is treated with medicines to kill the roundworm larvae (anthelmintic medicine) and reduce swelling (corticosteroids).
  • You can prevent this condition by avoiding contact with raccoons, washing your hands after playing or gardening outside, and calling a wildlife professional to remove any raccoons or raccoon feces.

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