Toxocariasis (TOK-so-ka-RY-a-sis) is an infection in people caused by parasitic roundworms found in the intestines of cats and dogs. It most commonly affects young children who come in contact with contaminated dirt.


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Toxocara canis

Toxocara catis

Many cats and dogs, especially kittens and puppies, have intestinal worms called Toxocara canis (in dogs) or Toxocara cati (in cats). Eggs from Toxocara pass with the stools from infected cats and dogs and then contaminate the soil.

When children play in contaminated areas, the eggs can stick to their hands or toys and then be swallowed. When the eggs enter the digestive system, they hatch. The larvae * burrow through the intestinal wall and move to the liver, lung, and sometimes to other sites, including the central nervous system, eye, kidney, and heart. The larvae may stay alive for many months and cause damage to tissues or organs. Because the larvae are cat or dog parasites, they do not complete their life cycle in humans.

* larvae are worms at an intermediate stage of the life cycle between eggs and adulthood.

* lymph nodes are round masses of tissue that contain immune cells whose job it is to filter out harmful microorganisms; lymph nodes can become enlarged during infection.

What Happens When People Have Toxocariasis?


Most people with toxocariasis have no symptoms. If symptoms occur, they may include fever, cough or wheezing, and seizures. Other symptoms may include abdominal pain, enlarged liver or spleen, loss of appetite, rash, and enlarged lymph nodes * . Toxocariasis can also affect the eyes and cause decreased vision, swelling around the eyes, and a cross-eyed appearance.

Diagnosis and Treatment

Toxocariasis is diagnosed through a blood test. For most cases, no treatment is necessary. Certain medications that are effective against toxocariasis may be used to eliminate the infection.

How Can Toxocariasis Be Prevented?

As with other infections, good hygiene and frequent handwashing are essential. Important safety measures include:

  • Keeping children from playing in areas contaminated by cats and dogs.
  • Teaching children not to put their hands and toys in their mouths after playing with cats and dogs.
  • Teaching children to wash their hands thoroughly after playing outside, after playing with pets, and before eating.
  • Keeping pets away from sandboxes, which should be covered when not in use.

Pets should be checked for parasites periodically by veterinarians and treated if they are found to be infected.


The U.S. Centers for Disease Control and Prevention (CDC), 100 Clifton Road N.E., Atlanta, GA 30333. CDC's Division of Parasitic Diseases posts a fact sheet about toxocariasis at its website.
Telephone 404-639-3534

See also
Parasitic Diseases

Also read article about Toxocariasis from Wikipedia

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