Roundworm Infection (Zoonotic)
What is toxocariasis?
Toxocariasis is a zoonotic (animal to human) infection caused by the parasitic roundworms commonly found in the intestine of dogs (Toxocara canis) and cats (T. cati).
What are the symptoms of toxocariasis?
There are two major forms of toxocariasis:
1) Ocular larva migrans (OLM):
Toxocara infections can cause OLM, an eye disease that can cause blindness. OLM occurs when a microscopic worm enters the eye; it may cause inflammation and formation of a scar on the retina. Each year more than 700 people infected with Toxocara experience permanent partial loss of vision.
2) Visceral larva migrans (VLM):
Heavier, or repeated Toxocara infections, while rare, can cause VLM, a disease that causes swelling of the body’s organs or central nervous system. Symptoms of VLM, which are caused by the movement of the worms through the body, include fever, coughing, asthma, or pneumonia.
How serious is infection with Toxocara?
In most cases, Toxocara infections are not serious, and many people, especially adults infected by a small number of larvae (immature worms), may not notice any symptoms. The most severe cases are rare, but are more likely to occur in young children, who often play in dirt, or eat dirt (pica) contaminated by dog or cat stool.
How is toxocariasis spread?
The most common Toxocara parasite of concern to humans is T. canis, which puppies usually contract from the mother before birth or from her milk. The larvae mature rapidly in the puppy’s intestines; when the pup is 3 or 4 weeks old, they begin to produce large numbers of eggs that contaminate the environment through the animal’s stool. The eggs soon develop into infective larvae.
How can I get toxocariasis?
You or your children can become infected after accidentally ingesting (swallowing) infective Toxocara eggs in soil or other contaminated surfaces.
What should I do if I think I have toxocariasis?
See your health care provider to discuss the possibility of infection and, if necessary, to be examined. A blood test is available for diagnosis.
What is the treatment for toxocariasis?
VLM is treated with antiparasitic drugs, usually in combination with anti-inflammatory medications. Treatment of OLM is more difficult and usually consists of measures to prevent progressive damage to the eye.
Who is at risk for toxocariasis?
Young children; owners of dogs and cats.
How can you prevent toxocariasis?
- Have your veterinarian treat your dogs and cats, especially young animals, regularly for worms.
- Wash your hands well with soap and water after playing with your pets and after outdoor activities, especially before you eat. Teach children to always wash their hands after playing with dogs and cats and after playing outdoors.
- Do not allow children to play in areas that are soiled with pet or other animal stool.
- Clean your pet’s living area at least once a week. Feces should be either buried or bagged and disposed of in the trash.
- Teach children that it is dangerous to eat dirt or soil.
For more information:
- Glickman LT, Schantz PM. Epidemiology and pathogenesis of zoonotic toxocariasis. Epidemiol Rev 1981;3:230-50.
- Kazacos KR. Visceral and ocular larva migrans. Semin Vet Med Surg (Small Anim) 1991;6:227-35.
- Schantz PM. Toxocara larva migrans now. Am J Trop Med Hyg 1989;41(3) Suppl:21-34.
*This information prepared in association with the American Association of Veterinary Parasitologists (AAVP).
This fact sheet is for information only and is not meant to be used for self-diagnosis or as a substitute for consultation with a health care provider. If you have any questions about the disease described above or think that you may have a parasitic infection, consult a health care provider.