 
Toxocariasis
(TOX-o-kah-RYE-us-sis)
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). In the United States, an estimated 10,000 cases of
Toxocara infections occur yearly in humans.
What are 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 from larvae 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.
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