Toxocariasis is an infection transmitted from animals to humans (zoonosis) caused by the parasitic roundworms commonly found in the intestine of dogs (Toxocara canis) and cats (T. cati).
Anyone can become infected with Toxocara. Young children and owners of dogs or cats have a higher chance of becoming infected.
Approximately 5% of the U.S. population has antibodies to Toxocara. This suggests that tens of millions of Americans may have been exposed to the Toxocara parasite.
Dogs and cats that are infected with Toxocara can shed Toxocara eggs in their feces. Adults and children can become infected by accidentally swallowing dirt that has been contaminated with dog or cat feces that contain infectious Toxocara eggs. Although it is rare, people can also become infected from eating undercooked meat containing Toxocara larvae.
Many people who are infected with Toxocara do not have symptoms and do not ever get sick. Some people may get sick from the infection and may develop the following:
- Ocular toxocariasis: Ocular toxocariasis occurs when Toxocara larvae migrate to the eye. Symptoms and signs of ocular toxocariasis include vision loss, eye inflammation or damage to the retina. Typically, only one eye is affected.
- Visceral toxocariasis: Visceral toxocariasis occurs when Toxocara larvae migrate to various body organs, such as the liver or central nervous system. Symptoms of visceral toxocariasis include fever, fatigue, coughing, wheezing, or abdominal pain.
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 feces.
The most common Toxocara parasite of concern to humans is T. canis, which puppies usually contract from their mother before birth or from her milk. The larvae mature rapidly in the puppy’s intestine; when the pup is 3 or 4 weeks old, the worms inside the puppy begin to produce large numbers of eggs that contaminate the environment through the puppy’s feces. After the eggs pass into the environment, it takes about 2 to 4 weeks for infective larvae to develop in the eggs. If a person ingests one of these infective eggs, then they can become infected with toxocariasis.
Toxocariasis is not spread by person-to-person contact like a cold or the flu.
See your health care provider to discuss the possibility of infection and, if necessary, to be examined. Your provider may take a sample of your blood for testing.
Visceral toxocariasis is treated with antiparasitic drugs. Treatment of ocular toxocariasis is more difficult and usually consists of measures to prevent progressive damage to the eye.
- Take your pets to the veterinarian to prevent infection with Toxocara. Your veterinarian can recommend a testing and treatment plan for deworming.
- Wash your hands with soap and water after playing with your pets or other animals, after outdoor activities, and before handling food or eating.
- Teach children the importance of washing hands to prevent infection.
- Do not allow children to play in areas that are soiled with pet or other animal feces.
- Clean your pet’s living area at least once a week. Feces should be either buried or bagged and disposed of in the trash. Wash your hands after handling pet waste.
- Teach children that it is dangerous to eat dirt or soil.
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