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Toxocara Infection (toxocariasis) and Animals

What is toxocariasis?

Toxocariasis (TOX-o-kah-RYE-uh-sis) (also known as toxocaral larva migrans, visceral larva migrans, ocular larva migrans, and covert toxocariasis) is an infection caused by parasitic roundworms found in the intestines of dogs (Toxocara canis) and cats (T. cati). Symptoms in humans may be produced by the presence of the larval worms migrating in parts of the body. Toxocara infections can cause ocular larva migrans (OLM), an eye disease that 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.

toxocara egg

Toxocara egg

Heavier, or repeated Toxocara infections, while rare, can cause visceral larva migrans (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. 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.

Can animals transmit toxocariasis to me?

Yes, but usually through the environment. The infection is common in dogs and cats, puppies and kittens can get the infection from the mother before birth or from her milk. The immature worms (larvae) mature rapidly in the puppy's or kitten's intestines; the worms may begin to produce large numbers of eggs that contaminate the environment through the animal's stool. Eggs soon develop into infective larvae, and humans can become infected after ingesting infective Toxocara eggs in soil or other contaminated surfaces.

How do I protect myself from getting 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.

How can I find out more about toxocariasis?

Learn more about toxocariasis at CDC's Parasitic Diseases site.

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