Toxocariasis
Toxocariasis (visceral larva migrans) is infection caused by larvae of the parasitic roundworms Toxocara canis or Toxocara cati.
Toxocariasis occurs mainly in young children, who acquire Toxocara eggs through contact with soil contaminated by the feces of dogs and cats that carry the parasite. Children's sandboxes, where dogs and cats often defecate, pose a particular hazard for exposure to the eggs. Children frequently transfer the eggs from their hands to their mouth and may eat the contaminated sand. Occasionally, adults who eat clay become infected. After the eggs are swallowed, larvae hatch in the intestine. The larvae penetrate the intestinal wall and are spread through the bloodstream. Almost any tissue of the body may be involved, but the liver and lung are most commonly affected. The larvae can remain alive for many months, causing damage by migrating through tissues and stimulating inflammation.
Symptoms and Diagnosis
Symptoms may start within several weeks of ingestion of the eggs; fever, cough or wheezing, and liver enlargement are the most common. Some people have a skin rash, spleen enlargement, and recurring pneumonia. When larvae infect the eye, inflammation and decreased vision may result.
A doctor may suspect toxocariasis in a person who has an enlarged liver, inflammation of the lungs, a fever, and high levels of eosinophils (a type of white blood cell). The diagnosis is confirmed by identifying Toxocara antibodies in the blood. Rarely, a sample of liver tissue is obtained and examined (biopsy) for evidence of larvae or inflammation resulting from their presence.
Prevention and Treatment
To prevent toxocariasis, dogs and cats should be dewormed regularly, starting before they are 4 weeks old. Covering sandboxes when not in use prevents animals from defecating in them.
The effectiveness of treatment is uncertain. In people, toxocariasis usually goes away without treatment. For people with severe symptoms, diethylcarbamazine or mebendazole may be helpful. Corticosteroids are sometimes prescribed to control the symptoms of inflammation.
| 
