Visceral larva migrans

Alternative names:

toxocariasis

Definition:

A disease mostly of children that results from infection of the child by worms that are normally gastrointestinal parasites of dogs or cats.

Causes, incidence, and risk factors:

The dog and cat worms are Toxocara canis and Toxocara cati respectively (other species of Toxocara can cause infection). These worms inhabit the intestinal tract of dogs and cats. Their eggs appear in abundance in the feces of these animals. When children ingest eggs from contaminated vegetation, dirt, or stool itself, the eggs hatch into larvae in the intestinal tract. They burrow through the intestinal wall where they then migrate to other organs of the body, most commonly the liver and lung but also the brain, eye, and other organs.

A human is not a true host for the Toxocara parasite, and subsequently the larvae do not develop past the larval stage. However, in their migration through the tissues they cause inflammation and tissue damage. Children develop fever, lung problems including cough and wheezing, seizures, occasionally hive-like rashes. Larva migrating into the structures of the eye may cause decreased visual acuity, swelling around the eye (periorbital edema), and crossed eyes (strabismus). The disease is generally self-limiting and symptoms abates over a period of months. Often symptoms are mild enough that treatment is not instituted. A specific and time proven drug is not available.