larva migrans, visceral

The parasitic roundworm Toxocara inhabits the gut of dogs and cats (Toxocara canis or Toxocara catii respectively). Pets often defecate into childrens sand boxes, which transfers the eggs into the sand. When the eggs of Toxacara are ingested by little humans (playing in sandboxes, for example), they hatch in the gut and move through the wall of the intestine and into the bloodstream. This is termed visceral larva migrans or toxocariasis. The larvae can enter the liver, the lung, brain or eye; eventually they die and become walled off in microscopic cysts and calcify, but not before causing tissue damage. In the eye, Toxocara cysts may be mistaken for retinoblastoma, cancer of the eye, leading to removal of an eye. The eosinophils (white cells involved with allergy and defense against parasites) may be enormously elevated (eosinophilia).

Symptoms of infection range from none, if the infection is light, to a variety of signs including fever, cough, wheezing, seizures, rashes, lymph node enlargement, and visual symptoms including decreased vision.

Remember to keep your small child's play sand covered when the sandbox is not in use! Wash you hands after handling pets, and keep puppies and kittens dewormed. See larva migrans, cutaneous ("creeping eruption").