PATHOGENESIS: Toxocara canis is an intestinal roundworm parasite of dogs, wolves, foxes, and other canids. Human infestation with the second- or third-stage larvae of T. canis
is known as visceral larval migrans (VLM) (1).

Transmission of T. canisto human beings can occur by either ingestion of eggs in the contaminated soil or from contaminated hands or fomites. The eggs hatch in the small intestine, and the larvae then migrate into the mucosa to reach the portal circulation. They migrate to the liver, follow vascular channels to the lungs, and then enter the systemic circulation to reach numerous organs, most notably the liver, lung, brain, and eye. The larvae wander aimlessly through these various tissues but do not readily return to the intestine to develop into adult worms. Thus, their life cycle is not completed in humans. The wandering larvae, which can remain viable for many weeks or months in the tissues, characteristically promote an eosinophilic granulomatous response in various organs (1, 2).

1. Shields JA. Ocular toxocariasis. A review. Surv Ophthalmol 1984; 28:361-81.