Toxocaridae

Toxocaridae is a family of parasitic nematodes that infect canids and felids and which can cause visceral larval migrans in humans. In humans, the worms cannot reproduce.

Three important species include:
 * Toxocara canis, which infects dogs,
 * Toxocara cati, which infects cats and which lacks intermediate hosts,
 * Toxocara vitulorum, which infects buffalo and cattle.

Infection
Infection by Toxocara canis or cati can cause different clinical manifestations. One of the clinical manifestations is Visceral larval migrans. In this condition, the larvae are unable to develop in humans like they do in cats and dogs, their natural host. No development leaves the larvae to aimlessly wander in the body causing inflammation. The most commonly infected sites include liver and lungs. Eggs are introduced to the body through ingestion. Oral ingestion can occur after eating with egg-infected hands after handling infected dogs or cats. result in egg injestion due to eating after egg deposition on the hands and face. In children without exposure to animals, eggs can be introduced by directly ingesting egg-contaminated soil while a child plays in a yard or playground. Usually the scenario is of a young child with a new puppy and unfortunately many young children who have been infected with these larvae, which form granulomas in the eye, have been misdiagnosed to have retinoblastoma and have had their eyes erroneously removed (enucleation).

Diagnosis
Direct identification of larvae in human disease is not feasible, so the diagnosis relies on history supported by serologic ELISA assay. The most sensitive assay, called E/S (excretory/secretory), contains 96 immunogenic antigens isolated from cultured T. canis larvae.