The specificity of nematode allergens in the diagnosis of human visceral larva migrans.

Extracts of nematodes have been used as skin test antigens in the diagnosis of nematode infections for many years. Ascaris lumbricoides and Toxocara canis are two nematodes commonly involved in human parasitism, the latter being associated with the clinical condition of Visceral Larva Migrans. In vitro and in vivo experiments reported in this paper confirm experimentally, as well as clinically, the existence of cross-reacting antigens between T. canis and Ascaris spp., and probably between T. canis and other nematodes. These cross-reactions compromise the usefulness of skin tests in the diagnosis of such parasitic infections.