Specificity and sensitivity of skin test reactions to extracts of Toxocara canis and Ascaris suum. I. Skin tests done on infected guinea pigs.

The specificity and sensitivity of adult and larval somatic antigens, and perienteric fluid of Toxocara canis and Ascaris suum were investigated by using intradermal skin tests in guinea pigs. These animals were infected with low doses (0.01, 0.1 or 1.0 egg/g) of these helminths. Toxocara larval antigen (TL) induced larger reactions in Toxocara-infected animals than did the other antigens, suggesting a superior sensitivity for this antigen. In addition, Ascaris perienteric fluid (AP) provoked skin responses in these animals of a magnitude similar to those induced by TL. The reciprocal relationship, i.e., comparable reactivity of AP and TL in Ascaris-infected animals, was not apparent. In general, Ascaris larval antigen and AP elicited larger intradermal reactions than other antigens in Ascaris-infected animals. The results of this study indicated no superiority of adult antigens in differentiating Ascaris and Toxocara infections.