Specificity and sensitivity of skin test reactions to extracts of Toxocara canis and Ascaris suum II. Homologous 48-hour passive cutaneous anaphylaxis tests with sera from 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 a modified passive cutaneous anaphylaxis procedure in guinea pigs. Pooled sera from animals infected with low doses (0.01, 0.1, or 1.0 egg/g) were most reactive with the homologous larval antigen preparation. However, the Toxocara antisera were highly reactive with this antigen only, whereas the Ascaris antisera reactions could not be interpreted as being clearly positive with any of the antigen preparations. Sera from hyperinfected animals were also reactive with the homologous larval antigen. In addition, Ascaris larval antigen was reactive with Toxocara antiserum. The reciprocal relationship, i.e., reactivity of Toxocara larval antigen with Ascaris antiserum, was no apparent. In no instance did adult antigens induce reactions that could be interpreted as specific or sensitive indicators of antibody.