Comparison of cestode antigens in an enzyme-linked immunosorbent assay for the diagnosis of Echinococcus granulosus, Taenia hydatigena and T ovis infections in sheep.

Nine antigens, prepared from somatic tissue, cyst fluids or produced during in vitro culture of Echinococcus granulosus, Taenia hydatigena, T ovis or T crassiceps were tested for their suitability for the diagnosis of larval cestode infections in sheep by the enzyme-linked immunosorbent assay (ELISA). The sensitivity and specificity of each of these antigens were assessed using sera from sheep experimentally infected with graded monospecific infections of E granulosus, T hydatigena or T ovis eggs and sera from naturally infected aged sheep. The ability of eight of the antigens to detect the antibody response to larval cestode infection was also compared over 12 months using sera from serial bleedings. Using the ELISA, all of the antigens were able to detect the presence of larval cestodes, even in sheep with only one or two cysts. Over 12 months, the antibody responses were not generally statistically related to the total number of cysts present in the animals. None of the antigens was able to detect specific infections only. The antigen with least non-specific background activity, which consistently detected the highest antibody titres in the sera of all infected animals was the secretion from T ovis worms cultured in vitro, and is, therefore, the antigen of choice for the detection of non-specific infections with larval cestodes in sheep.