Echinococcus granulosus, Taenia hydatigena, T. ovis:Evaluation of cyst fluids as antigen for serodiagnosis of larval cestodes in sheep

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Abstract
In order to monitor the progress of New Zealand's hydatids eradication campaign, a specific, serological, diagnostic test is required to identify infected sheep. An indirect haemagglutination test, using pyruvic aldehyde-stabilized sheep erythrocytes as the antigen carrier, was developed for the serodiagnosis of larval cestode infections of sheep. Using cyst fluid from Echinococcus granulosus, Taenia hydatigena and T. ovis as the antigens in this test, it was shown that the larval cestode species, responsible for an infection in sheep harbouring a single specific infection, could be identified by the higher titre given with the homologous antigen, in comparison to that given with the heterologous antigens. Sera of sheep infected with two or more species were also tested by this method, and the only specific infections to be diagnosed by differential titres were those due to the presence of live E. granulosus cysts. These antigens cannot be used for the diagnosis of specific larval cestode infections in the field because of the cross-reactivity between cyst fluids. However, the test did show that infection with larval cestodes could be diagnosed on a non-specific basis.