Comparison of three enzyme immunoassays for diagnosis of Dictyocaulus viviparus infection.

Three enzyme-linked immunosorbent assays (ELISA) that detect antibodies against Dictyocaulus viviparus in cattle were compared for sensitivity, specificity and seroconversion after primary infection. These assays were (i) an indirect ELISA with crude somatic antigens from adult D. viviparus (ca-ELISA), (ii) an indirect ELISA with purified antigens (sa-ELISA) isolated from somatic antigens of adult D. viviparus and (iii) a competition ELISA with antigen purified with anion chromatography in combination with monoclonal antibodies against D. viviparus. Sera from helminth-naïve calves and sera from calves monospecifically infected with Ostertagia ostertagi, Cooperia oncophora, Nematodirus helvetianus, Ascaris suum or Fasciola hepatica were used to determine the specificity of the assays. Sera from calves and milk cows experimentally or naturally infected with D. viviparus, and from vaccinated calves, were used to test the sensitivity of the assays and to determine when the ELISAs detected seroconversion. The specificity of the competition and the sa-ELISA was 97%, whereas the specificity of the ca-ELISA was 67%. The sensitivities of the sa-ELISA, the competition ELISA and the ca-ELISA were 97, 73 and 99%, respectively. All three assays detected seroconversion between 4 and 6 weeks after primary infection. None of the assays detected seroconversion in calves receiving lungworm vaccination. We conclude that of these three tests, the sa-ELISA can be used most beneficially to diagnose lungworm disease.