COMPARISON OF 2 ENZYME IMMUNOASSAYS FOR THE DETECTION OF HAEMONCHUS-CONTORTUS INFECTIONS IN SHEEP

Two enzyme-linked immunosorbent assays (ELISA) using either excretory/ secretory (ES) products or crude somatic antigens (CSA) of adult Haemo nchus contortus were compared for their ability to detect antibodies a gainst H. contortus in sheep. Serum samples obtained from a group of 3 2 H. contortus mono-infected sheep were tested in the two ELISAs and t he obtained data were compared with the results of the faecal examinat ions of these sheep. The first sheep became patent 3 weeks post infect ion (p.i.) and all sheep had positive egg counts at week 5 p.i. The fi rst antibodies against H. contortus were detected 1 week p.i. and all sheep were found positive by both ELISAs at week 4 p.i. Using sera fro m a large number of H. contortus-infected sheep a difference in sensit ivity between the ES ELISA (97.7%) and the CSA ELISA (89.2%) was found . The specificity of each assay was determined by testing sera obtaine d from sheep with mono-infections of H. contortus tus, Trichostrongylu s colubriformis, Trichostrongylus vitrinus, Ostertagia circumcincta, N ematodirus battus, Cooperia curticei, Fasciola hepatica, Taenia ovis o r Eimeria spp. The specificity of the ES ELISA was 87.2%, whereas the specificity of the CSA ELISA was 82.7%.