RESUMO
One hundred faecal specimens and corresponding blood samples were evaluated for Haemonchus contortus infection in sheep by ELISA utilizing somatic, circulating and copro-antigens. Results proved that coproantigen was more potent than the others in diagnosis of sheep haemonchosis. SDS-poly-acrylamide gel electrophoresis demonstrated that the three antigens are structurally related. Immunoblot analysis revealed that somatic antigen contained 6 polypeptides of molecular weights 234, 205, 178, 83, 48 and 14 kDa, while, coproantigen showed 4 immunogenic polypeptides of 234, 205, 85 and 45 kDa. In circulating antigen only 2 polypeptides of molecular weights 165 and 99 kDa were immunoreactive. The potency of coproantigen may be attributed partially to one polypeptide of molecular weight 45 kDa. This low molecular weight polypeptide was only expressed in coproantigen as an immunogen, probably increases the immunogenicity, and may have potential diagnostic and protective values