Immune response of sheep to Haemonchus contortus: serum antibodies against cross reacting antigens between parasites.

Normal and H. contortus infected sera were studied by ELISA technique against different stages of the parasites. In all cases antibody activity was detected. This activity in serum is partially eliminated after absorption with an adult worm extract of N brasiliensis. N. brasiliensis and H. contortus antigens were analysed by TCIEP with a rabbit anti-N. brasiliensis serum to examine shared antigens of H. contortus. A minimum of seven cross reacting antigens were detected. H. contortus adult worm extract was absorbed by the rabbit anti-N. brasiliensis serum. After absorption all cross reacting antigens were removed but at least one antigen reacting with a rabbit serum anti-H. Contortus is maintained. When this antigen is tested in elisa technique only a weak antibody activity is found in normal serum.