Studies on the immune response of sheep to Chabertia ovina (Fabricius, 1788)

The immunological basis of host resistance to C. ovina was established by the demonstration of a marked anamnestic response by 6 sheep to a second infection of C. ovina after previous sensitization. Reaginic antibody was detected in the circulation of 20 sheep tested during both primary and secondary infection. It was first detected 5 weeks after infection with 2000 larvae, 8 weeks after infection with 1000 larvae and 12 weeks after infection with 400 larvae. In contrast, precipitating antibody was detected in only 10 per cent of sheep tested, while in vivo and in vitro tests for delayed hypersensitivity were negative. Studies on the effect of antilymphocytic serum on immunity to C. ovina suggested that the development of resistance to C. ovina requires the participation of the thymus-derived lymphocyte.