The development of antibody to Cowdria ruminantium in mice and its role in heartwater disease.

DBA/2 and Balb/c mice were used as a model to study the immune responses to Cowdria ruminantium. Both strains of mice were inoculated with 1, 10 or 100 LD50 of the Crystal Springs strain of C. ruminantium. Antibody to C. ruminantium started to develop in the second week post-inoculation and the titre of the antibody was dependent on the inoculation dose of C. ruminantium. The possible role of antibody in heartwater disease was studied by in vitro neutralization assays using both mouse sera and bovine sera. Results of these tests show that hyperimmune serum from both DBA/2 and Balb/c mice had the ability to neutralize infection in vitro, with the DBA/2 serum showing a greater neutralizing effect. Two bovine sera, one from a laboratory infected animal and one a pool from two animals infected in the field also gave a neutralizing effect.