IMMUNE-RESPONSES TO SOUTH-AFRICAN BABESIA-CANIS AND THE DEVELOPMENT OF A PRELIMINARY VACCINE

The immune responses of 2 Beagles to live parasites of an isolated B. canis strain were tested. The dogs were infected with live parasites a nd were carefully treated to allow the parasites to remain in the dogs bodies for long enough to evoke an immune response. Once recovered fr om the initial infections, both dogs received 2 separate homologous ch allenges with live parasites. During the second challenge, neither dog showed clinical signs of disease. An experimental vaccine was develop ed against the isolated B. canis strain by growing parasites in a micr o-aerophilous stationary phase cell culture system to provide (a) anti gen-containing supernatant material and (b) pellet material containing dead parasites. Two dogs each were inoculated with the different form ulations of the vaccine on 2 separate occasions. Three weeks after the second inoculation, all 4 dogs were challenged with live parasites. T hree of the 4 dogs recovered from the challenge without any anti-babes ial treatment.