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 and were carefully treated to allow the parasites to remain in the dogs' bodies for long enough to evoke an immune response. Once recovered from the initial infections, both dogs received 2 separate homologous challenges with live parasites. During the second challenge, neither dog showed clinical signs of disease. An experimental vaccine was developed against the isolated B. canis strain by growing parasites in a micro-aerophilous stationary phase cell culture system to provide (a) antigen-containing supernatant material and (b) pellet material containing dead parasites. Two dogs each were inoculated with the different formulations of the vaccine on 2 separate occasions. Three weeks after the second inoculation, all 4 dogs were challenged with live parasites. Three of the 4 dogs recovered from the challenge without any anti-babesial treatment.