Live vaccines against bovine babesiosis.

Bovine babesiosis is an important tick-borne disease caused by Babesia bovis, B. bigemina and B. divergens. The first steps taken in the development of an effective vaccination strategy against bovine babesiosis followed the observations that animals, recovered from natural infection with Babesia were strongly protected against subsequent challenge. Further investigation indicated that the use of donor blood from recovered animals to infect recipient animals did not produce the severe form of the disease. The past century has seen a refinement of this original carrier-donor system to one using attenuated less virulent strains with standardized doses of known parasite concentration to ensure reliability. With the implementation of good manufacturing practices further changes were necessary in the production of these vaccines, such as freezing for long-term storage to allow sufficient time for pre-release safety and effectivity testing. Regardless of these improvements the vaccines are not without problems and breakdowns and breakthroughs occur from time to time. Despite considerable research efforts into the development of alternative more consumer friendly vaccines, none is immediately forthcoming and the live attenuated babesiosis vaccines are still used in many countries.