Babesia major in Britain: cross-immunity trials with Babesia divergens in splenectomised calves.

Splenectomised calves infected with Babesia major were shown to have no resistance to challenge with Babesia divergens; however, initial infection with B divergens provided a good protection against subsequent challenge with B major. It is suggested that this might mean that B divergens would be the dominant and most commonly encountered species in areas where both occur.