Babesia divergens in splenectomised rats.

Babesia divergens, from a bovine, was passaged through two gerbils before being injected into splenectomised rats. By repeated passage every three or four days through splenectomised rats higher parasitaemias were gradually obtained. By passage 28 parasitaemias of 60 per cent were recorded. In splenectomised rats the rat-adapted B divergens produced patent parasitaemias lasting seven to eight days after which no recrudescences were seen. Irradiation of splenectomised rats before infection exacerbated the infection. Anti-B divergens antibodies were detected in recovered rats and resistance to the parasite was passed from mother to offspring and in serum from recovered rats to naive splenectomised recipients.