An immunisation trial with in vitro produced Babesia bigemina exoantigens.

Bovine babesiosis, caused by Babesia bigemina, is an important tick-transmitted haemoprotozoan disease in the tropics. This study evaluated the immunoprotective efficacy of in vitro produced B. bigemina exoantigens in bovine calves. The calves inoculated with B. bigemina exoantigens did not show any clinical, parasitological or hypersensitivity reactions after inoculation. They withstood challenge without showing any clinical symptoms except a transient thermal reaction. In contrast, two out of four control calves exhibited clinical symptoms of babesiosis and one died. On challenge, there was a significant reduction in the haematological values of both groups. However, this was more pronounced in the control animals. Challenge resulted into a normocytic hypochromic anaemia. The vaccinated animals revealed a significant rise in antibody titres after vaccination as well as after challenge as detected by a single dilution ELISA. The rise in antibody titres of control animals was only moderate. Inoculation of B. bigemina exoantigens induced a protective immune response in the vaccinated animals which could protect them from infected blood challenge.