Chemoprophylaxis with diminazene aceturate in experimental Babesia bigemina infection in cattle.

Four-month-old fully susceptible cross bred calves were immunised against Babesia bigemina infection by treating them, during the prepatent period, with one or two doses of diminazene aceturate at 3 mg (kg bodyweight)-1. After 45 days the recovered calves were challenged with the homologous strain of B bigemina infected blood. The ensuing host responses, body temperature, parasitaemia, haemoglobin, packed cell volume, haemoglobinuria, capillary agglutinating antibodies and mortality, were studied. The four untreated control calves developed a severe form of the disease with classical symptoms and two died. Calves of both groups which recovered resisted the challenge infection with a mild relapse in the immunised group, thus indicating a state of premunition. The effect of one dose of diminazene was sufficient to suppress all the clinical effects of the disease.