The effect of route of administration of a Babesia divergens inactivated vaccine on protection against homologous challenge.

Two groups of 5 adult cows were immunized with a concentrated lysate of blood from a splenectomized calf infected with Babesia divergens with a parasitaemia of 20 per cent. The lysate was administered in 2 doses with a 14-day interval between them; it was injected subcutaneously to one group and intravenously to the other. Nineteen days after the second inoculation, both groups plus a third group of similar cows which acted as controls were infected subcutaneously with blood containing 10(9) B. divergens of the same strain, and clinical and haematological variables were monitored closely for 3 weeks. Both pretreated groups were much less seriously affected than the controls, with the group inoculated subcutaneously showing the least effects due to the challenge infection. It was concluded that protection could be induced against infections of B. divergens by injection of inactivated parasites of the same strain, and that subcutaneous inoculation was preferable to intravenous.