Listed Disease

Bovine babesiosis

Bovine babesiosis is a tick-borne disease of cattle caused by protozoan parasites of the genus Babesia, order Piroplasmida, phylum Apicomplexa, and including Babesia bovis, B. bigemina and B. divergens. Rhipicephalus (Boophilus) microplus, the principal vector of B. bovis and B. bigemina, is widespread in tropical and subtropical countries. The major vector of B. divergens is Ixodes ricinus. Babesia bovis is generally more pathogenic than B. bigemina or B. divergens. Babesia bovis infections are characterised by high fever, ataxia, anorexia, general circulatory shock, and sometimes nervous signs as a result of sequestration of infected erythrocytes in cerebral capillaries. Anaemia and haemoglobinuria may appear later in the course of the disease. In acute cases, the maximum parasitaemia (percentage of infected erythrocytes) in circulating blood is less than 1%. This is in contrast to B. bigemina infections where the parasitaemia often exceeds 10% and may be as high as 30%. In B. bigemina infections, the major signs include fever, haemoglobinuria and anaemia. The parasitaemia and clinical appearance of B. divergens infections are somewhat similar to B. bigemina infections. Vaccines consisting of live, attenuated strains of B. bovis, B. bigemina or B. divergens are produced in several countries either from the blood of infected donor animals or by in-vitro culture. Babesia bovis and B. bigemina vaccines are not infective for humans. However, cases of B. divergens have been reported in splenectomised individuals.