Nuclear techniques in Babesiosis and Anaplasmosis

The use of γ-irradiation to produce stable avirulent strains of four Babesia species, B. bovis, B. bigemina, B. divergens and B. major, is described. Field trials indicate that, for B. divergens, this procedure produces a highly protective live vaccine. 0.35 kGy (35 krad) is the optimum radiation dose to produce stable avirulent B. bovis organisms which induce protective immunity for a minimum period of 12 months. These organisms are non-transmissible by the tick vector and do not revert to virulence after 12 months in a carrier animal. The development of highly sensitive radioimmunoassays specific for B. bovis is described. These tests can detect as little as 2 ng anti-Babesia antibody per mL of sera, and are more accurate than existing serological assays. Less effort has been made to vaccinate animals against Anaplasma using irradiated organisms or to develop sensitive serological diagnostic tests. However, some studies indicate that exposure to doses of about 0.9 kGy results in organisms which are attenuated in terms of their pathogenic effect and which induce strong levels of resistance to challenge with virulent organisms. The present constraint in developing RIA techniques for detection of Anaplasma antibodies lies in the high degree of non-specific cross-reactivity between Babesia and Anaplasma antigens and antisera. (author)