Immunity following use of Australian tick fever vaccine: a review of the evidence

Abstract

Objective To review the evidence available on the degree and duration of immunity provided by Australian tick fever vaccines against Babesia bovis, B bigeminaand Anaplasma marginale infections in Australia and overseas. Background Vaccines containing attenuated strains of B bovis and B bigemina as well as A centrale grown in splenectomised calves have been used in Australia since 1964 to immunise cattle against tick fever. About 800,000 doses of vaccine are supplied annually and much of the evidence for protection is field evidence rather than conventional immunological measures or pen trials. Conclusions Immunity to Babesia bovis and B bigemina – A single inoculation generally provides sound, long‐lasting protection both in Australia and overseas. No evidence was found of a loss of immunity with time. Vaccine failures to B bovis d o occur, but are uncommon and evidently caused by a number of factors, including immune responsiveness of the vaccinated animals, and immunogenicity of the vaccine strain. Immunity to Anaplasma marginale– The vaccine containing A centrale provides partial, variable protection against A marginale. Protection against challenge in Australia is adequate in most cases to prevent disease and use of the vaccine in this country appears to be justified. Protection against antigenically diverse, highly virulent stocks of A marginale i n other countries is, at times, clearly inadequate and better vaccines are required in situations where the challenge is severe.

Anaplasma marginale msp1 α Genotypes Evolved under Positive Selection Pressure but Are Not Markers for Geographic Isolates

“…Therefore, if cattle movement introduces a new A. marginale genotype, it could be established by mechanical and/or biological transmission to susceptible cattle. In regions with few introductions of A. marginale isolates such as Australia, genotypic variation was found to be minimal (3,19). In regions like Oklahoma, where the movement of cattle is extensive, a highly heterogeneous population of A. marginale isolates would be expected.…”

The current status of major tick borne diseases in Zambia

“…The latter is restricted to some commercial farms, but it is not common practice. The reported success of immunization using tick fever vaccines in Australia [12], Paraguay [13] and South Africa [21] represents a potential for the control of babesiosis and Anaplasmosis in Zambia. In these countries, Babesia strains have been shown to provide good protection against field challenge and were safe to use in highly susceptible cattle.…”

Attenuated vaccines for tropical theileriosis, babesiosis and heartwater: the continuing necessity

“…Protective immunity is unrelated to virulence of the vaccine strain and there is evidence that multiple passage of a strain might result in loss of immunogenicity [35]. Consequently, some vaccine strains become less immunogenic than others, and there is evidence that a combination of differing parasite populations is required for adequate protection.…”

“…From experience gained in Australia, immunity to B. bovis and B. bigemina persists for approximately four years [35]. Sterile immunity followed by chemosterilization in the case of B. bovis was more than three years, but cattle were fully susceptible to B. bigemina after 16 months [30].…”

“…Antigenic variation is thought to avoid strong protective responses mounted by the host [38]. Despite this immunological diversity, the Australian B. bovis and B. bigemina strains protect cattle in Africa, Latin America and Southeast Asia [35].…”