title: Studies on failure of T strain live Babesia bovis vaccine.
abstract: Field investigations of the protection afforded by the Australian live Babesia bovis vaccine used in the early 1990s (T strain) revealed inadequate vaccine-induced protection in certain herds. Vaccination/challenge trials using 207 experimental cattle were conducted to evaluate the protection afforded by T strain B bovis against field isolates from these herds. The trials investigated whether isolates that could 'break-through' T strain immunity were present in the field, the ability or inability of specific cattle to develop protective immunity after vaccination with T strain and the effect of attenuation and maintenance procedures on the immunogenicity of T strain. The results showed that B bovis parasites present early in the process of attenuation of T strain were more protective than those remaining late in the process. They also showed that cattle from properties experiencing vaccine failures were less protected by T strain vaccination than Bos taurus cattle randomly selected from the general population if vaccinated with highly attenuated T strain. A hypothesis is offered to explain these findings.
authors.affiliation: Tick Fever Research Centre, Wacol, Queensland.
authors.forename: R E
authors.initials: RE
authors.lastname: Bock
authors.forename: A J
authors.initials: AJ
authors.lastname: de Vos
authors.forename: A
authors.initials: A
authors.lastname: Lew
authors.forename: T G
authors.initials: TG
authors.lastname: Kingston
authors.forename: I R
authors.initials: IR
authors.lastname: Fraser
mesh_terms: D000818:Animals; D000913:Antibodies, Protozoan / Q000276:immunology; D016793:Babesia bovis / Q000145:classification / Q000276:immunology*; D001404:Babesiosis / Q000453:epidemiology / Q000517:prevention & control*; D002417:Cattle; D002418:Cattle Diseases / Q000453:epidemiology / Q000517:prevention & control*; D004196:Disease Outbreaks / Q000517:prevention & control / Q000662:veterinary*; D008297:Male; D016052:Protozoan Vaccines / Q000592:standards*; D011793:Queensland / Q000453:epidemiology; D014613:Vaccines, Attenuated / Q000592:standards
chemical_list: D000913:Antibodies, Protozoan; D016052:Protozoan Vaccines; D014613:Vaccines, Attenuated