Immunization of cattle against Boophilus microplus using extracts derived from adult female ticks: Effects of induced immunity on tick populations

Abstract

Immunization of cattle against Boophilus microplus using extracts derived from adult female ticks: effects of induced immunity on tick populations. International Journal for Parasitology 16: 27–34. Injection of extracts derived from adult female ticks induced partial immunity to B. microplus in both Bos tawus and Bos taurus × Bos indicus breeds. Cattle showed a variable response to vaccination with the complete extract; 7/15 showed good resistance to ticks, 5/15 were intermediate and the remaining three animals showed poor resistance. The immunity induced was still evident after 14 weeks of daily challenge with 1000 larvae and tick populations on vaccinated cattle were reduced by 70% compared to matched controls during this period. In another experiment, cattle were challenged twice with 20,000 larvae and tick populations on the vaccinated group were reduced by over 90% compared to a matched unvaccinated group. Following vaccination, serum antibodies to soluble extracts of adult ticks were detected by gel diffusion and radio-immunoassay but antibody levels in individual cattle were not correlated with their immunity to ticks. Protective antigens were found both in the supernatant and the pellet derived from tick extracts. Insoluble complexes formed by reacting serum from successfully vaccinated cattle with soluble crude tick extracts were not protective.