Questing for sustainable control of cattle ticks: bottlenecks in developing efficacious vaccines.

Naturally acquired immunity against cattle ticks, observed in certain breeds of cattle, indicates that development of vaccines to prevent infestations is feasible. This opinion article focuses on the knowledge needed to guide their development, formulation, and testing. It discusses the limitations of current experimental vaccines and tests used to evaluate them and points to the research needed to achieve a truly efficacious vaccine. It includes using better strategies to select antigens, not relying solely on indirect readouts of efficacy but rather elucidating the immune mechanisms responsible for reducing tick loads and overcoming the low coverage of the host's major histocompatibility complex class II molecules, as well as avoiding confounding factors in designs for testing vaccines and considering management practices that impact efficacy.