The Bovine Major Histocompatibility Complex and Its Role in Tick and Tick-borne Disease Resistance and Immune Responsiveness in Bos Indicus and their Crosses with Bos Taurus in Sub-Saharan Africa: A Review
Ticks present a major challenge in livestock production given the increased demand for animal protein worldwide. Ticks cause worry, blood loss, damage hides and most importantly they are vectors of pathogens that cause severe diseases in livestock. Economic losses caused by ticks amounts to billions of dollars annually. The primary tick control method relies heavily on the use of acaricides. The increasing prices of these chemicals, environmental pollution, chemical residues in animal products and most importantly evolution of resistance of ticks to almost all available acaricides, has frustrated efforts of farmers to control ticks and tick-borne diseases. This has motivated researchers to search for alternative methods of tick control. The Major Histocompatibility complex (MHC) which is called Bovine Leuckocyte Antigen (BoLA) in cattle is an important component of the immune system which plays a major role in immune responses. The BoLA-DRB3 gene is the most polymorphic MHC class II gene locus where numerous associations have been found between the MHC polymorphism and disease resistance making it a good gene candidate for tick resistance. The Bos indicus breed is known to be more resistant to ticks and tick-borne diseases than the Bos Taurus. The use of tick and tick-borne disease resistant cattle breeds is a promising choice for tick and tick-borne disease control given the downsides of acaricides, vaccines and other tick control methods. This review summarizes available information on ticks and tick-borne diseases and the role of the Major Histocompatibility Complex in tick and tick-borne disease resistance.