Tick-borne fever: a review.

The literature on tick-borne fever is reviewed. Tick-borne fever is a rickettsial disease of sheep and cattle characterised by high fever and severe leucopaenia. The causative agent, Cytoecetes phagocytophila invades the neutrophils and monocytes and is transmitted by the tick Ixodes ricinus. There is very little information on the pathogenesis and immunogenesis of the disease but there is ample evidence that infected animals are predisposed to other diseases. Animals infected with tick-borne fever resist reinfection for a variable period of time. The organisms may persist in the blood of recovered animals for up to two years. Humoral antibodies are produced two weeks after infection and continue to be detected for many months but their significance on protective immunity is not clearly established.