Acquired resistance in rabbits to immature stages of Rhipicephalus evertsi evertsi.

Host resistance, accompanied by demonstrable anti-tick antibodies, developed in groups of rabbits that were infested repeatedly with different numbers of Rhipicephalus evertsi evertsi larvae. This resistance was associated with a drastic reduction in the number of ticks that attached but not in the ability to feed and moult by immatures already established on the hosts. Furthermore, resistance reduced to below 50% the proportion of nymphs which emerged from the larvae applied to the three host groups. Nymphs weighing 5-9.9 and 15-19.9 mg moulted to give mainly males or females respectively. The proportion of males and females which moulted from the remaining weight categories was variable. Anti-tick antibodies were detected by enzyme-linked immunosorbent assay as early as 7 days after primary infestation in all hosts. The titres plateaued after the second challenge and declined drastically during the fifth infestation. No appreciable differences were observed in the antibody responses stimulated by different challenge regimens.