The effects of nutritional status of rabbits and sheep on their resistance to the ticks Rhipicephalus evertsi evertsi and R. appendiculatus.

Rabbits and sheep were exposed to low- and high-protein diets and subsequently infested three times with adults of Rhipicephalus appendiculatus and Rhipicephalus evertsi evertsi. The mean weight of R.e. evertsi females which dropped from rabbits maintained on a high-protein diet decreased from 515.0 +/- 24.9 mg (naive) to 381.5 +/- 25.0 (second infestation) to 340.3 +/- 23.3 mg (third infestation) while the weight of ticks fed on animals which were exposed to a low-protein diet did not change significantly (2.7%). The mean weight of engorged females of R. appendiculatus which completed their blood meal on rabbits (high protein) decreased from 520.9 +/- 31.8 (naive) to 369.3 +/- 39 mg (3rd infestation), a significant decrease of 29.1% compared to a 12.3% decrease in weight between the 1st and 3rd infestation of females fed on animals on a low-protein diet. Rhipicephalus e. evertsi fed on sheep exhibited the same phenomenon. The mean decrease in weight of 4rd-infestation ticks which dropped from sheep fed lucerne was 26.2% compared to 16.6% for ticks from sheep which were fed on grass. Hosts maintained on a low-protein diet failed to acquire resistance to ticks, lost weight and developed anaemia while those on a high-protein diet developed resistance, maintained weight and did not develop anaemia. The nutritional stress of the hosts and its application in South Africa are discussed.