Ability of adults of Amblyomma hebraeum (Acarina: Ixodidae) to feed repeatedly on sheep and cattle.

Adult Amblyomma hebraeum ticks were exposed at 14-day intervals on five sheep on 46 occasions and on three cattle on 15 occasions to determine the effects of repeated feeding. The engorged weight and percentage of ticks which fed successfully on sheep declined significantly at first but subsequently they increased. On cattle there was no progressive decline in engorged weight, although the percentage which fed successfully declined significantly and was lower than that for sheep. This decline was attributed to increased grooming by cattle and was the only apparent mechanism by which resistance was expressed.