Resistance of Nguni, Bonsmara and Hereford cattle to ticks in a Bushveld region of South Africa.

Counts of engorged female ticks on naturally infested cattle over a 2 year period, showed that indigenous Nguni cattle harboured significantly fewer Amblyomma hebraeum, Boophilus decoloratus and Hyalomma spp. during periods of peak abundance than either Bonsmara or Hereford cattle. Fewer abscesses, associated with tick bite, were also present in the Nguni cattle. Individual tick resistance indices, determined after artificial tick infestation in the field, could not be correlated with hair length, skin thickness or conglutinin titres. The consistently large percentage of Nguni cattle showing high tick resistance according to index determinations, indicates a superior level of natural immunity in this breed. The relative incidence of individuals in high, medium and low resistance classes reflected an increase in resistance with exposure to ticks and the potential for the selection for tick resistance within all 3 breeds.