Resistance of Brahman and Simmentaler cattle to southern African ticks.
Field collections of ticks from 2 breeds of cattle in the north-western Transvaal, South Africa, showed the common tick species to be Rhipicephalus appendiculatus, Amblyomma hebraeum, R. evertsi evertsi and Hyalomma marginatum rufipes. The number of these ticks was higher in Simmental than on Brahman (zebu) cattle. Correlation was found between the number of ticks on the cattle and their serum gamma globulin levels, indicating an increase in the production of antibodies. Similar correlation was found between the number of ticks on the cattle and the number of eosinophils in their blood. Resistance was probably acquired by the hosts and, it appears, to a higher degree in Brahman than in Simmental cattle.