INFESTATIONS OF THE BENT TICK AMBLYOMMA-HEBRAEUM (ACARI, IXODIDAE) ONDIFFERENT BREEDS OF CATTLE IN ZIMBABWE

Infestations of adults and nymphs of Amblyomma hebraeum were counted o n Brahman (Br), Brahman x Simmental (BS), Sanga (Sa) and Hereford (He) steers exposed to infested pastures at Mbizi in southern Zimbabwe in 1986-1987. Herefords were always the most heavily infested, while the Sanga tended to carry the fewest ticks with the Brahman and Brahman x Simmental groups being in between. The ratios of the engorged females on the four breeds were 2.3: 1.4: 1.4:1.0 for He:Br:BS:Sa. The ratios of the standard nymphs were 2.2: 1.4:1.7:1.0 for He:Br:BS:Sa. The resu lts confirm earlier observations in Africa and support the view that t here are genetic differences between breeds in the expression of resis tance to this tick species.