Resistance in cattle against Rhipicephalus appendiculatus with an assessment of cross-resistance to R. pulchellus (Acari: Ixodidae).

A comparison of the yield of engorged nymphs of Rhipicephalus appendiculatus and R. pulchellus was carried out between cattle highly resistant to R. appendiculatus but susceptible to R. pulchellus, and cattle and rabbits susceptible to both species. Resistant cattle yielded fewer and smaller R. appendiculatus nymphs than either susceptible cattle or rabbits. More nymphs of both tick species dropped from susceptible cattle but no differences were detected in the mean weight of engorged R. pulchellus nymphs fed on R. appendiculatus-resistant and susceptible cattle, although resistant animals yielded more nymphs of R. pulchellus than of R. appendiculatus. An acute inflammatory reaction, accompanied by intense pruritus and grooming, was observed in the ears of the resistant cattle infested with R. appendiculatus, but no reaction was detected in the opposite ears where R. pulchellus was feeding. The low cross-resistance between these two closely related tick species suggests that different antigens may be involved in the development of resistance in cattle to different tick species.