Search

Given the difficulties of controlling the tick Rhipicephalus microplus due to acaricide resistance, this study aimed to ascertain whether shearing could reduce infestation in cattle. 17 taurine cattle were sheared on the anterior third of one randomly selected side. Shearing was undertaken using a machine with a blade, leaving coats with a thickness of 1 mm. Subsequently, eight evaluations were performed once a week, counting adult females of R. microplus with a diameter > 4.5 mm on the anterior third of both sides (shorn and unshorn). The coat length was also monitored by taking five hair samples from each animal fortnightly (1, 15, 29, 43 and 57 days post shorn) from a central area of both shoulders (shorn and unshorn). The tick counts and hair length data were transformed for normalisation and were analysed using mixed models. The tick and hair length means were significantly higher for the unshorn side. Tick counts were significantly lower on the sheared side until the fifth evaluation, with the final three presenting no differences between the sides. The hair length was significantly lower for the sheared side during the five evaluations. We conclude that as the hair length increased, there was also an increase in the number of ticks on the sheared side. Although this method is not practical for large herds, it can be deemed an option in extreme conditions of tick infestation. In addition, the study reinforces the suggestion that the selection and/or use of cattle with shorter hairs may contribute to reduced tick infestation.

Background: Indicine breeds of bovines are highly resistant and taurine breeds are susceptible to the cattle tick, Rhipicephalus microplus, a species which causes great damage to livestock. Animals use their tongues for self-grooming, an important behavior for ridding themselves of ectoparasites. However, the role of tongue morphology, notably the filiform papillae, in this process is not known., Findings: This study compared features of the filiform papillae of tongues in eight Nelores (indicine breed) and eight Holsteins and two Brown Swiss (taurine breeds) and verified how they associate with tick loads. Biopsies were taken from identical positions of tongues and measured by scanning electron microscopy. One-way analysis of variance detected significant differences between morphological features of tongues from indicine and taurine breeds: Nelores had longer papillae (mean of 2.3 mm ± 0.029 SD; P < 0.001), and more papillae per cm(2) (mean of 25.2 papillae ± 1.92 SD; P < 0.05) than European bovines (means of, respectively, 1.8 mm ± 0.027 SD and 20.9 ± 0.74 SD papillae per cm(2)). After infestations with equal numbers of larvae, loads of adult ticks were inversely correlated with length of papillae and directly correlated with distances between the apices of papillae (P = 0.014; r = -0.566 and P = 0.018; r = 0.567, Pearson product momentum correlation, respectively)., Conclusions: Spacing between papillae is smaller in Nelores, thus their tongues may be rougher and, consequently, more effective in removing tick larvae during self-grooming, explaining the greater resistance to ticks among Zebu breeds of cattle.