Abstract
BackgroundIndicine 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.FindingsThis 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 cm2 (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 cm2). 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).ConclusionsSpacing 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.
Highlights
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
Spacing between papillae is smaller in Nelores, their tongues may be rougher and, more effective in removing tick larvae during self-grooming, explaining the greater resistance to ticks among Zebu breeds of cattle
The hypothesis of the present study is that morphological features of tongues differ between tick-resistant and tick-susceptible breeds of bovines in such a manner that grooming and tick removal is more efficient in resistant breeds
Summary
Background and hypothesis The importance of self-grooming for reducing tick infestations in cattle is well documented and is one of the most important defense mechanisms against this parasite [1,2,3,4,5,6]. The tongue is the main tool that ruminants and other animals use for grooming [7,8,9,10,11]. Veríssimo et al Parasites & Vectors (2015) 8:594 papillae are located mainly in the anterior third of the tongue and are used for grooming [15]. The hypothesis of the present study is that morphological features of tongues differ between tick-resistant and tick-susceptible breeds of bovines in such a manner that grooming and tick removal is more efficient in resistant breeds. The present study’s aims are to describe and compare the filiform papilla from an indicine breed (Nelore) and two taurine breeds (Holstein and Brown Swiss) of cattle and to correlate the possible differences in tongue morphology observed in each breed with the tick loads they present
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