Difficulties to control natural infestation with Otobius megnini (Acari: Argasidae) nymphs in cattle with systemic biocides.

A study was carried out to determine the efficacy of topical eprinomectin against nymphal infestation of Otobius megnini in cattle, where a group of 14 individuals were treated with a dose of 0.5mg/per kg of body weight applied on the dorsal midline, and a group of 14 individuals remained as control. Tick burdens between treated and control groups showed no statistically significant differences (P>0.05), and the mortality of the nymphs was similar in both groups (P: 0.828). All females obtained from nymphs of both groups were able to copulate with males from the corresponding group and laid eggs that produced visually normal larvae. The failure of eprinomectin and other biocides applied per os or by injection to control nymphs of O. megnini in cattle indicate that sanitary measures and applications of biocides into the ears would represent the most reasonable approach to control of this tick on cattle.