Abstract

VILLAR, David et al. In vitro resistance to topical acaricides of the cattle tick Rhipicephalus (Boophilus) microplus from four regions of Colombia. Ces. Med. Vet. Zootec. [online]. 2016, vol.11, n.3, pp.58-70. ISSN 1900-9607.

In Colombia, the control of the cattle tick Rhipicephalus (Boophilus) microplus lies almost exclusively on the use of chemical acaricides. However, R. (B.) microplus has developed resistance to most of the commercially available products. The aim of this study was to assess the degree of resistance to the major topical acaricides used in Colombia. The adult immersion test was used as recommended by FAO with ticks from 7 farms originating in 4 distant Colombian regions. The efficacy of the products was calculated based on the reproductive parameters of fecundity and fertility with groups of ticks (n = 40) exposed to the recommended concentrations of each acaricide, and compared with the respective control group exposed to distilled water. In general, products containing deltamethrin (25 ppm) and amitraz (208 ppm) were less effective, with efficacy values of <20% and 10-50%, respectively. Doubling the concentration did not increase the efficacy of either compound. The combination of chlorpyrifos (312 ppm) + cypermethrin (150 ppm) showed great variation between farms, with an efficacy ranging between 22-93%. Unlike chlorpyrifos, the organophosphorus ethion (622 ppm) was 99-100% effective in completely inhibiting oviposition in 4 of the 7 farms. In conclusion, resistance to deltamethrin and amitraz is very high in seven distant strains of the Colombian territory, varies widely for chlorpyrifos, and was not detected for ethion that was 99-100% effective

Keywords : cattle; acaricides; resistance; ticks.

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