First documentation of dose response of Amblyomma cf. parvum population infesting dogs to amitraz, coumaphos, and cypermethrin.

Amblyomma cf. parvum (Ixodida: Ixodidae) is an ectoparasite of domestic animals and wildlife on the American continent. There is little information on the efficacy of acaricides for the control of this tick species in domestic animals. Here, we determined the toxicological response of A. cf. parvum to amitraz, coumaphos, and cypermethrin. Engorged females of A. cf. parvum were collected (in two periods, eight months apart) from dogs in Yucatan, Mexico. The larval immersion test was used on the progeny of adult female ticks to test for amitraz susceptibility, and the larval package test was used to test for coumaphos and cypermethrin susceptibility. Dose-mortality regressions, lethal concentrations (LC), 95 % confidence intervals (CI95 %), and slopes were estimated by probit analysis. The lethal concentrations to kill 50 % of the tick population for amitraz, coumaphos, and cypermethrin in the first period were 1 ppm (CI95 %: 1-3 ppm), 10 ppm (CI95 %: 9-11 ppm), and 10 ppm (CI95 %: 9-10 ppm), respectively; meanwhile in the second period were 2 ppm (CI95 %: 1-3 ppm), 8 ppm (CI95 %: 6-10 ppm), and 9 ppm (CI95 %: 8-10 ppm), respectively. In conclusion, amitraz, coumaphos, and cypermethrin demonstrated high larvicidal efficacy in in vitro bioassays against A. cf. parvum populations infesting dogs.