Determination of the LC50 of selamectin (active principle of the antiparasitic Revolution (R), Pfizer) applied on engorged female of the tick Rhipicephalus sanguineus (Latreille, 1806) (Acari: Ixodidae)

Abstract

Ticks have great medical and veterinary importance because they transmit several pathogens to their hosts, including humans; moreover, they cause skin lesions and favour secondary infections and blood loss. Selamectin, a macrocyclic lactone, has been used as a potent antiparasitic and is commercialized in Brazil as a product called Revolution (R) manufactured by Pfizer Animal Health (Guarulhos, São Paulo, Brazil). There is little information on the method of action of this chemical compound on tick physiology so this study presents an analysis of the toxic potential of selamectin on engorged females of the tick Rhipicephalus sanguineus. For the toxicity study of selamectin, the adult immersion test was performed, in which individual ticks were exposed to different concentrations of the chemical compound. The percentage of dead females was submitted to probit analysis to determine the median lethal concentration (LC50) of selamectin. Bioassays showed that R. sanguineus females are sensitive to the chemical compound and the LC50 was 451.221 ppm. This study proposes a protocol for determining the LC50, which will contribute to future research related to the toxicity of other chemical products that are used for tick control, as well the chemical compounds' effect on these parasites, showing that lower concentrations than those originally traded is sufficient to kill these ectoparasites, providing a better conservation to the environment and to non-target organisms.