Fluazuron no controle do carrapato Amblyomma sculptum: eficácia, farmacocinética e palatabilidade utilizando o porquinho-da-índia como modelo experimental

Abstract

The tick Amblyomma sculptum is known for the fact that its bite causes extremely itchy lesions and for being the transmitting species of the bacterium Rickettsia rickettsii, which causes Brazilian Spotted Fever in humans. Any of its parasitic stages can be found in domestic and wild animals and even in humans, but the capybara is one of its preferred hosts. Due to the similarity between capybaras and guinea pigs, this second species was used to carry out this work, replacing the first one. The general objective of this work was to evaluate the efficacy of fluazuron in the control of the tick A. sculptum in guinea pigs artificially infested with larvae. The work was divided into six stages that occurred chronologically (Study I to VI). In Study I, the influence of three different doses of fluazuron administered by gavage on plasma concentration and efficacy in controlling A. sculptum in guinea pigs was determined. In Study II, the descriptive pharmacokinetics of fluazuron was performed after its administration by gavage to guinea pigs. With the results obtained in the first two studies, in Study III, different bait formulations were developed that underwent evaluations of organoleptic characteristics and resistance to different temperatures and humidity. Fluazuron was incorporated into the chosen formulation, which underwent dose uniformity tests. Subsequently, Study IV was conducted to assess the palatability of the formulation developed for guinea pigs, where baits containing fluazuron (treated group) and placebo group (not treated) were offered. In Study V the baits were administered to guinea pigs to complete the descriptive pharmacokinetics of fluazuron, following the same methodology applied in Study II. In this step, the animals were divided into groups where each received the bait containing fluazuron in a single dose on different pre-infestation experimental days. In Study I, the efficacy results showed that even the lowest dose achieved 100% efficacy against molting engorged larvae. As for plasma bioavailability, there was an increase in the plasma concentration of fluazuron with the increase in dose on day +1. However, from day +4 to the last day of evaluation (+21), mean plasma concentrations did not differ significantly between groups. In Studies II and V, fluazuron plasma concentrations increased rapidly, indicating rapid absorption and slow elimination. The results allowed the development of a bait resistant to different temperatures and humidity, which fluazuron was incorporated and approved in the dose uniformity tests (Study III). In Study IV the placebo and treated baits were palatable to guinea pigs at least 92% of the time. In Study VI, the efficacy obtained was 64.99% for the treated animals 21 days before the infestation, 61.88% for the animals treated 14 days before the infestation and 59.31% for the animals treated 7 days before the infestation. Fluazuron was effective in controlling the A. sculptum tick in guinea pigs.