Efeito dos isômeros α-pineno e β-pineno no desempenho reprodutivo de fêmeas ingurgitadas de rhipicephalus microplus (Acari: Ixodidae)

Abstract

Rhipicephalus microplus are important ticks in veterinary medicine and public health because they are vectors of several pathogens, especially for cattle. Due to the selection of resistant strains to synthetic chemicals used to control these ticks and their toxicity to hosts, there is a need to identify new substances that are effective and cause fewer adverse effects. Pinenes are known for their various biological effects, such as their insecticidal action, for example. For this reason, in the present study, the effects of α and β-pinene commercially obtained on the reproductive performance of the cattle tick were evaluated. For this, the products were diluted in different concentrations in a 2% Tween 80 aqueous solution. Female R. microplus ticks were previously weighed and subsequently immersed in the test solutions for five minutes. Then, the animals were dried with paper towels and fixed dorsoventrally in Petri dishes, totaling five treatment groups for each pinene and a control group. Ticks were monitored daily, and their eggs were collected, weighed and maintained at 27°C in a BOD incubator. The larval hatching rate was visually estimated, and the pre-oviposition and egg incubation periods were determined. From these data, the egg production index, the fecundity rate, the estimated reproduction rate, the percentages of oviposition and hatching reduction and the effectiveness of the product were determined. α-pinene showed dose-dependent results, unlike β-pinene, which was more effective at lower concentrations. The efficacy of α-pinene was 74% at 14.0 μL/mL, while β-pinene showed efficacy of 78% at 2.0 μL/mL. The results showed differences in the effects of both pinenes suggesting that both compounds, in addition to presenting acaricidal potential, affected the reproduction of engorged females of R. microplus.