Avaliação da Repelência e Atividade Acaricida de Formulações Contendo Alecrim-do-Campo, Hortelã e Eucalipto Contra o Carrapato Amblyomma sculptum

Abstract

Ticks are parasites of medical and veterinary importance, especially due to the blood plunder they exert on their hosts and because they are vectors of pathogens. Problems with ticks have become more frequent in urban and peri-urban areas of the Southeast region, reflecting an increase in the number of individuals bitten by these arthropods. Amblyomma sculptum is one of the most important ticks in Brazil, as it is the main species associated with humans, it is the main vector of the bacterium Rickettsia rickettsii, which causes Brazilian Spotted Fever, and causes considerable damage to animal husbandry. The use of repellents and acaricides is one of the main alternatives to prevent problems associated with ticks. However, despite the notable benefits of the available products, they also present problems mainly related to the possibility of developing allergic reactions or intoxication on the part of the host, contamination of the environment and products of animal origin, and the development of resistance on the part of ticks. . Therefore, it is necessary to develop new, more efficient compounds to combat ticks. Products based on plant extracts and essential oils have aroused increasing interest, as several studies have demonstrated their repellent and acaricidal potential against ticks, in addition to being low in production cost, easily accessible and low in toxicity for mammals. This work aimed to test different formulations of hydroalcoholic infusions of wild rosemary (Baccharis dracunculifolia DC) and mint (Mentha spicata), and eucalyptus essential oil (Eucalyptus globulus) in repellency and acaricide tests against A. sculptum. In the repellency tests, infusions of wild rosemary and mint were evaluated at concentrations of 100, 50, 25, 12.5%, and solutions of eucalyptus essential oil (BioEssência®) at concentrations of 0.5, 0 .25, .125 and .0625%, over the period from 10 minutes to five hours. For screening, the formulations were tested using the filter paper climbing test. The solutions with the best average repellency results, during the 5h evaluation, were used to prepare new formulations with binary or multiple combinations that were tested again using the same methodology. Then, the formulations with the highest average repellency over time were subjected to the fingertip climbing test and the larvae immersion test. The individual formulations that presented the best average repellency results over the entire period in the filter paper test were eucalyptus oil 0.5% (78.9% repellency) and 0.25% (75.3%), hydroalcoholic mint infusion 12.5% (69.8%) and hydroalcoholic rosemary infusion 12.5% (69.8%). Among the binary combinations, in the filter paper test, the results showed an average repellency of 86.4% for the formulation rosemary-do-field 12.5% + eucalyptus 0.5%, followed by rosemary-do-field 12.5 % + mint 12.5% (73%) and eucalyptus 0.5% + mint 12.5% (64%). While multiple combinations showed approximately 80% repellency. In the fingertip climbing test, the repellency effects were lower than those in the filter paper test and were between 16.9 and 31.1% repellency, with the formulation 12.5% rosemary + eucalyptus 0.5% most effective. Mortality caused by the four selected solutions ranged from 63.5 to 77%, with rosemary 12.5% + eucalyptus 0.5% and eucalyptus 0.5% being the most active in A. sculptum larvae. The results showed that the three plants have a repellent and acaricidal effect with potential to be explored to combat A. sculptum. However, more studies must be conducted in order to find formulations with better efficacy, evaluate the stability of the formulations, among other parameters that enable their use.