Avaliação da atividade acaricida de monoterpenos e fenilpropanóides sobre Rhipicephalus microplus (Canestrini, 1888), Dermacentor nitens (Neumann, 1897), Amblyomma cajennense (Fabricius, 1787) e Rhipicephalus sanguineus (Latreille, 1806) e observações preliminares sobre o estudo de ectoparasitos em aves silvestres de fragmentos de Mata Atlântica da Zona da Mata de Minas Gerais

Abstract

The present study aimed to evaluate the efficiency of hydroethanolic formulations of carvacrol, (E)-cinnamaldehyde, trans-anetol and linalool against larval stages of Rhipicephalus microplus and Dermacentor nitens. It was also realized assays to evaluate the acaricide effect of carvacrol, thymol, eugenol and (E)-cinnamaldehyde in different concentrations in larvae and nymph of Rhipicephalus sanguineus and Amblyomma cajennense. All substances were tested in concentrations of 2.5, 5.0, 10.0, 15.0 and 20.0 μl/ml, thymol, tested in mg/ml; 10 repetitions were made for each treatment. It was also made with ethanol in a concentration necessary to solubilize each substance. The experimental groups were maintained in BOD incubator (27±1°C e UR>80±10%) during 24 hours and after this period the mortality was available. In the assays with R. microplus and D. nitens larvae, carvacrol and (E)-cinnamaldehyde caused mortality higher than 98% in all the tested concentrations, the trans-anetol caused a mortality of 100% in larvae from a concentration of 5.0 μl/ml; however, linalool was not efficien even at the higher concentration causing a mortality of only 14.5 and 8.4% in R. microplus and D. nitens, respectively. In assays realized with A. cajennense larvae, the concentration of 5.0 μl/ml of carvacrol, thymol and (E)-cinnamaldehyde cased a mortality of 100%; for eugenol this percentage was obtained from the concentration of 15.0 μl/ml. The test realized with R. sanguineus larvae, groups treated with the lower concentration (2.5 μl/ml) of carvacrol and (E)-cinnamaldehyde presented a mortality of 100%; nevertheless, for eugenol this percentage was observed only from the concentration of 10.0 μl/ml. For nymphs of the same species, the monoterpenes carvacrol and thymol from the lower concentration (2.5 μl/ml or mg/ml) caused a lethality of 100% in all concentrations, different from results obtained for eugenol and (E)-cinnamaldehyde, once mortality of 100% with these substances were observed only from the concentration of 10.0 μl/ml. In assays with A. cajennense, the mortality of larvae treated with carvacrol, thymol, eugenol and (E)-cinnamaldehyde in concentrations of 2.5 μl/ml of 45, 62.7, 10.2 and 81.6%, reaching 100% in the concentration of 5.0 μl/ml for carvacrol, thymol and (E)-cinnamaldehyde. For eugenol mortality rate was observed from the concentration of 15.0 μl/ml. For nymphs, tests with carvacrol and thymol caused a mortality of 100% of individuals from concentrations of 5.0 μl/ml and 10.0 mg/ml, respectively; the eugenol only reached this mortality rate at 20.0 μl/ml concentration, while the maximum mortality with (E)-cinnamaldehyde did not exceed 64%. The results indicate that monoterpenes and xiv phenylpropanoids, eugenol and (E)-cinnamaldehyde have deleterious activity in this ectoparasites. Thus, new researches are needed with other developmental stages of these tick species, the investigation of synergism between the substances, aside from tests in natural conditions. As regarding the preliminary observations of the presence of ectoparasites in wild birds, were examined 72 birds from 17 species different with prevalence of 29.2% ectoparasites.