In vitro ovicidal activity of mixture of linalool and estragole against gastrointestinal nematodes of sheep

Abstract

Based on the results in different studies conducted so far, plant essential oils (EOs) are recently been marked as a possible solution for the problem of anthelmintic resistance (AR). However, their efficacy against a wide range of livestock parasites is due to active ingredients. In that context, the aim of this study was to evaluate the in vitro ovicidal effect of a mixture of linalool and estragole (14% : 86%, respectively) against sheep gastrointestinal nematodes (GINs) using the egg hatch test (EHT). The study was conducted using faecal samples of naturally infected sheep by GINs from two different farms located in Southern Italy. Coproculture of tested faecal samples was performed, as well as chemical analyses of the tested mixture. The egg hatch test (EHT) was performed at six different concentrations (50, 12.5, 3.125, 0.781, 0.195 and 0.049 mg/mL) and the obtained values were compared to the positive control (thiabendazole, 0.025 mg/mL) and the negative control (3% Tween 80, v/v). The tested binary combination showed high and dose-dependent ovicidal activity varied from 29.5% to 100%. The inhibitory effect on egg hatchability was similar (p>0.05) to the positive control (98.0%) at concentrations of 50 mg/mL (100%), 12.5 mg/mL (100%) and 3.125 (99.8%). Moreover, all tested concentrations showed significantly higher (p<0.001) activity compared to the negative control. The obtained results suggest that the combination of linalool:estragole has the potential to be used against sheep GINs. These also highlight the possible role of different combinations of certain constituents of essential oils in combating AR. However, these findings need confirmation in further in vivo studies.