In-vitro Larvicidal Potentials of Achillea Extracts on Strongylid Larvae

Strongylid infections remain among the most widespread and clinically significant helminthoses in horses, with increasing concerns regarding anthelmintic resistance. Against this background, we investigated the in-vitro larvicidal activity of Achillea salicifolia and Achillea setacea extracts against strongylid larvae. We evaluated concentrations of 20, 30, and 40% at exposure times of 0.5, 1, 2, and 4 h (n = 3). Larval motility was assessed microscopically and expressed as mean ± standard deviation (M ± SD). A pronounced dose- and time-dependent reduction in larval motility was observed. For A. salicifolia at 40%, motility was 23.0 ± 3.2% after 30 min, 7.0 ± 1.8% after 1 h, and 0% after 2 h (p < 0.001 vs control). At 30%, motility decreased to 41.0 ± 4.5%, 19.0 ± 3.7%, 4.0 ± 1.5%, and 0% at 0.5, 1, 2, and 4 h, respectively (p < 0.01). At 20%, motility values were 58.0 ± 5.1%, 33.0 ± 4.2%, 12.0 ± 2.8%, and 0% at 4 h (p < 0.05). For A. setacea at 40%, motility was 49.0 ± 5.4% after 30 min, 13.0 ± 2.6% after 1 h, and 0% after 2 h (p < 0.01). At 30%, values were 61.0 ± 6.2%, 37.0 ± 4.9%, 11.0 ± 3.1%, and 0% at 4 h (p < 0.05), whereas at 20%, motility remained at 72.0 ± 6.8%, 54.0 ± 5.7%, 25.0 ± 4.3%, and 4.0 ± 1.2% after 4 h (p < 0.05). The positive control (4% phenol) induced 100% larval immobilization within 1 h (p < 0.001), whereas in the negative control, motility remained at 100% throughout the observation period. The results indicate a strong larvicidal effect of the studied extracts, with a more rapid and pronounced activity observed for A. salicifolia, supporting the potential of Achillea species as a source of natural anthelmintic agents.