Abstract
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.