Anthelmintic activity of garlic (Allium sativum) against the monogenean Dawestrema cycloancistrium and trichodinids, and its physiological effects on pirarucu (Arapaima gigas).

The use of phytotherapeutics in aquaculture has been widely studied as an alternative for controlling ectoparasites in fish. Therefore, the objective of this study is to investigate the anthelmintic activity of Allium sativum against the monogeneans Dawestrema cycloancistrium and trichodinids, as well as to evaluate the physiological effects of the treatment on the hematological, biochemical, and parasitological parameters of Arapaima gigas. Naturally parasitized juveniles of A. gigas were subjected to therapeutic baths for 96 h at different concentrations of A. sativum (0, 2.5, 5.0, 7.5, and 10 mg/L). The intensity of D. cycloancistrium in the gills was significantly reduced (p < 0.05) in treated fish compared to the control, but no differences were observed between the tested concentrations. The efficacy of the baths against monogeneans was below 40 % for all treatments. For trichodinids, a significant increase in the number of dead parasites was observed in fish exposed to garlic (p < 0.05), with the highest efficacy at a concentration of 5.0 mg/L. No significant changes were detected in hematological parameters, but glucose (p < 0.02) and AST (p < 0.001) levels decreased at the highest tested concentrations (7.5 and 10 mg/L). No mortality or behavioral alterations were observed during the experiment. The results suggest that A. sativum may be a promising phytotherapeutic alternative for managing ectoparasites in fish farming, particularly at a concentration of 5.0 mg/L for 96 h of exposure.