In vivo treatment against ichthyophthiriasis in nile tilapia (Oreochromis niloticus l.) using crude methanolic garlic (Allium sativum l.) extract

Abstract

Ichthyophthiriasis is a disease that threatens the freshwater aquaculture industry worldwide. Present medications are known to be harmful to humans and the environment, hence alternative treatments are widely sought-after. This study investigates the potential use of garlic (Allium sativum) as an alternative treatment. One hundred twenty Nile tilapia (Oreochromis niloticus) were experimentally infested with Ichthyophthirius multifiliis and divided randomly into six groups (n=20 per treatment). Different concentrations of crude methanolic garlic bulb extract (62.5 mg/L, 117 mg/L, 570 mg/L) were applied to the experimental groups. A positive control group treated with methylene blue, a solvent control group treated with methanol, and a negative control group with no treatment were likewise employed in this study. At the end of the 96-hour treatment period, the median infestation level of all three garlic treatment groups fell from 2 (10-50 trophonts) to 0 (0 trophont). The methylene blue group similarly decreased to a median infestation level of 1 (1-10 trophonts), while the methanol and negative control groups increased to 2.5 and 3 (50-100 trophonts) respectively. Weight loss was observed in fish across groups. Toxicity of the extract resulted in significantly lower survival at high doses (96-hr LC50=82.59 mg/L). Weight loss was observed across treatment groups. Histopathological findings in extract groups were consistent with chemical irritation. Therefore, although garlic extract is able to reduce ich infestations, further exploration of active components is recommended to maximize anti-ectoparasitic activity and minimize toxicity.