Small-Scale Field Trials to Assess the Molluscicidal Activity of Hagenia abyssinica Against Biomphalaria Snail Species.

Schistosomiasis remains a significant public health burden in many developing countries. Plant-based molluscicides have gained considerable attention as alternatives for snail control, owing to their relatively lower toxicity and favorable environmental profile. However, prior to large-scale application, plant-based molluscicides require rigorous small-scale field trials and comprehensive toxicity assessments under natural conditions to confirm their efficacy and evaluate their potential impact on nontarget organisms, particularly fish. This study evaluated the molluscicidal activity of 70% ethanol and chloroform fractions of Hagenia abyssinica flowers against Biomphalaria species and assessed the acute toxicity of the 70% ethanol extract on Nile tilapia (Oreochromis niloticus) through a small-scale trial. Female flowers of H. abyssinica were collected in Addis Ababa, Ethiopia. Adult Biomphalaria species were exposed to 70% ethanol and chloroform fractions of H. abyssinica for 24, 48, and 72 h. Fish toxicity was assessed following the Organisation for Economic Co-operation and Development guidelines at the National Fish and Other Aquatic Lives Research Center in Sebeta. Lethal concentration values (LC50 and LC90) were calculated from mortality data using probit regression analysis in IBM SPSS software. In fish toxicity assessments, the LC50 and LC90 for the 70% ethanol extract were 38.71 and 57.14 mg/L, respectively. Fish fingerlings showed no significant difference in survival at concentrations up to 16 mg/L, establishing this level as the no observed adverse effect concentration (NOAEC). The study found that both the 70% ethanol extract and chloroform fraction of H. abyssinica flowers displayed significant molluscicidal activity against Biomphalaria species, with LC50 values of 78.77 and 36.49 mg/L, respectively, after 24 h. The LC50 of the 70% ethanol extract for molluscicidal activity was about twice that needed for fish, showing that fish were more sensitive than Biomphalaria snails. This differential toxicity raises important ecological concerns.