Molluscicidal Activity of Vernonia amygdalina and Azadirachta indica Leaf Extracts against Bulinus globosus

Abstract

 Bulinus globosus is a freshwater snail that serves as an intermediate host for Schistosoma species, the causative agents of the neglected tropical disease schistosomiasis. Trematode parasites of the genus Schistosoma rely on such snail hosts for transmission, making snail control a critical component of disease management. Consequently, one of the most important aspects of integrated schistosomiasis control strategies is the reduction of snail populations. This study evaluated the molluscicidal activity of methanolic leaf extracts of Vernonia amygdalina (bitter leaf) and Azadirachta indica (neem), applied individually and in combination, against adult Bulinus globosus. Qualitative phytochemical screening was conducted using standard procedures. Molluscicidal bioassays were performed at concentrations ranging from 0 to 128 mg/L, using ten snails per concentration in triplicate, and mortality was recorded at 1, 4, 6, 12, 24, and 48 h. Both plant extracts exhibited concentration- and time-dependent molluscicidal effects, with no mortality observed in control groups. At 48 h, the LC50 values were 56.76 mg/L for V. amygdalina, 51.09 mg/L for A. indica, and 51.03 mg/L for the combined extract, while LC90 values ranged from 108.39 to 123.23 mg/L. Statistical analysis revealed significant differences (p < 0.05) in snail mortality across concentrations and exposure periods. The findings indicate that V. amygdalina and A. indica possess promising molluscicidal properties and may serve as potential plant-based alternatives to synthetic molluscicides in schistosomiasis control programmes. However, the study was limited to adult Bulinus globosus, did not assess effects on non-target aquatic organisms, and utilized crude extracts without characterization of active compounds, which may affect environmental safety assessment and reproducibility.