Abundance and Distribution of Snail Intermediate Hosts of <i>Fasciola</i> spp. a High-Risk Fascioliasis Ecosystem in Western Kenya

Trematode infections are still one of Africa’s most common and pervasive tropical diseases, especially in areas near freshwater bodies<i>. Fasciola </i><i>gigantica</i> transmission in East African wetlands is shaped by the ecology of its freshwater snail hosts, yet fine-scale dynamics remain poorly resolved. This study quantified spatial, temporal, and spatio-temporal patterns of snail populations in Kingwal Wetland, in western Kenya, through monthly surveys of the snail host from January–December 2023 at seven ecologically distinct sites. A total of 8,754 snails belonging to eight different species were collected; dominant taxa were <i>Biomphalaria sudanica</i> (21.0%), <i>B. pfeifferi</i> (17.9%), <i>Lymnaea auricularia</i> (13.6%), <i>Bulinus globosus</i> (12.8%), and <i>Radix natalensis</i> (6.0%). The confirmed <i>F. gigantica</i> vectors, <i>L. auricularia</i> and <i>R. natalensis</i>, the snails showed distinct spatial patterns, with <i>R. natalensis</i> reaching a peak infection prevalence of 29.3% in June. Species abundance differed significantly across the sites (χ² = 3,284.77, df = 42, p < 0.001): Sites 1–3 exhibited the highest snail species diversity and abundance, whereas Site 7 exhibited consistently the lowest, likely reflecting anthropogenic disturbance and seasonal desiccation. Snail populations peaked during the long rains (May–August), with the highest monthly count in May (n = 1,383), and were lowest in January (n = 230) and December (n = 316), confirming strong seasonal effects (χ² = 839.27, df = 77, p < 0.001) and a significant spatio-temporal variation (CMH = 1,192.37, df = 11, p < 0.001). These findings indicate that fasciolosis transmission potential is greatest in wet months within stable, vegetation-rich habitats. The identification of a seasonal transmission window highlights a key timeframe for implementing targeted snail control measures, habitat management, and enhanced surveillance to disrupt <i>F. gigantica</i> transmission in wetlands.