Influence of water quality parameters on lymnaeid snail distribution and their relationship with fasciolosis transmission.

Fascioliasis is a globally distributed parasitic disease caused by Fasciola hepatica and Fasciola gigantica, transmitted by freshwater snails of the family Lymnaeidae. Although environmental factors influence the distribution of these intermediate hosts, the role of water physicochemical parameters remains underexplored. This study evaluated the relationship between water quality and lymnaeid snail presence in endemic areas of western Argentina. A total of 53 aquatic sites were surveyed, with lymnaeid snails detected in 33 (62.26 %). Water samples were categorized as positive or negative based on snail presence and F. hepatica detection in livestock from the associated farm. Significant differences were observed in electrical conductivity, total dissolved solids, pH, total hardness, calcium, sodium, and sulfate concentrations. Correlation analysis revealed a consistent negative association between lymnaeid presence and most parameters, particularly calcium and total hardness. Notably, snails were found in sites with water temperatures as low as 2.8°C, challenging previous assumptions about thermal limits for survival. Consistently with these environmental findings, coprological analysis of 1936 animals showed a strong association between snail presence and F. hepatica infection: all farms in snail-positive areas tested positive (19/19), while none in snail-negative areas did (0/10) (Fisher's exact test, p < 0.001). Overall prevalence in snail-positive farms was 36.48 %, with species-specific rates ranging from 25.51 % in cattle to 50.91 % in goats. These findings provide actionable insights for environmental surveillance and fascioliasis control strategies in endemic regions, especially under changing climatic conditions.