Seasonal and landscape patterns of Fasciola infection in cryptically diverse Radix natalensis snails in the Lake Albert region, Uganda

Abstract

Fasciolosis is a zoonotic foodborne trematode infection involving freshwater lymnaeid snail intermediate hosts and is highly prevalent among livestock in Uganda’s Lake Albert region. However, xenomonitoring data remain limited, particularly regarding cryptic Radix diversity and ecological predictors of infection. This study investigated Radix molecular diversity and the spatial and seasonal patterns of Fasciola-trematode infection. A longitudinal survey of 18 freshwater habitats in Kagadi District was conducted during the dry (June–July 2020) and wet seasons (October–November 2020). Radix snails were morphologically identified and screened for fasciolid and other trematode infections using multiplex rapid diagnostic PCR (RD-PCR) and genotyped using Cytochrome c Oxidase subunit I (COI) and Internal Transcribed Spacer (ITS) markers. Logistic regression was used to evaluate the association of spatio-temporal factors with infection patterns. Among 220 Radix snails, overall trematode and FasciolaQ3 prevalence were 63.18% (139/220) and 8.64% (19/220), respectively, with sequence analysis confirming Fasciola gigantica (99.41–100% identity-PZ297442). Phylogenetic and haplotype analyses revealed two sympatric Radix natalensis sensu lato subspecies, R. n. debaizei and R. n. exsertus, harbouring infections. Fasciola (p=0.013) and overall trematode (p=0.005) prevalence were significantly higher during the dry-season, while overall trematode prevalence was also higher below the escarpment (p=0.003). Seasonal and spatial variation are strongly associated with Fasciola spp. and other trematode infections in snail populations, with higher prevalence during the dry-season and at sites below the escarpment. Targeted dry season snail control, particularly at infection hotspots, combined with water-trough use, may reduce livestock exposure