Seasonality, mixed invasions, and risk factors of trematode endoparasites in small ruminants

This observational field and laboratory study evaluated the occurrence, seasonal dynamics, regional distribution, and mono- and mixed-invasion patterns of trematode endoparasites in small ruminants in Central Uzbekistan, together with infection dynamics of Lymnaea truncatula as a key intermediate host. During 2024–2025, 479 fecal samples from sheep and goats from the Bukhara, Navoi, and Samarkand regions were examined, and 5,549 freshwater molluscs were collected from natural aquatic biotopes in the same regions. The trematode taxa investigated were Fasciola hepatica, F. gigantica, Calicophoron calicophorum, Gastrothylax crumenifer, and Liorchis scotiae. Among the 479 animals, 225 cases were classified as mono-invasion (47.0%) and 254 as mixed invasion (53.0%), indicating that mixed invasions were slightly more frequent. Fasciola hepatica was the predominant mono-invasion species. The infection rates of L. truncatula with fasciolid parthenitae and cercariae peaked in August–September in all regions, with the highest values recorded in Samarkand. Regional effects were most clearly demonstrated for F. hepatica mono-invasion: Navoi and Samarkand had significantly higher odds than Bukhara in crude logistic regression. Feeding type, age category, and body condition were recorded as exploratory epidemiological variables but were not confirmed as independent risk factors. These data provide region-specific evidence for seasonally adjusted surveillance and targeted control of trematode infections in small ruminants in Central Uzbekistan.

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