Fasciola Metacercaria Contamination in Wetland Pastures and Its Association With Forage Characteristics Across Agro-Ecological Zones: Case of Gamo Zone, Southern Ethiopia.

Fasciolosis remains a major constraint to ruminant production in Ethiopia, particularly in wetland-based grazing systems where infective Fasciola metacercariae encyst on pasture vegetation. This study investigated metacercarial contamination of wetland herbage and its association with forage characteristics across lowland, midland and highland agro-ecologies of the Gamo Zone, southern Ethiopia. A cross-sectional study was conducted from November 2021 to October 2022, during which 432 herbage samples were collected for parasitological and botanical analysis, and 171 livestock owners were interviewed regarding grazing practices. Metacercariae were recovered using a modified mechanical elution technique and expressed as cysts per kilogram of fresh herbage. Metacercarial burden varied significantly among herbaceous species and agro-ecological zones (p < 0.05), with the highest contamination recorded in lowland (>750 cysts/kg) and highland (>600 cysts/kg) wetlands. Highly palatable and nutritionally superior species, including Trifolium burchellianum, Cynodon nlemfuensis and Scirpus maritimus, harboured the greatest metacercarial loads, demonstrating a positive association between forage quality and contamination risk. Most respondents (97.1%) relied on natural wetlands for grazing, and grazing management practices differed significantly among agro-ecologies (p < 0.05). The findings indicate that wetland pastures in the Gamo Zone are important transmission foci for fasciolosis and that the concurrence of high nutritional value and elevated parasite contamination presents a critical challenge for livestock production. Integrated control strategies combining targeted grazing management and strategic anthelmintic treatment are recommended to reduce infection risk while maintaining feed availability.