Acute Fascioliasis as a Leading Cause of Mortality in Free-Ranging Flocks of Domestic Sheep in Babol Countryside, Mazandaran Province, Iran: A Case Report.

In July 2021, the School of Veterinary Medicine at Amol University of Special Modern Technologies was informed of high mortality within a sheep flock. Out of 200 animals, 24 sheep died within a few days. Due to the rapid deaths, poisoning was initially suspected but ruled out after clinical observation, sampling, and necropsy. A full herd assessment was performed, and blood and fecal samples were collected from lambs and adults for laboratory analysis. Blood samples were drawn via jugular venipuncture; fecal samples were examined using the Modified McMaster technique to detect helminth eggs or protozoan oocysts. For hematological and biochemical evaluation, blood was divided into EDTA and plain tubes. Serum analysis revealed a significant elevation in AST levels, indicating hepatic tissue damage associated with the parenchymal migration of juvenile Fasciola hepatica during acute fascioliasis. Infected sheep showed a marked reduction in serum SOD activity (P<0.001) and a significant increase in MDA levels (P<0.001) compared with non-infected animals, reflecting oxidative stress. These findings suggested that environmental and climatic conditions at the time favored the spread of fascioliasis. Considering the zoonotic potential and widespread occurrence of F. hepatica, effective control and preventive strategies are essential. Recommended measures include wetland drainage, strategic deworming, and controlling snail and slug populations to limit transmission.