Hepatic Morphological Lesions and Blood Biochemical Evidence of Impaired Metabolism in Wild European Moose (Alces alces) Naturally Infected With Parafasciolopsis fasciolaemorpha

Liver flukes may cause significant pathological changes in domestic and wild ruminants. One such parasite, Parafasciolopsis fasciolaemorpha, reported in European moose (Alces alces), still requires detailed investigation to better understand its pathogenesis and impact on host health. This study aimed to evaluate the gross, histopathological, and biochemical alterations associated with natural P. fasciolaemorpha infection in wild moose inhabiting forests throughout Latvia. Livers from 63 animals were examined, of which 15 (24%) were infected. Infected livers exhibited bile duct thickening and cavities containing trematodes and necrotic debris. Histologically, lesions in infected moose were observed in 82% of examined microscopic fields for portal inflammatory infiltration, 60% for portal fibrosis, and 47% for bile duct proliferation, compared with low frequencies in uninfected animals. Generalized linear mixed models confirmed significant associations between infection and portal inflammation, fibrosis, and bile duct proliferation, whereas bile duct mucous gland hyperplasia did not differ significantly from uninfected moose. Biochemically, infected moose showed reduced serum urea and amylase concentrations, while other hepatic enzyme values did not differ from uninfected controls, indicating mild impairment of hepatic function and possible pancreatic involvement. Fecal examination confirmed the presence of P. fasciolaemorpha eggs and revealed frequent co-infections with gastrointestinal parasites. These findings demonstrate that P. fasciolaemorpha infection in moose is associated with distinctive hepatic lesions and subtle but measurable biochemical alterations, expanding knowledge of this understudied trematode and emphasizing its importance in veterinary pathology and wildlife health.