Experimentally induced Fasciola hepatica infection in white-tailed deer. II. Pathological features

Six white-tailed deer (Odocoileus virginianus) and six sheep were inoculated with metacercariae of Fasciola hepatica. Two animals of each species were given 100, 500 or 2500 metacercariae. One animal in each inocluated group was killed and examined at six weeks postinoculation and the remainder at 15 weeks postinoculation. At six weeks postinoculation the parietal surface of the livers from inoculated deer was covered with gray fibrous plaques and rust colored patches. Fibroplasia with mononuclear cell infiltration characterized Glisson's capsule on the parietal surface. Granulomas were found in the hepatic parenchyma and on the dorsal surface of the lung. Fresh and healing tracks were occasionally found in the liver. In the sheep fibrinous exudate and numerous subcapsular tracks were found on both surfaces of the liver. Inflammatory changes in portal areas and numerous fresh and healing tracks in the hepatic parenchyma were prominent features. At 15 weeks postinoculation inflammatory changes in Glisson's capsule of inoculated deer were less marked than at six weeks but portal fibrosis and hyperplasia of bile duct epithelium were more advanced. A zone of hemorrhage surrounded ducts that contained mature F. hepatica in one deer. The livers from the sheep were rough, pitted and covered with fibrous tags and adhesions to the diaphragm and greater omentum were common. Hemorrhagic tracks were common in the sheep given 500 and 2500 metacercariae. Portal fibrosis and hyperplasia of bile duct epithelium were seen in the sheep (100 metacercariae) that harbored mature F. hepatica.