Abstract
This paper describes briefly the normal ultrastructure of bile-duct epithelial cells in cattle and the main ultrastructural alterations produced in them by chronic infection with Fasciola hepatica. The studies showed only inconsiderable abnormalities in the ultrastructure of the epithelium in infections of a low degree as also during the recovery phase of the disease. On the other hand, in heavily infected livers pronounced ultrastructural alterations were seen in the surface epithelium of the main intrahepatic bile ducts invaded by the flukes. In such areas the intercellular spaces were filled with dense homogeneous material, and intact desmosomes and junctional complexes were not regularly seen, which indicates that foreign material may leak into the bile. The extracellular material was probably composed of albumin, and the significance of the present results regarding the etiology of hypoalbuminaemia during chronic fascioliasis is discussed.