The pathology of natural Fasciola hepatica infection in cattle.

The pathology of bovinc livers during the parenchymal and chronic phases of natural Fasciola hepatica infections is described. Immature infections occurred from September to the middle of January. Significant changes of the hepatic parenchyma caused by immature flukes occurred in association with large migrational tracks. The changes included frequent thrombosis and haemorrhages, extensive disintegration and coagulative necrosis of hepatic cells, and abundant infiltrates of inflammatory cells. In chronic infections the proliferation and destruction of the mucosa of main bile ducts were pronounced. Normal mast cells were lacking in the portal areas surrounding fresh migrational tracks. In chronically infected livers mast cells occurred in great numbers.