Hepatic fibrosis in rabbits infected with Japanese and Philippine strains of Schistosoma japonicum.

Symmers' clay pipestem fibrosis of the liver was produced by Schistosoma japonicum infection in the rabbit. Gross and microscopic portal fibrosis and portal vascular lesions resembled those in hepatosplenic schistosomiasis in man. Portal obstruction caused dilation of portal-systemic collateral veins but only minimal portal hypertension. The rapidity of development and prevalence of Symmers' fibrosis were related to the intensity of the schistosome infection. A mixed macronudular and micronodular cirrhosis of the liver was also present in most animals with Symmers' fibrosis, and other differences from the disease in man were present as well. Hepatic fibrosis regressed after the 30th week of infection, as judged from gross and microscopic observations and from measurement of hepatic collagen. The prevalence of Symmers' fibrosis and cirrhosis also decreased after the 30th week in the less heavily infected rabbits. The S. japonicum-infected rabbit is an imperfect model of human Symmers' fibrosis, but the rabbit is the only experimental model available other than the schistosome infected chimpanzee. The rapid production of severe fibrosis without the use of hepatotoxic agents, and the reversibility of the lesions, make this model of general interest for the study of hepatic fibrosis.