Experimental hepatic fibrosis due to Capillaria hepatica infection (differential features presented by rats and mice).

Rats and mice are among the most susceptible hosts for the helminth Capillaria hepatica. More information on the similarities and differences between the hepatic pathology presented by these two parasite hosts are needed, since they may represent good models for the study of hepatic fibrosis. Early changes are similar for both hosts and are represented by necro-inflammatory lesions around dead parasites and their eggs and diffuse and intense reactive hepatitis. Although worms remain alive longer in mice than in rats, hepatic changes are more rapidly and deeply modulated in the former, even leading to almost complete disappearance of fibrosis. As for the rats, the modulation of the focal lesions is followed by the formation of septal fibrosis, a process where fine and long fibrous septa appear connecting portal spaces and central veins in such a way as to form a final morphologic picture of cirrhosis. Hepatic functional changes usually present good correlations with the morphologic findings at the different phases of the infection evolution. Therefore C. hepatica infection in rats and mice represent two different models of hepatic fibrosis and these differences, if properly known and understood, can be explored to answer different questions regarding several aspects of hepatic fibrosis.