Non-neoplastic liver disease associated with chronic ground squirrel hepatitis virus infection.

We examined 95 ground squirrels to compare the histological appearance of liver sections from animals that were chronically infected with ground squirrel hepatitis virus (GSHV) (n = 29), uninfected (n = 42), or had recovered from infection (n = 24). We studied the effects of long-term infection because these animals had been infected with GSHV for up to 10 years. Chronic infection generally produced a mild, persistent hepatitis characterized by light lymphocytic and plasmacytic portal infiltrates with occasional individual necrotic hepatocytes and small aggregates of Kupffer cells or mononuclear inflammatory cells in the parenchyma. In a few of the portal tracts from each of the more inflamed livers (grade 2), the inflammatory infiltrate penetrated the limiting plate and extended into the adjacent parenchyma. Hepatitis (grades 1 or 2) was detected more often in chronically infected animals (17 of 29) than in recovered (4 of 24) or uninfected ground squirrels (7 of 42). Fibrosis was generally not increased, but fine strands of collagen extended from the portal tracts and central veins into the parenchyma of about one quarter of the infected and recovered animals. Cytoplasmic pigment accumulation and variation in the size of hepatocyte nuclei appeared to be related to aging, not infection. Serum levels of aspartate and alanine transaminases (AST and ALT) were mildly elevated in samples from seven infected animals compared with seven control animals. Despite many years of chronic infection, liver injury was similar to that reported in previous studies on animals infected for shorter intervals, indicating that liver injury is not progressive in GSHV-infected ground squirrels.