Ground squirrel hepatitis virus (GSHV) infection and hepatocellular carcinoma in the Canadian Richardson ground squirrel (Spermophilus richardsonii)

Abstract

Sera and livers from 40 Richardson ground squirrels were examined for evidence of ground squirrel hepatitis virus (GSHV) infection and hepatocellular carcinoma. Twenty-five sera were obtained from fully grown adult ground squirrels and 15 from young ground squirrels estimated to be between 6-8 weeks of age. All animals had been caught in the wild and had spent less than 1 month in captivity. Sixteen sera (40%) had at least one serologic marker of GSHV (2 with GSHV surface antigen, 3 GSHV core antigen, 5 GSHV antibody to core antigen and 11 GSHV antibody to surface antigen). Two cases of hepatocellular carcinoma were detected, both in adult ground squirrels. Tumour tissue and adjacent normal liver tissue were negative for GSHV surface and core antigen by direct immunofluorescence in both livers and negative for GSHV-DNA by molecular hybridization in the one tumour examined. These results indicate that: A) GSHV is geographically more widespread than previously considered; B) viral transmission occurs early in life, probably via the vertical route; and C) hepatocellular carcinoma is a relatively common finding in these animals while still in their wild state. Any causal relationship between hepatocellular carcinoma and GSHV infection in these animals, however, has yet to be demonstrated.