Chronic hepatitis in horses with persistent equine hepacivirus infection

Background: Equine hepacivirus (EqHV) is closely related to hepatitis C virus (HCV), which causes persistent infection and chronic hepatitis in people. Information on persistent EqHV infection and hepatitis is limited.
Objectives: We report 19 cases of chronic hepatitis and persistent EqHV infection.

Study design: Mixed retrospective and prospective case series.

Methods: Inclusion criteria were: 1) chronic hepatitis, defined as persistently increased serum liver biomarkers, increased serum liver biomarkers accompanied by histopathologic evidence of chronicity, e.g. fibrosis, or both; 2) positive serum or liver EqHV RT-qPCR; and 3) available liver histopathology. Horses were excluded if they became serum EqHV RT-qPCR undetectable, died, or were euthanized within 6 months of EqHV detection. Liver biopsies were independently reviewed.
Results: Twenty-nine horses met inclusion criteria. Ten were subsequently excluded (two cleared EqHV, 8 died within 6 months). For the remaining 19 horses, median duration of documented hepatitis was 18.4 (range, 5.2-120) months and documented EqHV viremia was 14.8 (range, 6.9-55.6) months. Histopathologic findings mirrored those seen in humans with chronic HCV including fibrosis, lymphocytic infiltrate, lymphoid aggregates, and individual hepatocyte necrosis. One horse was diagnosed with bacterial cholangiohepatitis, and the remainder had no definitive etiologic diagnosis. Bacterial infection, equine parvovirus-hepatitis infection, and equine multinodular pulmonary fibrosis were frequent comorbidities.

Main limitations: A direct causal link between EqHV viremia and hepatitis cannot be made from these data.

Conclusions: Some horses with persistent EqHV infection develop chronic hepatitis and liver failure, with clinical and histopathologic findings resembling HCV in humans.