Chronic hepatitis in horses with persistent equine hepacivirus infection

Chronic hepatitis in horses with persistent equine hepacivirus infection

Equine Vet J. 2025 Dec 25. doi: 10.1111/evj.70124. Online ahead of print.
Authors
Mason C Jager 1 , Daniela Luethy 2 , Samantha Shallop 1 , Jessica Cathcart 2 , Thomas J Divers 3 , Jean-Yin Tan 4 , Erin McConachie Beasley 5 , Philip Johnson 6 , Laurence Leduc 7 , Claire Smith 8 , Camilla Anne Jamieson 9 , K Gary Magdesian 10 , Gerlinde R Van de Walle 11 , Joy E Tomlinson 11
Affiliations

1 Department of Population Medicine and Diagnostic Sciences, Cornell University College of Veterinary Medicine, Ithaca, New York, USA.
2 Department of Clinical Studies, New Bolton Center, School of Veterinary Medicine, University of Pennsylvania, Kennett Square, Pennsylvania, USA.
3 Department of Clinical Sciences, Cornell University College of Veterinary Medicine, Ithaca, New York, USA.
4 Faculty of Veterinary Medicine and Taylor Institute for Teaching and Learning, University of Calgary, Calgary, Alberta, Canada.
5 University of Georgia College of Veterinary Medicine, Athens, Georgia, USA.
6 Equine Internal Medicine and Surgery, College of Veterinary Medicine, University of Missouri, Columbia, Missouri, USA.
7 Faculté de médecine vétérinaire, Université de Montréal, Saint Hyacinthe, Quebec, Canada.
8 Sound Equine Veterinary Hospital, Pouslbo, Washington, USA.
9 Department of Veterinary Clinical Sciences, Purdue University College of Veterinary Medicine, West Lafayette, Indiana, USA.
10 Department of Medicine and Epidemiology, UC Davis School of Veterinary Medicine, Davis, California, USA.
11 Baker Institute for Animal Health, Cornell University College of Veterinary Medicine, Ithaca, New York, USA.

PMID: 41448947
DOI: 10.1111/evj.70124

Abstract

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: To 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 histopathological evidence of chronicity, for example, 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 euthanised 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, the 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. Histopathological 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 histopathological findings resembling HCV in humans.

Keywords: EMPF; cholangitis; dissecting fibrosis; hepatitis C virus; hepatocyte necrosis; horse; liver fibrosis; lymphocytic infiltrate; non‐primate hepacivirus.

© 2025 The Author(s). Equine Veterinary Journal published by John Wiley & Sons Ltd on behalf of EVJ Ltd.