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Chronic hepatitis in horses with persistent equine hepacivirus infection.
Abstract: 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. Objective: To report 19 cases of chronic hepatitis and persistent EqHV infection. Methods: 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. Conclusions: 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.
© 2025 The Author(s). Equine Veterinary Journal published by John Wiley & Sons Ltd on behalf of EVJ Ltd.
Publication Date: 2025-12-25 PubMed ID: 41448947PubMed Central: PMC12892389DOI: 10.1111/evj.70124Google Scholar: Lookup The Equine Research Bank provides access to a large database of publicly available scientific literature. Inclusion in the Research Bank does not imply endorsement of study methods or findings by Mad Barn.
- Journal Article
Summary
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Overview
- This study reports on 19 horses with chronic liver inflammation (hepatitis) and persistent infection by equine hepacivirus (EqHV), a virus related to human hepatitis C virus (HCV).
- The research characterizes the clinical and pathological features of EqHV infection and compares them to human HCV infection.
Background
- Equine hepacivirus (EqHV) is a virus that infects horses and is closely related to hepatitis C virus (HCV), which causes chronic liver disease in humans.
- While HCV is well studied and known to cause persistent infections leading to chronic hepatitis and potentially liver failure, less is known about EqHV’s effects in horses.
- The study aimed to investigate cases of chronic hepatitis in horses that also had persistent EqHV infection to better understand this relationship.
Study Objectives
- To identify and describe cases of chronic hepatitis in horses with persistent EqHV infection.
- To analyze liver biopsy histopathology in infected horses and compare these findings with known features of human chronic hepatitis C infection.
- To assess whether persistent EqHV infection is associated with chronic liver disease in horses.
Methods
- The research design combined retrospective (review of past cases) and prospective (new case identification) approaches.
- Inclusion criteria included:
- Evidence of chronic hepatitis: ongoing elevated liver enzymes or biopsy showing fibrosis or other chronic features.
- Positive detection of EqHV RNA in serum or liver by RT-qPCR, confirming infection.
- Availability of liver histopathology samples for independent review.
- Horses were excluded if they cleared the virus or died/euthanized within 6 months of detection to focus on persistent infection cases.
- Liver biopsies were independently examined by pathologists to determine histopathological changes.
Results
- A total of 29 horses initially met the inclusion criteria; after exclusions, 19 horses remained for final analysis.
- The median duration of reported hepatitis was about 18.4 months, and EqHV viremia persisted for a median of 14.8 months, indicating relatively long-term infection and inflammation.
- Liver histopathology findings included:
- Fibrosis (scarring of liver tissue)
- Lymphocytic infiltrate (immune cells present in liver tissue)
- Lymphoid aggregates (collections of immune cells)
- Individual hepatocyte (liver cell) necrosis (cell death)
- These histological features closely resemble the liver changes seen in people with chronic HCV infection.
- One horse was diagnosed with bacterial cholangiohepatitis (bacterial infection affecting bile ducts and liver); the rest had no clear alternative cause for hepatitis.
- Frequent comorbidities observed included:
- Bacterial infections
- Equine parvovirus-hepatitis infection
- Equine multinodular pulmonary fibrosis (a lung condition)
Conclusions
- The study could not definitively establish a direct causal link between EqHV viremia and chronic hepatitis because of observational nature and complex comorbidities.
- Nonetheless, some horses with persistent EqHV infection developed chronic hepatitis and eventual liver failure.
- The clinical symptoms and liver tissue changes in these horses resembled the chronic hepatitis caused by HCV in humans.
- These findings suggest EqHV may be a relevant viral agent in equine chronic liver disease and serve as a useful comparative model for human HCV infection.
Implications and Future Directions
- This research supports further investigation into the role of EqHV in causing chronic hepatitis in horses.
- Understanding EqHV pathogenesis may aid in developing diagnostic, therapeutic, or preventive approaches targeting equine liver disease.
- Because of similarities with human HCV infection, EqHV-infected horses could provide a valuable comparative model to study hepacivirus infections and liver disease progression.
- Larger and controlled studies are needed to clarify causal relationships and mechanisms of EqHV-mediated liver injury.
Cite This Article
APA
Jager MC, Luethy D, Shallop S, Cathcart J, Divers TJ, Tan JY, Beasley EM, Johnson P, Leduc L, Smith C, Jamieson CA, Magdesian KG, Van de Walle GR, Tomlinson JE.
(2025).
Chronic hepatitis in horses with persistent equine hepacivirus infection.
Equine Vet J, 58(2), 444-457.
https://doi.org/10.1111/evj.70124 Publication
Researcher Affiliations
- Department of Population Medicine and Diagnostic Sciences, Cornell University College of Veterinary Medicine, Ithaca, New York, USA.
- Department of Clinical Studies, New Bolton Center, School of Veterinary Medicine, University of Pennsylvania, Kennett Square, Pennsylvania, USA.
- Department of Population Medicine and Diagnostic Sciences, Cornell University College of Veterinary Medicine, Ithaca, New York, USA.
- Department of Clinical Studies, New Bolton Center, School of Veterinary Medicine, University of Pennsylvania, Kennett Square, Pennsylvania, USA.
- Department of Clinical Sciences, Cornell University College of Veterinary Medicine, Ithaca, New York, USA.
- Faculty of Veterinary Medicine and Taylor Institute for Teaching and Learning, University of Calgary, Calgary, Alberta, Canada.
- University of Georgia College of Veterinary Medicine, Athens, Georgia, USA.
- Equine Internal Medicine and Surgery, College of Veterinary Medicine, University of Missouri, Columbia, Missouri, USA.
- Faculté de médecine vétérinaire, Université de Montréal, Saint Hyacinthe, Quebec, Canada.
- Sound Equine Veterinary Hospital, Pouslbo, Washington, USA.
- Department of Veterinary Clinical Sciences, Purdue University College of Veterinary Medicine, West Lafayette, Indiana, USA.
- Department of Medicine and Epidemiology, UC Davis School of Veterinary Medicine, Davis, California, USA.
- Baker Institute for Animal Health, Cornell University College of Veterinary Medicine, Ithaca, New York, USA.
- Baker Institute for Animal Health, Cornell University College of Veterinary Medicine, Ithaca, New York, USA.
MeSH Terms
- Animals
- Horses
- Horse Diseases / virology
- Horse Diseases / pathology
- Male
- Hepacivirus / isolation & purification
- Female
- Retrospective Studies
- Prospective Studies
- Hepatitis C, Chronic / veterinary
- Hepatitis C, Chronic / virology
- Hepatitis C, Chronic / pathology
- Hepatitis, Chronic / veterinary
- Hepatitis, Chronic / virology
- Hepatitis, Chronic / pathology
Grant Funding
- 2022-67015-36343 / National Institute of Food and Agriculture
- K08AI141767 / National Institute of Allergy and Infectious Diseases
- K08AI63401 / National Institute of Allergy and Infectious Diseases
- T32ODO011000 / NIH HHS
- K08 AI141767 / NIAID NIH HHS
- K08 AI163401 / NIAID NIH HHS
- T32 OD011000 / NIH HHS
Conflict of Interest Statement
The authors declare no conflicts of interest.
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