Equine hepacivirus (EqHV) is a highly prevalent virus with the potential to cause fatal chronic hepatitis in horses. It most commonly causes resolving subclinical hepatitis. However, we have recently observed EqHV-infected horses with severe chronic hepatitis. This condition strongly resembles liver disease caused by the closely related hepatitis C virus (HCV) in humans. Given this increased recognition of the health burden of EqHV infection in horses, our long-term objective is to reduce and/or prevent transmission and disease caused by EqHV.

Our specific hypothesis is that EqHV is readily transmitted among horses and can cause chronic hepatitis and liver failure during persistent infection. To test this, we will perform epidemiologic and experimental modeling of EqHV infection and transmission (Aim 1), characterize the clinical condition of chronic EqHV hepatitis by prospective case series and retrospective histopathologic review of banked liver biopsies (Aim 2), and identify risk factors of persistence and severe disease including age, sex, host immune response, and viral genetics (Aim 3).

The significance of this work is to develop a foundation for EqHV disease diagnosis, prevention, and control. Determining the epidemiology, transmission and pathogenic burden of the virus, and risk factors for severe disease, can drive future development of vaccines, treatments, and management strategies, including possible governmental regulations on equine biologic products, as has been done for the other recently discovered liver pathogen, equine parvovirus-hepatitis. As such, this work can contribute to an overall understanding of and reduction in cases of transmissible liver disease in horses with hitherto unknown etiology.