Caring for the Horse’s Liver: What to Know About Hepatitis Viruses

Equine hepatitis viruses can pose a serious risk to a horse’s health, but with proper management and preventive measures, the impact can be minimized.
Sick horse in stall, horse with liver disease/hepatitis.
EqPV-H is associated with acute hepatitis, a more sudden form of liver inflammation that can frequently present with severe clinical signs. | Adobe Stock

Equine hepatitis viruses are a group of viruses that can affect horses’ liver health. While some infections might go unnoticed, others can lead to significant health concerns. The two viruses currently identified as liver-specific pathogens are equine hepacivirus (EqHV) and equine parvovirus-hepatitis (EqPV-H). 

What Are EqHV and EqPV-H? 

EqHV is a virus that primarily causes chronic hepatitis in horses. Most horses infected with EqHV clear the virus within 20 weeks without showing any clinical signs. However, about 20% of cases develop chronic hepatitis, which can persist for more than six months. This chronic condition can present as subclinical or with signs of liver disease, such as jaundice, lethargy, or poor appetite. 

EqPV-H is associated with acute hepatitis, a more sudden form of liver inflammation that can frequently present with severe clinical signs. This virus has been linked to Theiler’s Disease, a condition that can cause rapid liver failure in horses. 

EqHV is ubiquitous, and 20-40% of horses have circulating antibodies against the virus without signs of liver disease; only a small number of horses develop clinical disease. This suggests that exposure to the virus is frequent, but in most cases the horse’s immune system can successfully combat the virus without causing visible signs of disease. Similarly, approximately one-third of horses have been exposed to EqPV-H. While these infections often go unnoticed and do not cause clinical signs, a small percentage of cases can result in severe, potentially life-threatening liver disease, sometimes affecting several horses simultaneously as an outbreak. 

Horses can contract these viruses through contaminated biologics, such as plasma or stem cells, as well as through natural horizontal transmission. For example, EqPV-H can pass through nose-to-nose contact. Natural transmission routes still have to be explained further. 

How Are These Viruses Diagnosed? 

Diagnosing these viruses involves a combination of blood testing and liver biopsies. For EqHV, veterinarians may use serial biochemistry and PCR tests to monitor viral load and liver enzyme activity. Chronic cases are confirmed when viremia (presence of the virus in the blood) and hepatitis persist for more than six months. For EqPV-H, liver biopsies are commonly used to confirm the diagnosis. 

Managing Infected Horses 

Managing horses infected with EqHV or EqPV-H requires supportive care and careful attention to biosecurity. 

For EqPV-H, infected horses should be isolated for four to eight weeks after the onset of hepatitis. Horses that test positive for the virus can be housed together, but they must be kept separate from uninfected horses until the viral load decreases sufficiently to make transmission unlikely. Regular screening of all horses in the herd is recommended to identify new infections early. Typically, horses infected with EqHV do not require isolation due to the widespread distribution of the virus among non-clinically infected horses. However, monitoring the horse’s health and liver function is essential. With both viruses, severely ill horses might need to be referred to a veterinary care facility for specialized treatment. Routine monitoring of serum biochemistry and signs of disease progression are important. 

Prevention Tips  

While no specific antiviral treatments or vaccines are currently available for these viruses, prevention efforts emphasize the importance of quality control in equine biologic products. It is crucial to use biologics that have been tested and confirmed as free from these viruses to minimize the risk of transmission. 

Research and Future Directions 

Research on equine hepatitis viruses is moving forward quickly, helping us better understand how these viruses cause disease and explore potential treatment options. Another important research focus is investigating how environmental factors and potential reservoirs/carriers might spread these viruses. Although small amounts of viral genetic material have been found in stable flies (Stomoxys calcitrans), it is still unclear if this represents an infectious dose of virus or if stable flies can actually transmit the disease. Clarifying these transmission pathways could lead to improved prevention strategies. 

Early pilot studies on new vaccines for EqHV are already in progress, paving the way for more effective ways to protect horses in the future. 

Conclusion 

Equine hepatitis viruses can pose a serious risk to a horse’s health, but with proper management and preventive measures, the impact can be minimized. Awareness of these viruses, their modes of transmission, and the importance of early diagnosis can help veterinarians take proactive steps to protect their patients.

Stay in the know! Sign up for EquiManagement’s FREE weekly newsletters to get the latest equine research, disease alerts, and vet practice updates delivered straight to your inbox.

 

categories
tags
Trending Articles
Young woman riding a horse on the green field
Sodium Hyaluronate’s Effects on Equine Joint Range of Motion  
stifle-rads
Equine Stifle Radiology Tricks and Surprises
Tablets Pills Horse
Using the Right Medications to Manage Chronic Pain in Horses
Stablelab
Understanding the Typical Serum Amyloid A Response Curve: The Key to Interpreting Stablelab Results
Newsletter
Get the best from EquiManagement delivered straight to your inbox once a week! Topics include horse care, disease alerts, and vet practitioner updates.

"*" indicates required fields

Name*
Country*

Additional Offers

Untitled
This field is for validation purposes and should be left unchanged.
EquiManagement
Privacy Overview

This website uses cookies so that we can provide you with the best user experience possible. Cookie information is stored in your browser and performs functions such as recognising you when you return to our website and helping our team to understand which sections of the website you find most interesting and useful.