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Hepatitis in Horses

Liver Inflammation in Horses


Hepatitis is defined as inflammation of the liver. A vital organ that performs numerous metabolic functions that are necessary for life, much of the liver can shut down before the effects of the disease are apparent in horses. This also means that by the time the symptoms of hepatitis are displayed, sometimes the damage is too severe to start treatment. Therefore, it is important to bring your horse to a veterinarian immediately if you see any of the symptoms mentioned below.


Symptoms and Types


Hepatitis can occur acutely, as with ingestion of certain toxins, or can develop slowly, as with some underlying infections. However once the initial damage begins, any or all of following signs may appear:


    • Depression
    • Anorexia
    • Colic (abdominal pain)
    • Weight loss
    • Yellowing of the mucous membranes (jaundice)
    • Fluid accumulation (edema)
    • Neurologic signs such as head pressing, incoordination, blindness, drowsiness, confusion
    • Photosensitization
    • Diarrhea




There are several causes of hepatitis in horses. Bacteria such as Clostridia can cause liver inflammation, and there are a few viruses that can cause it as well. There are also numerous toxins that can cause hepatitis, mostly found in certain plants such as ragwort, whitebush, and sometimes ryegrass. Another cause of hepatitis is called serum sickness. This occurs when a horse is exposed to a therapeutic agent that contains equine serum. Antibodies against the foreign horse proteins then destroy the horse’s own liver.




A presumptive diagnosis of liver disease can be made by your veterinarian based on your horse’s clinical signs; however, additional laboratory tests will need to be done, such as blood work and perhaps even imaging such as abdominal ultrasound. Liver biopsies can also be performed to aid with the diagnosis.