Hepatic diseases are quite common in equids. In addition to poisonous plants, toxins, parasites, and neoplasms, they can also be caused by bacterial or viral infectious agents. Many aetiologies have already been studied sufficiently, but the cause of the disease known as Theiler’s disease or serum hepatitis has remained largely unexplained for over a century.
You can read more about the update on the aetiology of acute serum in the article by Dr Carla Gerhard: Equine parvovirus – an update on the aetiology of acute serum hepatitis