Equine serum hepatitis, also called Theiler's disease, can threaten the life of adult horses by compromising their liver. First described in the early 1900s as highly fatal liver failure that occurred after an equine antiserum for African Horse Sickness was given, more-recent cases of the disease in North America have been associated with tetanus antitoxin and commercial plasma products with an equine origin.
Affected horses tend to exhibit neurologic signs like stumbling and headpressing, as well as jaundice. In 70 percent of the cases, the affected horses die.
It has long been suspected that a virus was responsible for the disease and recently a new equine parvovirus was discovered in a deceased horse that had serum hepatitis; it was also found in the biologic products it had received. Experimental horses were given the biologic products and they also developed the virus and liver disease.
Another liver-impacting virus has been discovered in horses that is similar to human hepatitis C. Called non-primate hepacivirus (NPHV), the disease is mild. Horses that have both NPHV and equine parvovirus can be healthy carriers, so the USDA Center for Veterinary Biologics now requires that all licensed equine blood products must test free from both equine parvovirus and NPHV. This requirement should eliminate most of the blood product-associated cases of hepatitis.
Read more at Equine Disease Quarterly.
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