## Overview Theiler’s disease is acute hepatic necrosis, one of the most common causes of acute liver failure in adult horses. It is associated with administration of equine-origin biological products (antitoxin, plasma, serum) and typically appears 4 to 10 weeks later. A pegivirus has been implicated. Signs include acute depression, jaundice, and hepatic encephalopathy with head pressing. Mortality in clinical cases is high (50 to 90 percent). ## Causes Viral hepatitis, often linked to equine-origin biologics. ## Diagnosis History of recent biologic administration, elevated liver enzymes, jaundice, and clinical signs of liver failure. ## Treatment Supportive care only. No specific antiviral therapy. Prognosis is poor once encephalopathy develops. ## Recovery and Prognosis Poor for clinical cases. Horses that survive the acute phase may recover. ## Prevention Judicious use of equine-origin biologics. Modern products have reduced risk.
acute depression; jaundice; hepatic encephalopathy; head pressing; high mortality; often 4 to 10 weeks after equine biologic
## Overview Theiler’s disease is acute hepatic necrosis, one of the most common causes of acute liver failure in adult horses. It is associated with administration of equine-origin biological products (antitoxin, plasma, serum) and typically appears 4 to 10 weeks later. A pegivirus has been implicated. Signs include acute depression, jaundice, and hepatic encephalopathy with head pressing. Mortality in clinical cases is high (50 to 90 percent). ## Causes Viral hepatitis, often linked to equine-origin biologics. ## Diagnosis History of recent biologic administration, elevated liver enzymes, jaundice, and clinical signs of liver failure. ## Treatment Supportive care only. No specific antiviral therapy. Prognosis is poor once encephalopathy develops. ## Recovery and Prognosis Poor for clinical cases. Horses that survive the acute phase may recover. ## Prevention Judicious use of equine-origin biologics. Modern products have reduced risk.
acute depression; jaundice; hepatic encephalopathy; head pressing; high mortality; often 4 to 10 weeks after equine biologic