Theiler's disease

Theiler's disease is a viral hepatitis that affects horses. It is one of the most common cause of acute hepatitis and liver failure in the horse. Theiler's disease is a viral hepatitis that affects horses. It is one of the most common cause of acute hepatitis and liver failure in the horse. There is a rapid onset of clinical signs over the period of 2–7 days, beginning with anorexia, lethargy, and hyperbilirubinemia (icterus and discolored urine). Signs of hepatic encephalopathy (ataxia, blindness, aggression, and coma) and fever can also occur. Other signs include photodermatitis, hemorrhagic diathesis, dependent edema, and colic. The reason for colic is unknown, but is thought to be due to rapid decrease in the size of the liver, and the increased risk of gastric impaction. Rarely, weight loss can occur. The most current theory is a result of a recent study that suggests it is caused by a pegivirus, referred to as Theiler's disease-associated virus (TDAV). Eight horses that had received prophylactic botulinum antitoxin and developed subsequent signs of Theiler's disease were subjected to a test for a viral infection based on RNA sequencing techniques. When TDAV was found, the original source of virus (the antitoxin) was injected into 4 additional healthy horses, with one displaying increased liver enzymes and all 4 having increased levels of TDAV, showing that the virus can be spread by inoculation. Measuring levels of virus in the originally infected horses has shown that the disease can become chronic, with some horses displaying low virus levels one year after initial infection. All horses that were initially negative remained so, suggesting that the virus is poorly transmitted horizontally.