Equine parvovirus hepatitis
In 1918 Theiler’s disease was first described in a group of horses in South Africa after the administration of an equine biological. This disease is characterized by acute hepatic necrosis and fulminant liver failure. Usually, these events are connected to the administration of biological equine substances like plasma, tetanus antitoxin, botulism antitoxin, allogenic stem cells, among others. It has also been described in horses that did not receive biological products and in horses that contacted with other affected animals.
For a long time, there was no specific agent associated with Theiler’s disease, but in 2018 equine parvovirus hepatitis (EqPV-H) was identified in the serum and liver of horses affected with this condition. EqPV-H is an hepatotropic virus, with a worldwide distribution, that has been associated with subclinical and severe cases of hepatitis in horses and consequently the likely culprit for Theiler’s disease.
Clinical signs of Theiler’s disease are icterus, lethargy, inappetence and neurological alterations, this signs usually are associated with and increase of biochemistry parameters and the presence of EqPV-H antibodies (the last have also been reported in asymptomatic horses). Disease will generally develop 4- 10 weeks after contact and outcome is mainly fatal.
All forms of transmission of EqPV-H are not yet fully understood, vectors would be a good theory for the presence of Theiler’s disease in horses that are not in contact with infected animals and have not received biological products, but this type of transmission have yet to be confirmed through literature. EqPV-H should be investigated in cases of hepatitis whether clinical or subclinical, specially in cases with history of administration of biological products. Understanding the transmission further would help to implement prevention measures.
Awareness of risk, both by owners and practitioners, upon the administration of equine biological products is of extreme importance. This is a new virus that has been associated with a fatal disease in horses a lot of research is needed to better understand it and how it affects the equine population, its effects on subclinical cases are still to be investigated.
Ramsauer, S. et al. (2022) ‘Equine Parvovirus Hepatitis”, Equine Veterinary Journal. 53 pp. 886-834
Doi: 10.1111/evj.13477
