New Copiparvovirus found in equine tetanus antitoxin

A new parvovirus has been identified which is capable of causing life-threatening liver disease in horses.

Researchers focused on a horse that contracted equine serum hepatitis, also known as Theiler’s disease, after receiving a dose of equine-derived tetanus antitoxin. The horse in Nebraska died 65 days after treatment with the antitoxin.

Dr Thomas Divers and his colleagues identified the previously unknown parvovirus in the serum and liver of the dead horse, as well as in the administered antitoxin.

The equine parvovirus they discovered was genetically analysed and found to be a new species in the genus Copiparvovirus. Other members of the genus Copiparvovirus include parvoviruses that infect pigs, cows, and sea lions, as well as a recently identified virus found in horse cerebrospinal fluid.

The new virus, tentatively known as equine parvovirus-hepatitis (EqPV-H), is more closely related to pig and cow Copiparvovirus than to the only other known horse Copiparvovirus, indicating different evolutionary origins.

The study team, writing in the journal Emerging Infectious Diseases, said their work confirmed that a tetanus antitoxin contaminated with the virus was able to cause infection in two horses.

They also determined that EqPV-H is an endemic infection in horses.

The researchers tested 100 clinically normal adult horses, finding evidence of the virus in the blood of 13 of them. In all, 15 of the horses were seropositive for the virus. This suggests that most horses that become infected with EqPV-H do not develop signs of disease.

The evidence linked the virus with equine serum hepatitis and showed it could be transmitted through contaminated biological products, they said.

Equine serum hepatitis, sometimes called idiopathic acute hepatitis, is a serious and often life-threatening disease of horses. It was first described in 1919 in South Africa by Sir Arnold Theiler.

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