A new parvovirus has been identified in horses that can cause life-threatening liver disease. A horse in Nebraska contracted equine serum hepatitis (liver disease), also called Theiler's disease, after having an equine-derived tetanus antitoxin administered. He died 65 days after treatment, reports HorseTalk.
Dr. Thomas Divers and colleagues identified the unknown parvovirus in the liver and serum of the dead horse, as well as in the antitoxin that was administered. The parvovirus they discovered was found to be a new species in the genus Copiparvovirus. Other strains of parvoviruses infect cows, pigs, sea lions and horses (which was recently found in equine cerebrospinal fluid). The researchers reported on their findings in Emerging Infectious Diseases.
The newest virus is tentatively known as equine parvovirus-hepatitis (EqPV-H), and is more-closely related to the parvovirus found in cows and pigs than the other equine version, which indicates that the equine viruses have different evolutionary origins.
The team said that their findings confirm that the tentanus antitoxin was contaminated with the virus and infected two horses. It was also determined that EqPV-H is an endemic infection in horses.
For the study, researchers tested 100 adult horses that were clinically normal and found the virus in the blood of 13 horses. Fifteen of the horses tested seropositive for the virus, which suggests that most horses that are infected with EqPV-H don't develop any signs of the disease.
The research showed that the virus could be transmitted by contaminated biological products and is linked with liver disease, which is a serious and potentially life-threatening. The research team notes that parvoviruses are common and can have various effects on their hosts, not always causing disease. Parvovirus hepatitis in other species is rare.
Overall, the incidence of serum hepatitis in horses that get a tetanus antitoxin is low, but it is the most commonly reported blood product associated with the disease. Commercial tetanus antitoxin is a heat-treated, inactivated virus with preservatives added. The researchers reported that animal parvoviruses are very resistant to heat inactivation.
The study suggests that the majority of horses that become infected with the virus don't develop clinical signs of disease. The researchers said that studies including horses living in different geographic areas are needed to determine the true genetic diversity and prevalence of the virus. Additional study is also needed to determine why some horses develop equine serum hepatitis and others do not.
Read more at HorseTalk.
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