Bornaviruses cause a lethal form of encephalitis, called borna disease, in horses and sheep. To date there have been only a few reported cases in Austria. Recently, however, several horses from the same area of Upper Austria contracted the disease in a span of just two years. And tests conducted on local shrews, the only known reservoir host for the virus, confirmed the suspicion of a local viral reservoir.

Clinical signs of Borna disease in horses and sheep include behavioral disturbances and disorientation. The causative agent, the bornavirus, is harmless in people but triggers a lethal brain and the spinal cord infection in affected animals. The virus is transmitted exclusively via a reservoir host: the protected bicolored white-toothed shrew. Infected shrews are lifelong, but asymptomatic, bornavirus carriers.

Despite a declining number of cases, occasional sporadic outbreaks of the disease have been documented in Central Europe with the exception of Austria. Now researchers from Vetmeduni Vienna and the Austrian Agency for Health and Food Safety (AGES) have confirmed for the first time an outbreak of borna disease in a previously unaffected area. Within a period of just two years, four horses in Upper Austria contracted the disease in locations no more than 17 kilometers (about 10.5 miles) apart. Local bicolored white-toothed shrews, as well as one common shrew, tested positive for the virus. The bornaviruses the researchers found, however, were, genetically speaking, distantly related to the viruses found in neighboring regions like the state of Bavaria, in Germany.

Local Vets Recognize First Outbreak in Upper Austria

The first indication of a possible borna disease outbreak came from two vigilant local veterinarians. They diagnosed a neurologic condition among four horses in Upper Austria and suspected that bornaviruses could be responsible. Examinations of the afflicted horses confirmed the diagnosis and the suspicion