Borna disease (also called contagious equine encephalitis) is a viral disease that mainly affects horses and sheep. In the past ten years, numerous new Borna viruses have been discovered in birds and reptiles, which can be clearly distinguished from the causative agent of Borna disease in horses.

In parts of Eastern and Southern Germany, Austria, Switzerland and Liechtenstein

Shrews

Via urine, faeces and saliva

Horses show behavioural changes, movement disorders, compulsive movements, empty chewing, lowered head posture, teeth grinding, frightfulness, in the final stage lying down.

There is no therapy

In Austria, the virus has been detected in animals only sporadically so far - in recent years, 4 cases of Bornasch disease have been detected in horses.

In humans, no case of inflammation of the brain (encephalitis) caused by Bornavirus has yet occurred in Austria. In Germany, infections of humans with classical Bornavirus (BoDV-1) were detected for the first time in 2018, resulting in Bornasch disease being classified as a zoonosis.

Shrews are considered to be the natural reservoir for the classical bornavirus (Borna disease virus, BoDV-1): they carry the virus throughout their lives without becoming ill themselves. Over the past ten years, numerous new bornaviruses have been discovered in birds and reptiles, which must be clearly distinguished from the pathogen causing Borna disease in horses. These include the squirrel bornavirus (VSBV-1), which was described in Germany in 2015 among breeders of red squirrels as the cause of central nervous system disorders.

Borna disease (BD) was first described in 1813. It received its name when, in 1894, a large number of cavalry horses fell ill in the town of Borna in Germany. In addition to horses, sheep also frequently contract BD in endemic areas. More recently, cases have also been reported in dogs, cats, cattle, goats, New World camelids and monkeys (experimentally).

Cases in animals in Austria are very rare: in the 1990s, there were two cases in horses and one case in a dog in Vorarlberg. Vorarlberg is considered an area where the classical Bornavirus is endemic. In 1998, a single case was diagnosed in a horse in Styria. In 2015 and 2016, four horses fell ill in a region of Upper Austria. In 2026, a good 10 years after the last confirmed cases, Bornavirus disease with progressive CNS symptoms was again detected in two Upper Austrian horses from the same endemic area (one of which had recently been transferred to Lower Austria).

Clinical symptoms in animals include behavioural changes, movement disorders, compulsive movements, empty chewing, lowered head posture, teeth grinding, nervousness, and, in the terminal stage, inability to rise. Similar symptoms can be caused by other encephalitis pathogens such as West Nile virus, TBE virus, Japanese encephalitis virus, the pathogens responsible for so-called American encephalomyelitis or rabies, as well as by various forms of poisoning.

Although Borna disease is a zoonosis, it is not currently classified as a notifiable animal disease under the Animal Health Act (AHL). However, in cases of clinical suspicion of encephalitis or in cases of progressive forms with a poor prognosis or fatal outcome, blood samples or the CNS of the affected animals should nevertheless be sent to the National Reference Laboratory for further investigation. Due to the zoonotic potential of most pathogens to be considered in the differential diagnosis, the head (in compliance with biosecurity measures) should be removed and sent for analysis.

Information from the Robert Koch Institute

Information from the Friedrich Loeffler Institute