Bornaviruses BoDV-1 can be threatening even for healthy people

Dangerous brain inflammation: Bornavirus can also be deadly for humans

A study by German researchers has shown that the classic bornavirus (BoDV-1), which is known from diseases in horses and sheep, can also cause fatal brain inflammation in healthy people. Earlier studies had shown that the pathogen can be dangerous for humans.

Deadly bornavirus infections in Germany

A few months ago it had been reported that fatal viral Bornavirus infections had occurred in Germany for the first time. The infection, which can cause inflammation of the brain, occurred in a total of five individuals, three of whom were donor organ donors. Now, a study by researchers at the University Hospital Erlangen has shown that the pathogen can also be life-threatening for healthy people.

German researchers have discovered that Bornavirus, which is known to cause disease in horses and sheep, can cause lethal brain inflammation in healthy people. (Image: famveldman / fotolia.com)

Disease cases were clearly triggered by the bornavirus

According to a study published in the journal "New England Journal of Medicine", the classic bornavirus (BoDV-1), which is known from diseases in horses and sheep, can also cause fatal brain inflammation in healthy people.

"The fatal cases we examined showed the clinical picture of a severe brain inflammation, which was clearly triggered by a Bornavirus infection," said Prof. Dr. med. Armin Ensser from the Virological Institute of the University Hospital Erlangen, in a statement.

According to the information, the investigated disease closely resembles the Borna s disease in horse and sheep as well as the very rare bornavirus infections in owners of exotic bunnies in Germany.

Pathogen spread in certain parts of Europe

According to the current state of knowledge, the causative Borna virus is regionally limited in parts of eastern and southern Germany, Austria, Switzerland and Liechtenstein.

"In patients with severe neurological diseases, the Borna virus should therefore be considered as a possible pathogen, especially in these risk areas," said Prof. Ensser.

"The dark figure of Bornavirus infections in fatal brain inflammation is unknown because the infection has not been considered in routine investigations."

Now further research is to clarify, among other things, how common Bornavirus infections are in humans, how the virus can be diagnosed in time and the fatal infection can be prevented.

According to the experts, there is currently no approved antiviral therapy.

Shrews as a possible source of infection

According to the scientists, the "heated head disease of the horses", which is triggered by the virus of Borna's disease, was first described in 1813.

The disease received its name in 1894, when a whole stable full of cavalry horses in the city of Borna (Saxony) fell ill.

The natural reservoir of the Bornavirus is the Feldspitzmaus.

It was previously known that the virus is excreted by shrews via the urine and saliva and occasionally transmitted to other mammals - so-called spoilers of this virus - which can then lead to Borna's disease.

Especially horses and sheep are affected. While infected field-shrews show no signs of disease, the virus attacks the central nervous system in the vertebrates, and extensive damage to the brain occurs, probably due to the attack of the body's own immune cells.

Transmission of the virus from infected horses or sheep among themselves or to other mammals has not been demonstrated. The virus is not excreted by the Fehlwirten and is hardly detectable in their blood.

Detection of virus-specific antibodies clearly confirmed

After two patients without known risk factors and despite intensive treatment at the Neurological Clinic of the University Hospital Erlangen had died of severe brain inflammation of unknown cause, had the research team of neuropathologists, neurologists, pathologists and virologists led by Prof. Ensser their tissue samples using modern next-generation -Sequencing method investigated.

For this purpose, the RNA sequences of millions of RNA molecules were determined and compared bioinformatic with sequence databases of known pathogens.

As a result, scientists in the brain of one of the deceased patients identified large amounts of the genetic material of a virus. The nucleic acid sequence of this virus was clearly associated with the classic Borna Disease Virus 1 (BoDV-1).

In subsequent methodologically independent investigation methods, the diagnosis of Bornavirus infection by antigen detection using classical immunohistochemistry, RT-PCR (reverse transcriptase polymerase chain reaction) and the detection of virus-specific antibodies in the patient's serum could be clearly confirmed.

Virus detected in recipients of donor organs

The Bornavirus could also be detected by three other donor organ donors of a postmortem organ donor, which is considered a virus carrier.

Two of the immunosuppressed organ recipients died as the third survived with severe brain damage.

The cases studied are not confirmation of past published studies on the prevalence of BoDV-1 infections in humans and certain neuropsychiatric disorders.

"In particular - except in the brain - no virus and no viral components in other tissues and body fluids were detectable, so that transmission of the virus can be excluded via normal interpersonal contacts," said Prof. Ensser.

All patients and organ donors were reported to be from one of the known areas of BoDV-1 distribution.

Controversy over the danger of the virus

In the past, there was a scientific controversy about the virus and its dangerousness.

The beginning of the 1990s started research at the Robert Koch Institute (RKI) on possible Bornavirus infections in humans was discontinued in 2005.

At that time it was said that despite many years of efforts, no reliable indication of a danger to humans was found.

Suspected bornavirus detection in human specimens was later attributed to contamination in the laboratory.

The topic was also receiving much attention because some of the scientists described bornavirus as a factor in the development of diseases such as depression and schizophrenia.

However, according to the Society for Virology (GfV), "there is still no scientific evidence to support the sometimes-published theory that a large proportion of the population is infected with the virus and that there are a number of neurological and psychiatric disorders".

The experts of the GfV see a high demand for further investigation of the virus, in order to clarify open questions regarding distribution, transmission paths, early diagnosis and therapy of the virus. (Ad)