Bornaviruses BoDV-1 can become a threat even to healthy people

Bornaviruses BoDV-1 can become a threat even to healthy people

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Dangerous inflammation of the brain: Bornavirus can also be fatal to humans

A study by German researchers has shown that the classic Bornavirus (BoDV-1) 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.

Fatal Bornavirus infections in Germany

A few months ago it had been reported that fatal Bornavirus infections had occurred in humans for the first time in Germany. The infection, which can trigger inflammation of the brain, was reported to affect a total of five people, three of whom were recipients of donor organs from the same donor. A study by researchers at the University Hospital Erlangen has now shown that the pathogen can also be life-threatening for healthy people.

Cases of illness were clearly triggered by the Bornavirus

According to a study published in the New England Journal of Medicine, the classic Bornavirus (BoDV-1), 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 severe brain inflammation, which was clearly caused by a Bornavirus infection," explained Prof. Dr. Armin Ensser from the Virological Institute of the University Hospital Erlangen, in a message.

According to the information, the examined clinical picture is very similar to the Bornasch disease in horses and sheep and with the very rare Bornavirus infections in holders of exotic squirrels in Germany.

Pathogens spread in certain parts of Europe

According to the current state of knowledge, the causal Bornavirus is regionally limited in parts of eastern and southern Germany, Austria, Switzerland and Liechtenstein, as the communication states.

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

"The unreported number of Bornavirus infections in fatal brain infections is unknown because the infection has so far not been considered in routine examinations."

Further research is now to clarify, among other things, how common Bornavirus infections actually are in humans, how the virus is diagnosed in good time and how the deadly course of 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 "hot head disease of horses", which is caused by the Bornasch disease virus, was first described in 1813.

The disease got its name in 1894 when an entire stable full of cavalry horses fell ill in the city of Borna (Saxony).

The field shrew is the natural reservoir of the Bornavirus.

It was previously known that the shrew's virus is excreted in the urine and saliva and is occasionally transmitted to other mammals - so-called false hosts of this virus - who can then develop Bornaschen's disease.

Horses and sheep are particularly affected. While infected shrews show no signs of disease, the virus affects the central nervous system in the wrong hosts and extensive brain damage occurs, probably due to the attack by the body's own immune cells.

A transmission of the virus from infected horses or sheep among each other or to other mammals has not yet been demonstrated. The virus is not eliminated by the wrong hosts and is hardly detectable in their blood.

Evidence of virus-specific antibodies clearly confirmed

After two patients with no known risk factors and despite intensive treatment at the Neurological Clinic of the University Hospital Erlangen had died of severe inflammation of the brain of unknown cause, the team of neuropathologists, neurologists, pathologists and virologists led by Prof. Ensser had their tissue samples taken using modern next-generation technology -Sequencing method examined.

To this end, the RNA sequences of millions of RNA molecules were determined and compared bioinformatically with sequence databases of known pathogens.

This enabled the scientists to identify large quantities of the genetic material of a virus in the brain of one of the deceased patients. The nucleic acid sequence of this virus was clearly assigned to the classic Borna disease virus 1 (BoDV-1).

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

Virus detected in donor organ recipients

Another group of researchers was able to detect the Bornavirus in three recipients of donor organs from a postmortem organ donor who is considered a virus carrier.

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

The cases examined do not confirm past published studies of widespread occurrence of BoDV-1 infections in humans and certain neuropsychiatric disorders.

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

According to the information, all patients and the organ donor came from one of the known distribution areas of BoDV-1.

Controversy over the dangerousness of the virus

There has been scientific controversy in the past about the virus and its dangerousness.

Research at the Robert Koch Institute (RKI) on possible Bornavirus infections in humans, which began in the early 1990s, was discontinued in 2005.

At the time, it was said that despite years of efforts, no reliable evidence of a risk to humans had been found.

Alleged Bornavirus evidence in human samples was later traced back to contamination in the laboratory.

The topic had also received a lot of attention because some of the scientists described the Bornavirus as a factor in the development of diseases such as depression and schizophrenia.

However, according to the Gesellschaft für Virologie (GfV), there is still no scientifically substantiated evidence for the thesis, which is sometimes published, that a large part of the population is infected with the virus and is related to the occurrence of various neurological and psychiatric disorders .

The GfV experts see a great need for further research into the virus in order to clarify open questions regarding the spread, transmission routes, early diagnosis and therapy of the virus. (ad)

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