Classical Borna disease virus identified to cause severe encephalitis

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Investigations carried out by the Friedrich-Loeffler-Institut (FLI) in collaboration with a number of university hospitals identified the „classical“ Borna virus (Borna disease virus 1, BoDV-1; species Mammalian 1 Bornavirus) for the first time as likely source of severe inflammation of the meningis (encephalitis) in humans. The diseases occurred in three organ recipients from a single donor, two of them died hereinafter. One additional case exists, but it is not linked to the organ transplantation. Other pathogens that are known to cause encephalitis were not detected in any of the patients. At present, the involved institutions and the Robert Koch-Institute unanimously consider the BoDV-1-cases related to the organ recipients as a very rare event. 

The „classical“ Borna virus is a pathogen that has been known since the 19th century to cause Borna disease in animals, a rare, chronic and progressive inflammation of the meninges (meningoencephalitis). The disease mainly occurs in the horses and the sheep and is often fatal. The bicoloured white-toothed shrew is considered to be a natural reservoir for BoDV-1. 

BoDV-1 as a source of psychiatric diseases in humans was the subject of controversial discussions in the 1990s. However, this assumption has not been validated scientifically. The new results of the laboratory investigations confirmed now for the first time the evidence for human disease caused by BoDV-1 (acute encephalitis). BoDV-1 is distinct from the variegated squirrel borna virus 1 (VSBV-1, species Mammalian 2 Bornavirus), the virus that, in 2015, was found to cause encephalitis in the breeders of exotic squirrels.  

Investigations regarding the routes of transmission of BoDV-1 are in preparation, e. g.  In the context of the joint research project “ZooBoCo”, a project coordinated by the FLI and financed by the Federal Ministry of Education and Research. 

Very rare cases of human encephalitis caused by different viruses (e. g. human herpes virus 6, West-Nile-virus, Epstein-Barr virus, measles virus) after organ transplantation were reported in the scientific literature. In the future, BoDV-1 should be included in the list of pathogens considered in the differential diagnosis of causes of human encephalitis.

In summary, in the case of unclear human encephalitis, BoDV-1 should also be diagnostically clarified based on the latest study results.

Foto: Probenuntersuchung im FLI (© FLI)

(© FLI)