Human Borna disease virus 1 (BoDV-1) encephalitis cases in the north and east of Germany

ABSTRACT

In 2021, three encephalitis cases due to the Borna disease virus 1 (BoDV-1) were diagnosed in the north and east of Germany. The patients were from the states of Thuringia, Saxony-Anhalt, and Lower Saxony. All were residents of known endemic areas for animal Borna disease but without prior diagnosed human cases. Except for one recently detected case in the state of Brandenburg, all >30 notified cases had occurred in, or were linked to, the southern state of Bavaria. Of the three detected cases described here, two infections were acute, while one infection was diagnosed retrospectively from archived brain autopsy tissue samples. One of the acute cases survived, but is permanently disabled. The cases were diagnosed by various techniques (serology, molecular assays, and immunohistology) following a validated testing scheme and adhering to a proposed case definition. Two cases were classified as confirmed BoDV-1 encephalitis, while one case was a probable infection with positive serology and typical brain magnetic resonance imaging, but without molecular confirmation. Of the three cases, one full virus genome sequence could be recovered. Our report highlights the need for awareness of a BoDV-1 etiology in cryptic encephalitis cases in all areas with known animal Borna disease endemicity in Europe, including virus-endemic regions in Austria, Liechtenstein, and Switzerland. BoDV-1 should be actively tested for in acute encephalitis cases with residence or rural exposure history in known Borna disease-endemic areas.

KEYWORDS:

• Borna disease
• Borna disease virus 1
• bornavirus
• surveillance
• epidemiology

Acknowledgements

The technical assistance of Alexander Schlaphof, Corinna Thomé-Bolduan and Agnieszka Malota for serology is greatly acknowledged, as well as the help of Birgit Muntau, Alexandra Bialonski and Heike Baum for molecular assays and sequencing, and Petra Allartz and Petra Eggert (all Hamburg) for immunohistology and in situ-hybridization.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This study was performed within ZooBoCo (Zoonotic Bornavirus Consortium) and funded by the German Bundesministerium für Bildung und Forschung (BMBF) [grant numbers 01KI2005C and F to DT and HW].