No evidence for European bats serving as reservoir for Borna disease virus 1 or other known mammalian orthobornaviruses

Abstract

Background: The majority of emerging infectious diseases are zoonotic in nature and originate from wildlife reservoirs. Borna disease, caused by Borna disease virus 1 (BoDV-1), is an infectious disease affecting mammals, but recently it has also been shown to cause fatal encephalitis in humans. The endemic character of Borna disease points towards a nature-bound reservoir, with only one shrew species identified as reservoir host to date. Bats have been identified as reservoirs of a variety of zoonotic infectious agents. Endogenous borna-like elements in the genome of certain bat species additionally point towards co-evolution of bats with bornaviruses and therefore raise the question whether bats could serve as a potential reservoir of orthobornaviruses. Methods: Frozen brain samples (n = 257) of bats of seven different genera from Germany were investigated by orthobornaviral RT-PCR. Additionally, tissue slides of formalin-fixed paraffin-embedded material of a subset of these bats (n = 140) were investigated for orthobornaviral phosphoprotein by immunohistochemistry. Results: The brain samples were tested by RT-PCR without any evidence of orthobornavirus specific amplicons. Immunohistochemistry revealed a faint immunoreaction in 3/140 bats but with an untypical staining pattern for viral antigen. Conclusions: RT-PCR-screening showed no evidence for orthobornaviral RNA in the investigated bats. However, immunohistochemistry results should be investigated further to elucidate whether the reaction might be associated with expressed endogenous bornaviral elements or other so far unknown bornaviruses.

Update on Potentially Zoonotic Viruses of European Bats

“…On the other hand, CoV are very abundant in bats and have a high tenacity, making them more likely to be detected compared to e.g., Paramyxoviruses. Moreover, the lack of data on negative tested bats raises difficulties to draw conclusions [ 13 , 14 , 15 , 16 , 17 ]. Another factor is the availability of bat species for examination.…”

Borna Disease Virus 1 (BoDV-1): Aktueller Stand und Perspektiven

“…Feldspitzmäuse können offensichtlich persistent und asymptomatisch infiziert werden und das Virus auf der Haut, im Urin sowie in Speichel, Tränenflüssigkeit und Kot ausscheiden [25]. Im Gegensatz dazu wurde in einer Studie mit 257 Fledermäusen keine Infektion nachgewiesen [26]. Die BoDV-1-Sequenzen von Spitzmäusen und Fehlwirten clustern regional, was am Ehesten für eine Übertragung des Virus von Spitzmäusen, möglicherweise über ihre Ausscheidungen, auf die Fehlwirte ("Spill-over") spricht [16].…”