Abstract
Recently, the zoonotic capacity of the newly discovered variegated squirrel bornavirus 1 (VSBV-1) was confirmed in humans with a lethal encephalitis. Transmission to humans occurred by variegated and Prevost’s squirrels as presumed reservoir hosts but possible ways of virus shedding and the route of infection still need to be elucidated. Thus, the tissue distribution of VSBV-1 antigen and RNA was investigated in detail via immunohistochemistry (IHC) in six variegated and eight Prevost’s squirrels and by in situ hybridisation (ISH) in one Prevost’s squirrel, respectively. VSBV-1 antigen and RNA positive cells were most numerous in the nervous system and were also found in nearly all tissues and different cell types indicating a broad organ and cell tropism of VSBV-1. Presence of VSBV-1 in several organs might indicate potential virus shedding via various routes and implies the risk of intra- and interspecies transmission, respectively.
Highlights
New zoonotic infections are most commonly emerging from RNA viruses, about half of them cause neurologic diseases and about 80% are zoonotic[1,2]
In 2015, the novel zoonotic variegated squirrel bornavirus 1 (VSBV-1; species Mammalian 2 orthobornavirus, family Bornaviridae3) was detected in three variegated squirrel breeders suffering from a fatal meningoencephalitis and in one contact squirrel (Sciurus variegatoides)[12]
In the naturally infected squirrels virus VSBV-1 RNA was detected in many organs with highest viral RNA loads in the central nervous system (CNS), heart, lung, kidney, oropharyngeal swabs, skin and the urinary bladder[12,14,15]
Summary
New zoonotic infections are most commonly emerging from RNA viruses, about half of them cause neurologic diseases and about 80% are zoonotic[1,2]. In the naturally infected squirrels virus VSBV-1 RNA was detected in many organs with highest viral RNA loads in the central nervous system (CNS), heart, lung, kidney, oropharyngeal swabs, skin and the urinary bladder[12,14,15] This likewise dissemination of virus genome in species of the Callosciurinae and Sciurinae subfamily might identify these species as reservoir hosts capable of shedding infectious virus via several. Similarities in virus tissue distribution and clinical outcome in BoDV-1-infection and VSBV-1-infection in the different (possible) reservoir and accidental host species, respectively, enhance the need for a detailed morphological characterization of VSBV-1-antigen and RNA distribution in the different host systems This allows to illuminate potential ways of virus shedding by secretions and excretions as prerequisite for an evidence-based assessment of the risk for VSBV-1 transmission to humans and other animal species
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