A new bunya-like virus associated with mass mortality of white-clawed crayfish in the wild

We report the discovery of a new enveloped, spherical virus belonging to the Phenuiviridae family of negative ssRNA viruses associated with a massive outbreak in a French population of the endangered white-clawed crayfish Austropotamobius pallipes. We call this virus Bunya-like Brown Spot Virus (BBSV) and characterize it using transmission electronic microscopy, genome sequencing and clinical signs. Infected specimens show discolored brown spots on the cuticle. Using RNA-seq data we assembled a partial sequence for the L, M and S genome segments of BBSV. Phylogenetic analyses using all three segments show this virus is closely related to the Wenling crustacean virus 7 (China) and to a bunya-like virus found in feces of the European otter. Our survey of the mass mortality event indicates the virus is less virulent than the crayfish plague caused by Aphanomyces astaci. Overall, the discovery of BBSV provides a new important asset to monitor A. pallipes populations.