Sprivivirus Genome sequencing and assembly. Sprivivirus

A severe field outbreak of a rhabdoviral disease, occurred in 2016 in black bullhead catfish farmed in Italy, is fully described. Diseased fish showed signs of central nervous system infection as well emaciations and hemorrhagic petechiae on the skin at the fin bases, abdomen and gills. A cytopathogenic effect was observed in cell culture and confirmed by electron microscopy, immunofluorescence and generic primers targeting the N gene of fish rhabdoviruses. All laboratory analysis confirmed the unique aetiological agent of the disease observed and the viral isolate was tentatively called Icatalurid Rhabdovirus (IcRV). By deep sequencing of viral isolate the full viral genome was assembled and specific primers targeting the whole glycoprotein G were designed. The complete G protein of the 2016 virus, together with 14 viral strains stored in our repository and detected in diseased catfish in the years 1993-2016, were phylogenetically analyzed and genetic distances among Italian IcRV strains were also estimated. Our results show that all the IcRV strains belong to the genus Spirivirus and are closely related to the tench rhabdovirus (TenchRV).The field outbreak was followed over a six months period and surviving catfish developed specific antibodies response against the IcRV, detected by 50% plaque reduction assay. The outbreak ended with a total mortality of 90%.Italian catfish production is constantly decreasing, mainly due to viral infections, including the newly characterized IcRV. Data presented in this work will assist to investigate the molecular epidemiology and the diffusive dynamics of this virus and to develop adequate surveillance activities.