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Viral haemorrhagic septicaemia virus (VHSV) was isolated from mortalities occurring in populations of mummichog, Fundulus heteroclitus, stickleback, Gasterosteus aculeatus aculeatus, brown trout, Salmo trutta, and striped bass, Morone saxatilis, in New Brunswick and Nova Scotia, Canada. The isolated viral strains produced a cytopathic effect on the epithelioma papillosum cyprini cell line. Serum neutralization indicated the virus was VHSV and sequencing identified the rhabdovirus isolates as the North American strain of VHSV. Phylogenetic analysis indicated that the isolates are closely related and form a distinguishable subgroup of North American type VHSV. To our knowledge, this is the first report of VHSV in mummichog and striped bass. [ABSTRACT FROM AUTHOR]

Nodaviruses (NNV) are responsible for causing disease outbreaks mainly in hatchery-reared larvae and juveniles of a wide variety of fishes throughout the world. This disease has seriously limited the culture of marine fishes over the last decade. In the Atlantic provinces of Canada, disease caused by a nodavirus was first reported in juvenile Atlantic cod being reared in Nova Scotia, in 1999. More recently, disease outbreaks caused by nodavirus have been identified in hatchery-reared Atlantic cod and haddock in Newfoundland and New Brunswick, respectively, and along the east coast of the USA. The presence of NNV in wild Atlantic cod adults and wild winter flounder has also been reported. Nodaviruses were isolated from cultured Atlantic cod and haddock, as well as from wild winter flounder from a variety of geographical localities, and their virus coat (capsid) protein genes were partially sequenced. An analysis of the data indicates that all of the nodaviruses isolated from eastern North America were closely related to one another, but that they were distinct from the European isolates already sequenced. Regardless of host species, isolates from close geographical localities were more similar than those from distant geographical areas. At the protein level, differences in coat protein sequences were seen only for strains isolated from Atlantic cod originating from Newfoundland. Our results suggest that NNV may have been present in the Atlantic off Canada and on the east coast of the USA for some time, and has evolved to form a monophyletic group, distinct from other isolates found in cold-water species. Non-lethal methods for detection of NNV are necessary to develop management strategies for this disease, and would be an asset to diagnosticians and producers. Based on the results of this study, new primers were designed and developed for an improved RT-PCR assay able to detect North Atlantic nodaviruses in ovarian fluids, eggs and other tissues. The application of this test to field samples is discussed.

Piscine nodaviruses (Betanodaviridae) are frequently reported from a variety of cultured and wild finfishes. These non-enveloped, single-stranded RNA virions cause viral encephalopathy and retinopathy (VER), also known as viral nervous necrosis (VNN) or fish encephalitis. Recently, nodavirus infections have posed serious problems for larval and juvenile cultured halibut Hippoglossus hippoglossus in Norway and Scotland. To date, no such viruses have been described from any cultured or wild pleuronectid in Atlantic Canada. Obviously, there exists a need to survey wild populations of pleuronectids to assess the risk of potential transfer of nodavirus from wild to caged fishes. This paper presents the results of monthly surveys (April 2000 to March 2001) of viruses from wild winter flounder Pleuronectes americanus collected from Passamaquoddy Bay, New Brunswick, Canada. Tissue samples from wild flounder were screened initially on commercial cell lines (EPC, SSN-1, SHK and CHSE-214) for any evidence of cytopathic effect (CPE). After confirmation of CPE, nodavirus identification was achieved using reverse transcription polymerase chain reaction (RT-PCR) analysis. We detected nodavirus from only 1 out of 440 flounder (0.23%) examined. This is the first report of piscine nodavirus isolated from wild winter flounder in Atlantic Canada, and although this prevalence may seem low, we discuss the implications of this finding for Canada's emerging halibut aquaculture industry.