Viral haemorrhagic septicaemia virus in marine fish and its implications for fish farming – a review

Abstract

Viral haemorrhagic septicaemia virus (VHSV) has, in recent decades, been isolated from an increasing number of free-living marine fish species. So far, it has been isolated from at least 48 fish species from the northern hemisphere, including North America, Asia and Europe, and fifteen different species including herring, sprat, cod, Norway pout and flatfish from northern European waters. The high number of VHSV isolations from the Baltic Sea, Kattegat, Skagerrak, the North Sea and waters around Scotland indicate that the virus is endemic in these waters. The VHSV isolates originating from wild marine fish show no to low pathogenicity to rainbow trout and Atlantic salmon, although several are pathogenic for turbot. Marine VHSV isolates are so far serologically indistinguishable from freshwater isolates. Genotyping based on VHSV G- and N-genes reveals four groups indicating the geographical origin of the isolates, with one group representing traditional European freshwater isolates and isolates of north European marine origin, a second group of marine isolates from the Baltic Sea, a third group of isolates from the North Sea, and a group representing North American isolates. Examples of possible transfer of virus from free-living marine fish to farmed fish are discussed, as are measures to prevent introduction of VHSV from the marine environment to aquaculture.

Relationship of farm salmon, sea lice, and wild salmon populations

“…For example, in 2001, sick juvenile pink salmon frequently had "bleeding at the base of the fins" (4), but this lesion does not occur in pink salmon exposed to Pacific-source L. salmonis under controlled laboratory conditions (20,32). Instead, reddening of the fins is commonly associated with stressful environmental conditions or bacterial and viral infections (35,36); however, none of these differentials were investigated in 2001, and their potential role in fish mortality that year remains unknown. Adding medical analysis to multidisciplinary investigations of fish population decline can increase our understanding of the cause and help government agencies develop cost-effective regulations to sustain healthy wild salmon populations.…”

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“…VHSV is temperature sensitive, and the related diseases occur at temperature changes below 15°C (Olesen, 1998, Skall et al, 2005. Surface water temperature of Black Sea changing between 28.06±0.90°C (in August) and 8.80°C±1.15°C (in February-March) (Aksungur et al, 2007).…”

A survey of viral haemorrhagic septicaemia virus in cultured sea bass and its virulence on juveniles of sea bass, Dicentrarchus labrax (Actinopterygii: Perciformes: Moronidae) and gilthead sea bream, Sparus aurata (Sparidae)

“…More than 80 species of fish living in freshwater, seawater, and brackish water around the world were found to carry VHSV (Anonymous 2012). Many cases of severe VHS in wild and cultured fish were reported in North America and Europe (Wolf 1988, Meyers et al 1999, Nishizawa et al 2002, while most isolates were obtained from asymptomatic carrier fish (Skall et al 2005).…”

“…Isolates obtained from fish from the Black Sea belong to the subgroup Ie (Nishizawa et al 2006, Altuntaş andOgut 2010). VHSV genotypes II and III are found in wild marine fish in the Baltic Sea, the North Sea, and Skagerrak (Skall et al 2005). VHSV-IV isolates, restricted to North America and Asia, have been collected from both freshwater and marine fish (Lumsden et al 2007).…”