A mortality event in wrasse species (Labridae) associated with the presence of viral haemorrhagic septicaemia virus

Abstract

Viral haemorrhagic septicaemia (VHS) is an infectious disease of farmed and wild fish and has an extensive host range in both freshwater and marine environments. In December 2012, a wrasse population consisting of ballan, Labrus bergylta (Ascanius), corkwing, Symphodus melops (L.), cuckoo, Labrus mixtus L., goldsinny, Ctenolabrus rupestris (L.), and rock cook, Centrolabrus exoletus (L.), held at a marine hatchery in the Shetland Isles, Scotland, experienced a mortality event. Approximately 10 000 wrasse were being held at the facility on behalf of an Atlantic salmon, Salmo salar L., aquaculture company prior to being deployed for the biological control of parasites on marine pen Atlantic salmon, aquaculture sites. Fish Health Inspectors from Marine Scotland Science initiated a diagnostic investigation, and subsequent diagnostic testing confirmed the site to be VHSV positive by qRT-PCR and virus isolation followed by ELISA. A VHSV genotype-specific qRT-PCR assay revealed that the isolates belonged to genotype III, the European marine strain of the virus. The virus genotype was further confirmed by nucleic acid sequencing of the partial nucleoprotein (N) and glycoprotein (G) genes followed by BLAST nucleotide searches. This study reports for the first time the detection of VHSV within multiple wrasse species and highlights the need for a comprehensive risk-based approach to the use of wrasse and other finfish species as biological controls within the aquaculture industry.

Cleaner fishes and shrimp diversity and a re‐evaluation of cleaning symbioses

“…The main limitations to using cleaner fishes have been adequate supply, their ability to escape and the influence of environmental conditions on cleaning activity and ectoparasite growth rates (Costello, ). Recent concerns suggest that wrasse species used as cleaners in Europe may also be the reservoirs of diseases in Atlantic salmon culture, for example viral haemorrhagic septicaemia (Munro et al ., ; Wallace et al ., ), amoebic gill disease (Karlsbakk et al ., ) and Aeromonas salmonicida (Aeromonadaceae) (Treasurer, ), further supporting certification of disease‐free cultured cleaners.…”

Susceptibility of goldsinny wrasse, Ctenolabrus rupestris L. (Labridae), to viral haemorrhagic septicaemia virus (VHSV) genotype III: Experimental challenge and pathology

“…(Hall et al, 2013;Munro et al, 2015) and describes VHSV pathogenicity for the species in an environment free from other infective agents. Pathological changes observed in wrasse following the infection differed from what is described as VHS in rainbow trout.…”

“…Finally, it is important to put the experimental results described in this report into a context with the observations made during the Shetland Islands VHSV infection . It could be argued that the proportion of moribunds observed in the bathimmersion challenges represent an upper limit to the mortality associated with the VHSV strain isolated from the Shetland occurrence (Hall et al, 2013;Munro et al, 2015), and that excess mortalities that may have occurred in that event were associated with other factors. Unfortunately, this upper limit cannot be regarded as definitive because the Shetland event likely differed to that described in this report with regard to VHSV dose and susceptibility of different wrasse stocks.…”

“…Under aquaculture conditions, VHSV gIII was found causing disease in turbot (Scophthalmus maximus) (Ross et al, 1994) and in rainbow trout (Oncorhynchus mykiss) (Dale et al, 2009;Duesund et al, 2010). In wrasse, infection with VHSV gIII was reported in 2012 (Hall et al, 2013;Munro et al, 2015), however due to the complex and mixed infection present in these wrasse, the Table 2 Scoring criteria developed to quantify histopathological changes observed in the heart atrium of goldsinny wrasse experimentally infected with VHSV 12-654 by virus immersion.…”

Outbreak of viral haemorrhagic septicaemia (VHS) in lumpfish (Cyclopterus lumpus) in Iceland caused by VHS virus genotype IV

“…Viral haemorrhagic septicaemia virus (VHSV) genotype III recently caused an epidemic in wrasse used as cleaner fish in net pens in Scottish waters (Hall et al., ). The finding of VHSV genotype IV in Lumpfish in Iceland and VHS genotype III in wrasse on the Shetland Isles north of Scotland in 2012 (Munro et al., ) highlight how cleaner fish captured from the wild may harbour relevant pathogens for farmed stocks. The findings reported here and the ones described by Munro and colleagues (Munro et al., ) underline the need for targeted surveillance (Murray, ) and warrant an extension of the list of susceptible species for VHSV in European legislation and in the OIE aquatic code.…”