Spread of epizootic haematopoietic necrosis virus (EHNV) in redfin perch (Perca fluviatilis) in southern Australia

Distribution and Host Range of Ranaviruses

“…While few fi sh become infected, the mortality rate of infected individuals appears to be high (Whittington et al 1994(Whittington et al , 1999. In contrast, EHNV causes severe disease in redfi n perch, affecting high proportions of populations of fi ngerlings and juveniles in endemic areas, and also naïve adults that enter new areas (Langdon et al 1986b ;Langdon and Humphrey 1987 ;Whittington et al 1996 ). Anecdotal evidence suggests that redfi n perch populations exposed to EHNV can recover over a few years.…”

“…A survey to detect viral infections of salmonids conducted in Australia between 1981 and 1984 did not identify any viruses (Langdon et al 1986a ), so EHNV may not have been present in trout prior to these fi rst mortality events. Although redfi n perch populations were not surveyed, there was no record of prior mass mortality (Whittington et al 1996 ). To date, there have been no other known cases of EHNV mortality in the wild other than redfi n perch, despite the fact that at least 14 additional species are known to be susceptible to this ranavirus according to experimental challenges (Whittington et al 2010 ;Becker et al 2013 ).…”

“…In redfi n perch, there has been progressive spread of EHNV into river systems, possibly due to natural fi sh migration, fi sh releases, and avifauna (Whittington et al 1996 ). Waterborne infection and ingestion of infected fi sh are transmission routes of EHNV between susceptible hosts within a population, but longer distance spread is likely a result of human activity, particularly by movement of infected trout fi ngerlings in aquaculture (Langdon et al 1988 ;Whittington et al 1994Whittington et al , 1999.…”

Further observations on the epidemiology and spread of epizootic haematopoietic necrosis virus (EHNV) in farmed rainbow trout Oncorhynchus mykiss in southeastern Australia and a recommended sampling strategy for surveillance

“…As the virus is believed to be pathogenic for a wide range of fish species, including several that are rare or endangered (Langdon 1989), further spread of EHNV through movements of farmed salmonids is undesirable. For this reason, farms in the known-infected catchments are subject to restrictions that preclude movement of live fish to putatively uninfected catchments (Whittington & Hyatt 1996). Field surveys are planned to accurately map the distribution of EHNV in catchments in New South Wales.…”

Viruses of Freshwater Finfish in the Asian–Pacific Region

“…Further, ulcerative dermatitis, swim bladder oedema and necrosis have been described in EHNVinfected rainbow trout [49]. EHNV is extremely resistant to drying, surviving for months in water, and persisting in frozen fish tissues and carcasses for at least a year [36,58]. There is no vaccine available for the control of EHN and hence, bio-security, routine surveillance and good husbandry practices that reduce physiological stressors play vital role in preventing this disease.…”