VHS in wild living fish and experimental trasnmission of the virus

This study demonstrates that pike, brown trout and whitefish in wild waters revealed to a high degree antibodies against the viral haemorrhagic septicaemia virus (VHSV). Interactions between feral fish and fish in aquaculture were examined. Viral haemorrhagic septicaemia (VHS) outbreaks in pike occurred in 23 out of 45 brood stock. The temperature optimum for a VHS outbreak in pike (13–15°C) was much higher than for rainbow trout. In very small pike fry (less than 20 mm) hydrocephalus was the main symptom of the disease. VHS in brown trout was usually not apparent. In a water course in an endemic region, the epidemic develops independently within distinct populations. Fluctuations in the prevalence of antibodies in several distinct populations of brown trout during 4 years of observation argue for the maintenance of the epidemic within these populations. The experimental transmission of VHSV from rainbow trout to pike and from pike to rainbow trout, as well as from brown trout to rainbow trout was demonstrated.