Ph.D. study by Helle Frank Skall (Danish Veterinary Laboratory)
Supervisors: Jens Laurits Larsen (The Royal Veterinary and Agricultural University) and Niels Jørgen Olesen (Danish Veterinary Laboratory)
Normal intensive husbandry with animals is usually performed in closed systems where the interaction between farmed and wild animals can be reduced and introduction of disease can be minimised by measures such as control of access and proper fencing. In the case of fish farming the situation is very different. In most cases fish are raised in direct contact with the same water, as free living fish inhabits. Transfer of pathogens is eased by water compared to air.
Regular outbreaks of viral haemorrhagic septicaemia (VHS) and infectious pancreatic necrosis (IPN) in fish farms are suspected to be caused by infected free living marine or freshwater fish species.
The recent findings of a large reservoir of VHS virus and Birnavirus serogroup II (an IPN-like virus) in marine fish have enforced the need for studies on the possible interactions between free living and farmed fish. Recent severe outbreaks of VHS in year 2000 in Denmark are thus suspected to be due to transfer of the virus by up stream migrating rainbow trout (Oncorhynchus mykiss) or white fish (Coregonus sp.).
The overall aim of the proposal will be to examine whether transfer of diseases between farmed and free living fish do take place.
The project will elucidate the importance for aquaculture of the frequent findings of the 2 viruses, viral haemorrhagic septicaemia virus and birnavirus serogroup II, in wild fish.
The objectives of the project are to characterise VHSV collected from farmed and free living fish, to develop and assess new typing methods for VHSV, perform scientific cruises to elucidate the epidemiology of fish viruses in the marine environment, with respect to seasonality, organ tropism and pathogenicity for marine fish, and to determine the pathogenicity of VHSV isolates from farmed and free living fish by infection trials in rainbow trout.