Infectious Pancreatic Necrosis (IPN) is a highly contagious systemic birnavirus disease of young fish of Salmonid species held under intensive rearing conditions. The disease most characteristically occurs in rainbow trout (Oncorhynchus mykiss), brook trout (Salvelinus fontinalis), brown trout (Salmo trutta), Atlantic salmon (Salmo salar) and several Pacific salmon species (Oncorhynchus spp.).
It mostly occurs under intensive rearing conditions in Salmonids hatcheries or in Post-Smolt Atlantic salmon in sea-cages.
The IPN virus is a birnavirus. The original serotype isolated from rainbow trout fingerlings is called VR-299. Since then, several serotypes have been identified and, in 1995, two serogroups, A and B, were established, each containing serotypes with different geographic origins. The most frequently found and virulent serotype is the Sp serotype.
The lethality of the virus depends on the strain, the species and age of the fish. Predisposing stress-inducing factors, such as first feeding, high stocking density, fluctuations in water temperature, salinity and handling, are believed to favour the onset of clinical disease. Outbreaks can occur all year round, at water temperatures as low as 4 ° C and as high as 18 °C.
Infectious Pancreatic Necrosis virus is a bi-segmented double-stranded RNA virus of the family Birnaviridae. At least nine serotypes exist. Susceptibility decreases with increasing age, with complete resistance to clinical disease in fry/fingerlings being reached at about 1500 degree-days (value obtained by multiplying the age in days by the average temperature during the lifespan) except for Atlantic salmon Smolts, which develop the disease within weeks following transfer from freshwater to seawater (Merck - Infectious Pancreatic Necrosis Virus). |
