Infectious pancreatic necrosis virus (IPNV) - Infectious pancreatic necrosis (IPN)

Introduction

The susceptibility to IPNV infection is highly dependent on the genetic characteristics of the test fish. Atlantic salmon are susceptible to IPN by experimental infection as first feeding fry (fresh water) and as post-smolts (sea water). A Norwegian IPNV strain originating from an outbreak in post-smolts is used for all challenges. The virus is a serotype Sp/N1, characterized as highly virulent and carrying putative molecular virulence marker motifs.

Cohabitation challenge of smolts (sea water)

Pre-smolts to be included in a bath or cohabitant challenge study are photoperiod-manipulated to smoltify. Challenges can be performed within 1-3 weeks after transfer to sea water. For cohabitant challenge studies, 20% i.p. injected shedders are introduced to the challenge tank. Fish are observed throughout a <35-day period.

Immersion challenge of fry (fresh water)

Fish of different genetic characteristics can be kept in separate tanks or mixed in one tank during challenge. Possible tank effects can be reduced by mixing all families in one tank. The fish (0.1-0.2 grams in average weight) will be challenged by immersion 1-3 weeks after onset of start feeding. Mortality is recorded for 35-50 days. Subpopulations of fish from the challenged fish pool are typically identified by DNA fingerprinting.

Challenge test in Atlantic salmon populations with high (HR) and low (LR) resistance to IPN.