Isolation of a New Infectious Pancreatic Necrosis Virus (IPNV) Variant from Genetically Resistant Farmed Atlantic Salmon (Salmo salar) during 2021–2022

Abstract

Infectious pancreatic necrosis (IPN), caused by IPNV, affects several species of farmed fish, particularly Atlantic salmon, and is responsible for significant economic losses in salmon aquaculture globally. Despite the introduction of genetically resistant farmed Atlantic salmon and vaccination strategies in the Chilean salmon industry since 2019, the number of IPN outbreaks has been increasing in farmed Atlantic salmon in the freshwater phase. This study examined gross and histopathological lesions of IPNV-affected fish, as well as the IPNV nucleotide sequence encoding the VP2 protein in clinical cases. The mortality reached 0.4% per day, and the cumulative mortality was from 0.4 to 3.5%. IPNV was isolated in the CHSE-214 cell line and was confirmed by RT-PCR, and VP2 sequence analysis. The analyzed viruses belong to IPNV genotype 5 and have 11 mutations in their VP2 protein. This is the first report of IPN outbreaks in farmed Atlantic salmon genetically resistant to IPNV in Chile. Similar outbreaks were previously reported in Scotland and Norway during 2018 and 2019, respectively. This study highlights the importance of maintaining a comprehensive surveillance program in conjunction with the use of farmed Atlantic salmon genetically resistant to IPNV.

Evolution of an Extended Pathogenicity Motif in VP2 of Infectious Pancreatic Necrosis Virus Isolates from Farmed Rainbow Trout in Turkey

“…A recent analysis of IPNV isolated from diseased, vaccinated, and resistant freshwater salmon in Chile described eight configurations at VP2 positions 217, 221, and 247, which, however, do not include the PTE motif. All of these isolates showed evidence of pathogenicity in gross pathology, histopathology, and cell culture [ 31 ]. Our analysis additionally identified two IPNV isolates from a turbot and a rainbow trout carrying yet another motif (PTT), which apparently is rare but points to the fact that IPNV infecting seawater and freshwater salmonids can adapt the hypervariable region in the VP2 subject to influences in various natural and farmed environments.…”

A guide to assess the use of gene editing in aquaculture

“…[52][53][54][55] Indications are that Atlantic salmon that were fixed using selective breeding for a major trait locus giving high resistance to the disease 56,57 are not as resistant to some variants of the virus. [58][59][60] The continuation of selective breeding for such traits might act as a backup and make it more challenging for the disease agent to overcome host resistance.…”

Unexpected delayed incursion of highly pathogenic avian influenza H5N1 (clade 2.3.4.4b) in the Antarctic region

“…Despite the perceived remoteness, low pathogenicity avian influenza viruses and antibodies against these viruses have previously been detected in various seabird species nesting at sites along the Antarctic Peninsula and South Shetland Islands, with viral genomes illustrating phylogenetic connectivity to viruses circulating on other continents 6,7 . As a result, the Scientific Committee on Antarctic Research (SCAR) Antarctic Wildlife Health Network (AWHN) had considered the risk of incursion of the recent panzootic HPAIV H5 into the Antarctic region in 2022/23 summer season to be high 8 , and considerably higher in 2023/24 following virus spread to the southernmost regions of South America 9 , infecting seabirds including Magellanic penguins (Spheniscus magellanicus) and Humbold penguins (Spheniscus humboldti), and several species of marine mammals (9).…”