Studies on resistance to infectious pancreatic necrosis virus in Atlantic salmon (Salmo salar)

• Main Author: Plant, Karen Patricia
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: University of Stirling 2000
• Subjects: Atlantic salmon; Fishes Diseases; Norway; Salmo salar
• Online Access: http://hdl.handle.net/1893/30835; http://dspace.stir.ac.uk/bitstream/1893/30835/1/13916336.pdf

Infectious pancreatic necrosis virus (IPNV) is responsible for serious mortalities in postsmolt Atlantic salmon (Salmo salar) annually in both Scotland and Norway. The huge financial losses involved and the lack of control measures have prompted attempts to produce IPN vaccines and disease resistant strains of fish. A characteristic of IPNV is its ability to persist in a latent carrier state and to ensure stocks of fish are truly virus free there is a need for highly sensitive diagnostic methods. In this study microsatellites were employed to assign fish susceptible to IPN in the field to families. Laboratory challenges were performed on 24 families and various humoral immune parameters were measured. A variety of diagnostic techniques were also developed, their sensitivity and specificity evaluated and compared to tissue culture. Parental Atlantic salmon and offspring susceptible to IPN in the field were genotyped using a published multiplex microsatellite PCR adapted for use with fluorescent genotyping systems. The reliability and utility of the genotyping system was evaluated with positive results. The majority of susceptible fish could not be assigned to parents since the fish were found to be from a mixed stock. Various experimental challenges with IPNV infected tissue homogenate were performed on post-smolts, however they did not produce mortality or induce clinical IPN. As a result of this virus titre was used as an indirect measurement of disease resistance. Atlantic salmon post-smolts were found to effectively clear cell cultured IPNV, isolate Br from Shetland. A second Shetland isolate (Os) was found to actively replicate in the fish while isolate Br was rapidly cleared. To increase virulence isolate Os was passaged once further through fish prior to use in challenging 24 families of PIT 0 8 tagged Atlantic salmon. At week 3 mean viral titres for each family ranged from 10 to 1011 TCID5o/g kidney. Using these data six families were targeted to follow through to week 7, two with low titres, two with ...