Pancreas disease (PD) in sea‐reared Atlantic salmon, Salmo salar L., in Norway; a prospective, longitudinal study of disease development and agreement between diagnostic test results

Abstract

A prospective longitudinal study was performed on three cages at each of three Norwegian Atlantic salmon seawater sites that experienced outbreaks of pancreas disease (PD). Once salmonid alphavirus (SAV) ribonucleic acid (RNA) was detected by real-time RT-PCR (Rt RT-PCR) at a site, it became detected in all studied cages and was persistently found until the end of the study period up to 19 months after first detection. SAV-specific antibodies were detected at all sites until the end of the study period and were also found at a high prevalence in broodfish at the time of stripping. No evidence of increased viral activity was detected in these broodfish. One site tested negative over several months prior to the first detection of SAV by Rt RT-PCR and SAV-specific antibody, which occurred 1 month prior to clinical manifestations of PD. Moribund fish or thin fish/runts that were sampled after the first PD diagnosis had almost twice the risk of testing positive by one or more diagnostic tests compared to that of randomly selected apparently healthy individuals. This paper describes the first detailed investigation of the disease development of PD at site and cage level in Norway, as well as an assessment of the performance and agreement of the commonly used diagnostic tests.

First outbreak of sleeping disease in Switzerland: disease signs and virus characterization

“…Furthermore, 2 samples, each containing a pooled tissue homogenate from gill, heart, head kidney, brain and pyloric caeca from 5 fish obtained at the last sampling, were inoculated on Chinook salmon embryo (CHSE-214) cell monolayers for virus isolation and identification by an indirect immunofluorescence test (IFAT) according to the procedure described by Jansen et al (2010).…”

“…Graphic presentation of the phylogenetic tree was performed in MEGA5 Software (Tamura et al 2007). The nucleotide sequences obtained in this study were deposited in GenBank with accession numbers HG937642 and HG937643.Furthermore, 2 samples, each containing a pooled tissue homogenate from gill, heart, head kidney, brain and pyloric caeca from 5 fish obtained at the last sampling, were inoculated on Chinook salmon embryo (CHSE-214) cell monolayers for virus isolation and identification by an indirect immunofluorescence test (IFAT) according to the procedure described by Jansen et al (2010).A third batch of fingerlings, each at about 30 g, was introduced in October 2013 (Fig. 1).…”

Recommended reporting standards for test accuracy studies of infectious diseases of finfish, amphibians, molluscs and crustaceans: the STRADAS-aquatic checklist

“…For infectious diseases, sampling of clinically affected animals will typically yield higher estimates of diagnostic sensitivity for organism detection tests; hence, reporting of clinical status and longitudinal mortality data is important. Jansen et al (2010) provide detailed descriptions of disease progression at all 3 sites (including Site 2 as in the example) and present the longitudinal mortality and sampling data. Their Tables 2 & 3 clearly present dates of sampling, including sampling numbers (relative to time of disease diagnosis), results for the TUEs (including virus isolation), and the clinical status of tested fish.…”

“…Fig. 1 in Jansen et al (2010) is also a good example because it combines histopathological findings, pathogen load, serological status and clinical signs to describe the spectrum of disease stages in the study population. Caraguel et al (2009) provide a novel example of presentation of test results across multiple populations.…”

“…For instance, if a test was evaluated for screening purposes using a mixed population with apparently healthy and moribund fish, one could use the diagnostic sensitivity and specificity estimates of moribund fish only when testing to confirm clinically suspect (moribund) cases. Other study examples that provide covariatespecific estimates for various clinical categories include Jansen et al (2010) and, for separate agent genotypes, Gustafson et al (2008). (Caraguel et al 2009, p. 14).…”