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.
Subject(s)
Fish Diseases/diagnosis , Fish Diseases/pathology , Pancreatic Diseases/veterinary , Salmo salar/virology , Alphavirus/physiology , Animals , Antibodies, Viral/blood , Fish Diseases/virology , Longitudinal Studies , Norway , Pancreatic Diseases/diagnosis , Pancreatic Diseases/pathology , Pancreatic Diseases/virology , Reproducibility of Results , Reverse Transcriptase Polymerase Chain Reaction/veterinarySubject(s)
Fish Diseases/microbiology , Fish Diseases/pathology , Francisella/isolation & purification , Gadus morhua/microbiology , Gram-Negative Bacterial Infections/veterinary , Granuloma/veterinary , Animals , Choroid/pathology , DNA Primers/chemistry , DNA, Bacterial/chemistry , Fisheries , Francisella/classification , Francisella/genetics , Francisella/pathogenicity , Gram-Negative Bacterial Infections/microbiology , Gram-Negative Bacterial Infections/pathology , Granuloma/microbiology , Granuloma/pathology , Liver/pathology , Molecular Sequence Data , RNA, Ribosomal, 16S/genetics , Sequence Homology , Spleen/pathologyABSTRACT
The aims of this study were to investigate the content of emamectin in blood, mucus and muscle following field administration of the recommended dose, and correlation with sea lice infection on the same fish (elimination study). The tissue distribution of tritiated emamectin benzoate after a single oral dose in Atlantic salmon was also investigated by means of whole-body autoradiography and scintillation counting (distribution study). In the elimination study, concentrations of emamectin benzoate reached maximum levels of 128, 105 and 68 ng/g (p.p.b.) for blood, mucus and muscle respectively, on day 7, the last day of administration. From day 7, the concentration in the blood declined until concentration was less than the limit of detection on day 77. The concentration was higher in mucus compared with plasma (P < 0.05) except on days 7 and 21. The concentration of emamectin benzoate decreased gradually from the end of treatment (day 7) to day 70 with half-lives of 9.2, 10.0 and 11.3 days in muscle, plasma and mucus respectively. The distribution study demonstrated a high quantity of radioactivity in mucous membranes (gastrointestinal tract, gills) throughout the observation period (56 days). Activity was high in the epiphysis, hypophysis and olfactory rosette throughout the study. The highest activity was observed in the bile, indicating this to be an important route for excretion. The distribution study confirmed the results from the elimination study with respect to concentrations in blood, skin mucous and muscle.
