Emerging Pathogens

Salmon Pancreas Disease Virus (SPDv)

Salmon pancreas disease virus (SPDv) is the aetiological agent of pancreas disease (PD) in Atlantic salmon, Salmo salar L.  SPDv is an alphavirus that belongs to the Togaviridae family of viruses. Other members of the alphavirus group cause disease in terrestrial animals. PD in Atlantic salmon, resulting from an infection by SPDv, is one of the multiple forms of the disease that affects the pancreatic tissue. In addition to SPDv, there are a number of pancreas-related disease conditions of salmon that can be the result of infectious and non-infectious causes. However, the PD that affects European Atlantic salmon in Norway and the UK is mostly associated with SPDv infection.  SPDv occurs mainly in Atlantic salmon in their first or second year at sea. Infected salmon are often lethargic, with abnormal swimming behaviour, a poor feeding response, and an intolerance to exercise. Other changes frequently seen include a loss in body condition and internally, small red spots on the surfaces of internal organs (areas of haemorrhage), and a loss of fat reserves around the caeca. Microscopic lesions associated with PD include damage to the heart and skeletal muscle in addition to pancreatic damage.

Pancreas disease was first detected in farmed Atlantic salmon in Scotland in 1976 and then subsequently in Norway, France, and Spain. A disease showing microscopic lesions similar to SPDv was reported from the west coast of North America in 1987, however no virus was seen or isolated from this case and therefore no conclusions could be made as to whether SPDv was involved.  SPDv has not been reported in fish from North America.

Diagnostic tests including RT-qPCR assays exist, but have not been fully evaluated nor has their inclusivity been reviewed since the discovery of new SPDv genotypes (it is now recognized that SPDv isolates from different case reports from Europe show subtle differences in their genetic make-up; these difference genetic groups are referred to as genotypes). There are currently at least 6 different SPDv genotypes recognized that are associated with geographic or species preferences. The geographic origin of fish can potentially influence their susceptibility to SPDv infection and development of disease. The infectious potential of SPDv will vary between genotypes.

NAAHLS Research on Salmon Pancreas Disease Virus

An initial evaluation of the potential of SPDv to affect various Atlantic salmon strains commonly, such as the St. John River strain commonly cultured in salmon farms, is being coordinated by Nellie Gagné at the Gulf Fisheries Centre – Aquatic Animal Health Laboratory (GFC-AAHL) and Dr. Phil Byrne at DFO’s Gulf Biocontainment Unit – Aquatic Animal Health Laboratory (GBU-AAHL).  SPDv challenge trials involving Atlantic salmon are taking place within the high level biocontainment facilities of GBU-AAHL using SPDv genotypes imported from a Norwegian Laboratory. Although this work is still in progress, tissues collected from experimentally infected salmon have been transferred to GFC-AAHL where Nellie Gagné is currently evaluating the samples for SPDv and determining the effectiveness of various assay protocols. Dr. Byrne is reviewing the clinical and microscopic pathology from the same fish. This work will contribute towards enabling the National Aquatic Animal Health Program to have validated test assays prepared and to be vigilant for any possible appearance of PD or SPDv infection in fish from Canada or in fish being imported into Canada.

Link to OIE http://www.oie.int/doc/ged/d10038.pdf

Oyster Herpes Virus (OHv)

Oyster Herpes virus or Ostreid Herpes 1 virus is a viral infection that affects mainly Pacific oysters (Crassostrea gigas), but can also affect other bivalve species. It is found in Australia, China, Korea, Japan, Morocco, New Zealand, the US, and several countries in Europe. Although, Oyster Herpes virus is not listed as a regulated disease by the Canadian Food Inspection Agency (CFIA), this pathogen has been added to the list of pathogens that are being tested for as part of CFIA shellfish surveillance program in British Columbia.

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