Report E: DFO Fish Health Audit and Surveillance Summary by facility
This annual summary provides fish health data submitted by industry and collected by DFO in a table capturing all licensed marine aquaculture facilities culturing salmon in B.C. The left portion of the table presents the findings from the DFO Audit and Surveillance program, and the right portion, information from industry reported as per Conditions of Licence.
DFO surveillance audit activity includes the number of fish health audits, the number of sea lice audits, and the number of Condition of Licence inspections within a calendar year.
Results of polymerase chain reaction (PCR) screening are provided, as well as a list of the bacterial pathogens isolated, and whether a pathogen or disease has been confirmed by histopathological testing (microscopic examination). DFO veterinarians provide a diagnosis based on these findings.
The table summarizes industry-reported data including the number of times antibiotics and anti-louse treatments were used. Incidents where more than three motile sea lice were detected during the period between March 1 and June 30 are also reported, as DFO considers this a reportable “fish health event”.
Industry reports the number and nature of diagnosed mortality events as well as other mortality events not otherwise captured, such as culls (for management purposes) or non-bacterial events such as IHN. The treatment applied to the identified health event is also described.
Descriptions of diagnoses, diseases and pathogens identified in this report are available below. DFO veterinary staff and contract veterinary pathologists make farm-level and fish-level diagnoses, based on pathogen screening, bacterial culture and histopathology assessment of tissue samples. This list only reflects those which are identified in Report E and will be updated as necessary.
Site-specific data is only published once the facility has completed its production cycle.
When considering fish health data, it is important to keep the following definitions in mind:
“Disease”: an abnormality of form or function and can be caused by a suite of infectious, non-infectious and inherent factors
“Clinical Disease”: a stage of disease that reflects anatomic or physiologic changes that may produce recognizable signs and symptoms of a disease
“Endemic”: a disease that is characteristic of a certain location or population and is naturally present in the ecosystem
“Infectious disease”: a disease caused by the invasion and growth of a microorganism in or on a fish that affects the form or function of that fish
“Infectious outbreak’’: an occurrence of disease in a population as determined by the attending veterinarian with the indicating morbidity or mortality rate substantially higher than its normal level
“Pathogen”: microorganism causing damage (pathology) in or on a fish. This includes parasites, bacteria, rickettsia and viruses many of which are common and naturally present in the ecosystem. The presence of a pathogen does not mean the presence of disease
Federally-reportable pathogens are indicated with an asterisk. These are federally and internationally recognized diseases and pathogens that may have the potential to have a severe impact on fisheries and affect regional and national trade so they warrant urgent notification and immediate attention.
Bacterial Kidney Disease (BKD): BKD is a chronic disease of trout and salmon. Intensive testing of the female broodstock aims to prevent introduction of the bacterium that can lead to disease. Eggs from a female that show evidence of infection are considered potentially infected and discarded. Smolts raised in freshwater free of the bacterium may be exposed once in seawater. The causative bacterium, Renibacterium salmoninarum, is commonly found in wild salmonids and is shed in the feces of ill fish. The disease can be managed with antimicrobial agents.
Enteric Redmouth (ERM): ERM is a freshwater disease of trout and salmon that is self-limiting; i.e. resolves, in the marine environment. The disease has been diagnosed in many salmonid species in hatcheries, lakes and rivers in B.C., which can all serve as a reservoir for the bacterium Yersinia ruckeri. However, ERM can be avoided by good husbandry despite the presence of the pathogen. Disease, if it occurs, is most often managed without the use of antibiotics.
Furunculosis: Furunculosis is an endemic disease, principally of trout and salmon, that once severely limited aquaculture production and expansion. Outbreaks are now uncommon thanks to vaccine development and advancement in hatchery water supply disinfection technologies. The disease has been diagnosed in salmonids and non-salmonid species in hatcheries, lakes, rivers and coastal marine environments in B.C. which can all serve as a reservoir for the bacterium Aeromonas salmonicida. For those hatchery facilities where water supplies come from sources with diseased wild fish, and the marine sites near rivers carrying wild fish with disease, there is a risk that hatchery fish will be exposed to the pathogen prior to vaccination and a risk that fish at marine sites will be exposed when environmental stressors increase their vulnerability, resulting in the need for antimicrobial treatment.
*Infectious Haematopoietic Necrosis (IHN): IHN is an endemic disease of sockeye salmon that once posed a significant threat to the Atlantic salmon aquaculture industry in B.C. Outbreaks are now uncommon as a result of vaccine development. DFO monitors for the virus on sockeye salmon spawning grounds as sockeye smolts that survive outbreaks can transmit the virus into the marine environment. This reportable disease is untreatable and can be transmitted when infected fish are moved to an area where susceptible species exist.
*Infectious Pancreatic Necrosis (IPN): IPN is a viral disease that is not found on the coast of B.C. and can affect many non-salmonid species. DFO has maintained strict import measures to keep it out of the region. Results of the screening component of DFO’s Fish Health Program contribute to the confidence that coastal B.C. is free of the disease.
*Infectious Salmon Anaemia (ISA): ISA is a viral disease that is endemic in Eastern Canada but not found in B.C. The susceptible species are Atlantic salmon and brown trout. The screening component of DFO’s Fish Health Program, in addition to CFIA’s disease surveillance efforts, contributes to the confidence that B.C. is free of this federally reportable disease.
Loma salmonae: This parasitic disease of Pacific salmon can cause respiratory distress and render fish susceptible to other infections. Fish exposed to the infectious form of the parasite may develop diseased gills and reactions in the internal organs. Mortality as a result of this disease is highest when water temperatures are between 12°C to 17°C.
Mouth Rot (Myxobacteriosis): Mouth rot (also known as Ulcerative stomatitis) is ulceration with inflammation of the mouth. It is a disease found in cultured Atlantic salmon smolts, usually developing soon after entry into seawater. It is believed to be caused by the bacterium Tenacibaculum maritimum, but it appears that this alone is not sufficient to cause disease. T. maritimum is implicated in association with diseases of external surfaces of many cultured fish around the world and the disease found in B.C. is also found in Norway. The most characteristic sign is yellow patches on gums, palate, or gill rakers and occurs most commonly when seawater entry is to areas of high salinity. Treatment for this environmental disease accounts for most of the antimicrobial agents used in B.C.
Net Pen Liver Disease (NPLD): NPLD is a debilitating liver condition of farmed Atlantic salmon that is thought to be associated with a naturally-occurring blue-green algal toxin microcystin. This non-infectious disease is believed to be caused by salmon feeding on wild organisms that feed on blue-green algae. Affected fish have shrunken, yellow livers and the disease can be fatal, depending upon the extent of liver damage.
No significant disease present at the population level: This farm-level diagnosis is assigned by DFO veterinarians based on field observations, specific mortality rate, individual fish pathology reports, on-farm health records and pathogen identification tests.
Parasitic Meningitis and/or Encephalitis: Parasite infection of the brain or its lining results in inflammation, contributing to death. This condition is not considered to be infectious as there is no evidence of fish-to-fish transfer. Although numbers of affected fish in a population are assumed to be low, in instances of low background mortality, it can be the chief cause of death at a facility. In B.C. parasitic infections found in the brain (or brain lining) of Atlantic salmon include the following: 1. Microsporidia cerebralis; 2. a pre-sporogonic stage of an unidentified parasite of Class Myxosporea; and 3. Sphaerthecum destruens (also of Class Myxosporea).
Post-vaccination Peritonitis (PVP): PVP is inflammation within the abdomen, a side effect of vaccination. Fibrous bands can form between neighbouring organs, and between organs and the body wall, resulting in organ dysfunction contributing to death. The occurrence of PVP has decreased in frequency since 2008 when the Government of B.C., as the regulator of the aquaculture industry at the time, began formal tracking of the disease.
Rickettsiosis (PRSal): Rickettsiosis (also known as Salmonid Rickettsia Septicemia, SRS) is a chronic disease caused by the bacterium Piscirickettsia salmonis resulting in tissue inflammation throughout the body. This disease is of regional interest and is included in the surveillance screening because prior to 2005, it was found only in Atlantic salmon on the west coast of Vancouver Island. This disease is often self-resolving but outbreaks can be treated with antimicrobial agents.
Salmon Alphavirus (SAV): Salmon alphavirus is the causative agent of pancreas disease in farmed Atlantic salmon in Norway, Scotland and Ireland. DFO began screening for the pathogen in the Pacific region in 2013 in response to the emergence of the disease in cultured Atlantic salmon in Europe.
Winter Ulcer: Winter ulcer is a skin ulcer found in Atlantic salmon when temperatures are 8°C and below. The disease, confirmed with isolating the bacterium Moritella viscosa from the ulcer, is described in Atlantic salmon and other farmed fish in the North Atlantic but has not been found in other species in B.C. The disease tends to be found in younger fish and it is uncertain whether antibacterial treatments are effective. Affected fish often recover and related mortality is low.
*Viral Haemorrhagic Septicaemia, North American Strain, (VHS NAS): VHS is a viral disease caused by several strains of VHS virus. The marine type found in at least four marine fishes of the North Pacific (genotype IVa) has been detected in farmed Atlantic salmon but this virus is associated with low virulence, with no farm-to-farm spread. Pacific salmon are not affected and mortality in Atlantic salmon is very low. Disease, if any, resolves when temperatures rise above 12°C. This is a reportable disease because the freshwater forms of the virus are more virulent and can be transmitted when infected fish are moved to an area where susceptible species occur.
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