Tracking Aquatic Animal Diseases: the Fisheries and Oceans Canada (DFO) Centre for Aquatic Animal Health Research and Diagnostics (CAAHRD)
Preventing the spread of aquatic animal diseases within Canada and guarding against the introduction of exotic pathogens from other countries is critical to safeguarding the health of Canada’s aquatic resources and our multi-billion dollar export market in fish and seafood products. In an ongoing effort to reduce the incidence of these diseases, Fisheries and Oceans Canada’s (DFO’s) Centre for Aquatic Animal Health Research and Diagnostics (CAAHRD) oversees a virtual network of scientists involved in a variety of research in support of the National Aquatic Animal Health Program (NAAHP).
The mandate of the National Aquatic Animal Health Program, a science-based regulatory program co-delivered by Fisheries and Oceans Canada and the Canadian Food Inspection Agency (CFIA), is to protect Canada’s aquatic resources by preventing the introduction or spread of infectious diseases in wild or farmed aquatic animals (finfish, molluscs and crustaceans).
“The Centre for Aquatic Animal Health Research and Diagnostics coordinates targeted research, the development of quality diagnostics and the provision of sound scientific advice in support of the National Aquatic Animal Health Program as well as regional aquatic animal health programs overseen by Fisheries and Oceans Canada,” says Dr. Peter Wright, Director of the Centre for Aquatic Animal Health Research and Diagnostics and National Manager of the National Aquatic Animal Health Laboratory System. “The goal is to keep exotic diseases out and to ensure that diseases confined to particular areas don’t spread through the movement of fish or fish products. In addition, Canada has to satisfy trading partners that its exports of fish and fish products do not carry any infectious diseases, and that rule of trade requires a lot of testing.”
While most aquatic animal diseases pose no risk to humans, meaning the affected species are safe to eat and handle, they can be economically devastating for aquaculture operations and wild fisheries, which is the primary concern of the National Aquatic Animal Health Program. There are about 42 aquatic animal diseases of concern — for which Canada has potential host species — that can have an economic impact on finfish, shellfish and crustacean fisheries. Some of these aquatic diseases are endemic throughout Canada, others occur only regionally, while others are exotic (foreign) to Canada.
A New Test for Infectious Salmon Anaemia Virus
One such disease is Infectious Salmon Anaemia Virus (ISAV), which can cause mass die-offs in Atlantic salmon populations. Common symptoms of this virus include inflammation of the liver and spleen, hemorrhaging, congestion of internal organs and anemia, often leading to death. “In the mid-1990s, Infectious Salmon Anaemia Virus devastated the Bay of Fundy causing die-offs of farmed Atlantic salmon,” says Dr. Wright.
At the Gulf Fisheries Centre in Moncton, New Brunswick, Fisheries and Oceans Canada molecular biologist Nellie Gagné recently developed a new test for Infectious Salmon Anaemia Virus that detects the presence or absence of a particular part of the pathogen’s genetic code in fish or fish samples. Over the past three years, Gagné has collaborated with the Atlantic Veterinary College to validate the effectiveness of the new virus test to ensure it is measuring what it’s intended to measure. Results of the validation research — which involved computer modelling and complex statistical analysis of how the test performed in comparison with other tests for Infectious Salmon Anaemia Virus — revealed that the new test is more sensitive than other tests for this pathogen making it ideal for screening populations.
Validating the Effectiveness of Diagnostic Tests
“A test needs to be sensitive, reliable, robust, repeatable and fit-for-purpose,” says Nellie Gagné. “Our tests are carefully optimized to meet these requirements, and these characteristics have been evaluated during validation research.” The Infectious Salmon Anaemia Virus test is included in a suite of diagnostic techniques used to track the disease in Atlantic salmon populations.
Developing quality diagnostic tests and validating their effectiveness for how the National Aquatic Animal Health Program intends to use them is critical considering the consequences of a false positive or false negativeFootnote 1 to the industry. “If someone wants to move fish from one area to another, you need to ensure there are no false negative tests for a disease or you would be moving animals that are actually infected,” says Dr. Wright. “At the same time, having a false positive could potentially have a huge impact on the export of a particular fish or fish product because some countries will completely ban any imports of certain species if a particular disease is present in the exporting country. Nellie Gagné and the Atlantic Veterinary College have come up with an exciting new approach to validating tests at an international level of acceptance.”
Testing and Surveillance for Viral Hemorrhagic Septicemia Virus (VHSV)
At the Pacific Biological Station (PBS) in Nanaimo, B.C., Fisheries and Oceans Canada research scientist Dr. Kyle Garver has developed a new test for Viral Hemorrhagic Septicemia Virus to overcome the limitations of other tests, including unsuitability for massive testing. Viral Hemorrhagic Septicemia Virus is a deadly fish virus in the Great Lakes that is causing massive mortalities in many fish species and is rapidly increasing its distribution to other waterways.
Dr. Garver developed a genetics-based test (Viral Hemorrhagic Septicemia Virus quantitative reverse transcription polymerase chain reaction or VHSV RT-qPCR) for the disease that is highly sensitive, fast and enables large numbers of samples to be screened within a few hours. In 2008, the United States Animal Health Association put a resolution forward to the U.S. Department of Agriculture that it evaluate and validate two tests for the Viral Hemorrhagic Septicemia Virus, including the one developed at the Pacific Biological Station.
In an effort to control the spread of Viral Hemorrhagic Septicemia Virus, Fisheries and Oceans Canada and the Canadian Food Inspection Agency (under the National Aquatic Animal Health Program) are conducting a surveillance program using VHSV RT-qPCR test to document the spatial distribution of the emerging pathogen and gain insight into the pathways by which the virus spreads. The surveillance is being carried out in consultation with the U.S., where a similar initiative is underway. This bilateral surveillance effort is defining the presence or absence of the Viral Hemorrhagic Septicemia Virus in aquaculture and wild freshwater fish populations in Canada and the U.S., which will restore trading-partner confidence in live fish and fish product trade from regions determined to be free of the virus.
“These and other diagnostics that are under development and validation are for regulatory purposes, whether it’s an import/export program, a domestic disease control program or internal movement between provinces,” says Dr. Wright. “So, for example, if a producer wants to import salmon eggs from another country, they first need to be tested to ensure that they are not carrying a different strain of Infectious Salmon Anaemia Virus or any other diseases.”
Other research is underway to increase information about various pathogens, including expanding knowledge of their genetic makeup and how they spread. “Another project, for example, is exploring whether harvesting mussels from waters in a region known to have oysters infected with Multinucleate Sphere X (MSX) and processing those mussels elsewhere could inadvertently spread Multinucleate Sphere X, a pathogen of major concern in oysters,” says Dr. Wright. “This type of research will enable us to provide advice to the National Aquatic and Animal Health Program regarding what does and doesn’t pose a risk in terms of spreading a particular disease.”
“Our primary thrust right now is developing diagnostics,” he adds. “In addition we’re also overseeing the development of support systems for our tests, including new advances in molecular techniques, and developing a standardized national approach to how tests are run from a quality control standpoint. All of this research is integral to protecting Canada’s aquatic resources from infectious diseases.”
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