Aquatic Animal Health Science

Protecting wild and farmed aquatic species

Fisheries and Oceans Canada’s (DFO) mission is to promote economically prosperous maritime sectors and fisheries, sustainable aquatic ecosystems, and safe and secure waterways. Preventing the spread of aquatic animal diseases within Canada and guarding against the introduction of serious infectious aquatic animal pathogens (i.e., bacteria, viruses, and parasites that cause disease in aquatic animals) is critical to safeguarding the health of Canada’s aquatic resources and maintaining our export markets for fish and seafood products. DFO provides a wide range of aquatic animal health activities to support the management of our fisheries and aquaculture resources through both regulatory and non-regulatory science programs. These programs address both international aspects of aquatic animal health, as well as local health concerns of our fishery resources.

National Aquatic Animal Health Program

Canada's reputation for high quality fish and seafood depends on protecting our wild and farmed aquatic animals against serious infectious diseases. International concern for aquatic animal health has increased over the last decade as the trade in wild and farmed fresh fish and seafood product has grown worldwide and with it the increased risk of transferring serious diseases to new areas. As a member of the World Trade Organization (WTO), Canada is obliged to implement an aquatic animal health program that meets the World Organization for Animal Health (OIE) standards recognized by the WTO.

In 2005, Canada’s National Aquatic Animal Health Program (NAAHP) was implemented to be a co-delivered program between the Canadian Food Inspection Agency (CFIA), the lead regulatory and administrative authority for the program, and DFO, which provides the diagnostic testing, research, and scientific advice to support the program. Specific infectious disease agents affecting fish, molluscs, and crustaceans are covered under NAAHP.

Although the vast majority of aquatic animal pathogens pose no health risk to humans, they can be potentially devastating for wild fisheries and aquaculture operations both economically and ecologically. The CFIA is the federal lead for the NAAHP under the authority of the Health of Animals Act and the Health of Animals Regulations, which enables Canada to certify fish and seafood exports free of pathogens of international importance and to require similar health certification from countries wishing to export fish and seafood to Canada.  This prevents the transfer of pathogens of international concern from Canada to other countries, but also protects Canada from the introduction of pathogens not found here. CFIA has developed a list of reportable and notifiable pathogens affecting aquatic animals for Canada; some of the listed aquatic pathogens are endemic throughout Canada, while others only occur regionally or are exotic (foreign) to Canada.

National Aquatic Animal Health Laboratory System (NAAHLS)

Internationally recognized terrestrial and aquatic animal health programs around the world are underpinned by credible national laboratory systems which deliver accurate, reliable, and consistent test results for pathogen detection. This capability, strengthened by continuing commitments to technology development and targeted research, provides participating countries with a sound scientific foundation to protect their animal populations from the introduction of pathogens, a responsive integral domestic disease management program, and enables participating countries to defend their certification of exported animals/products.

DFO’s National Aquatic Animal Health Laboratory System (NAAHLS) was designed with this capability in mind and is comprised of four laboratories across Canada: the Pacific Biological Station (PBS), Nanaimo, BC; the Freshwater Institute (FWI), Winnipeg, MB; the Gulf Fisheries Centre (GFC), Moncton, NB; and the Charlottetown Aquatic Animal Pathogen and Biocontainment Laboratory (CAAPBL), Charlottetown, PEI. While the first three labs provide diagnostic testing and research, CAAPBL is considered a level 3 containment laboratory capable of performing research on foreign exotic pathogens. Each diagnostic testing lab is responsible for conducting pathogen testing of wild and farmed finfish, molluscs, and crustaceans for NAAHP, the Fish Health Protection Regulations (FHPR), and the National Code on Introductions and Transfers of Aquatic Organisms. Under NAAHP, CFIA currently has three wild fish and shellfish pathogen surveillance programs underway in British Columbia (Pacific Salmon and shellfish) and Québec (freshwater fish) with DFO NAAHLS conducting the diagnostic testing.  Currently, the diagnostic testing for the BC aquaculture industry is conducted outside NAAHLS.

Science and technology development are integral to Canada's performance in validating diagnostic detection methods for significant fish pathogens. Each diagnostic lab is designated as a reference lab for specific pathogens. NAAHLS is responsible for targeted research of high priority pathogens and technology development for the Centre for Aquatic Animal Health Research and Diagnostics (CAAHRD). Other programs that fund aquatic animal health research and/or require diagnostic testing can benefit from NAAHLS scientific expertise of DFO scientists and technicians, as well as laboratory facilities, such as the Program for Aquaculture Regulatory Research, the Aquaculture Collaborative Research and Development Program. DFO also conducts non-regulatory diagnostic testing for the Salmonid Enhancement Program under the Habitat and Enhancement Branch.

Fish Health Protection Regulations

The Fish Health Protection Regulations (FHPR) were created in 1977 and apply only to salmonid species (e.g., salmon, trout, and whitefish) belonging to the genera listed in Schedule I of the FHPR. The Regulations are designed to minimize the risk of spread of infectious diseases through inspection of wild and cultured fish stocks and to control the movement of infected fish between provinces/territories. They apply to live and uneviscerated dead cultured fish, eggs (including fertilized eggs or gametes) of cultured and wild fish and products of dead, uneviscerated cultured fish destined to move across provincial or territorial boundaries within Canada.  It is anticipated that these regulations will be repealed as the NAAHP is fully developed and implemented. The Regulations and Manual of Compliance were most recently revised in 2011.

Accepted Molecular Biology Testing Methods

Searching for a Unique Genetic Fingerprint

Every virus has a unique genetic fingerprint. Polymerase chain reaction (PCR) is a technique that focuses on specific portions of this fingerprint so that they may be detected and identified. Detection of this small genetic target of viral RNA constitutes a presumptive positive test result.

The PCR is a highly sensitive test that sometimes produces false positive results; because of this, these presumptive positive samples require further confirmatory testing to ensure their validity.

Confirmatory testing can take two forms: first, there should be an attempt to isolate the virus from host tissues using cell culture. Cell culture allows the virus to infect the cells and multiply as it would in the host fish. It is possible to have a positive PCR test and ultimately a negative cell culture result. Cell culture also requires that a minimum dose of live virus be present in the test sample and can take up to four weeks to have results from this test.

And secondly, the virus needs to be properly identified and this is usually done using conventional PCR techniques to amplify larger and different portions of viral genes which are then sequenced and compared to a unique fingerprint.

Tissue Quality

There are several factors which must be considered in the testing.

First, the nature of the PCR test requires the sample to be fresh or well preserved. Fish should be collected live, moribund, or as fresh mortalities (within 24 hours). Because both host (fish) and viral RNA degrades rapidly after death, virus detection can quickly become impossible by PCR or any other accepted test methods. Fish can be frozen to preserve the RNA, but tissue and virus degradation occurs even at -20 degrees Celsius. Storage at -70 degrees Celsius, or in a specialized storage preservative known as an "RNAlater," is required for long term preservation.

Second, because the virus is not distributed equally in all parts of the fish, the heart and kidney are the best organs to test. Gills can also be tested. However detection in gills can indicate viral particles are in the environment. It does not mean infection of the host. Finally, sample size should be large enough for testing. A sample the size of a grain of rice allows for both PCR & molecular confirmatory tests (sequencing). Significantly larger amounts are needed for cell culture and archiving for future reference and testing.

Because RNA degrades rapidly, an extra test, called the "reference gene assay", is conducted on the original extract. The result of this assay indicates the level of degradation by comparing it to a well preserved sample of the same species. As mentioned, if the RNA has substantially degraded, neither a PCR nor any other approved testing method can determine the presence or absence of the virus with any degree of confidence.