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Therapeutant use in aquaculture - Questions and answers

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This document provides general information that may be useful for fish and seafood businesses when developing preventive control measures to address hazards associated with the presence of therapeutants in fish and crustaceans from aquaculture.


What are therapeutants and why are they used in aquaculture?

Therapeutants are chemical substances used on fish farms or aquaculture operations when necessary to keep aquatic animals (i.e. fish or crustaceans) healthy while they are being raised. Therapeutants could be drugs or pesticides.

In Canada, therapeutants are prescribed by licensed veterinarians after they have diagnosed health problems in aquatic animals under their care. Veterinarians are responsible for treatment using the prescribed therapeutant on the fish farm and are also involved with the aquaculture operator to ensure that the treated fish or crustaceans are safe for human consumption.

While other countries may have different procedures for administrating therapeutants, the final fish product imported into Canada must be safe for human consumption.

What is a veterinary drug?

A veterinary drug is a therapeutant that is used to treat a disease in aquatic animals and is usually given to them to consume (for example, through medicated feed). However, some drugs may be given by injection. At this moment, most aquaculture therapeutants in Canada are delivered through feed and are regulated by Health Canada's Veterinary Drugs Directorate (VDD) under the Canadian Food and Drugs Act and Regulations. For more information, refer to Health Canada's Drugs in aquaculture.

What is a pesticide?

When certain therapeutants (such as some antiparasitic products) are added to the water to specifically control only external parasites (i.e. topically applied to fish by submersion in a bath), they are deemed a pesticide and are regulated under the Canadian Pest Control Products Act and Regulations. The Pest Management Regulatory Agency (PMRA) within Health Canada approves pesticides under the Pest Control Products Act. For more information refer to Health Canada's PMRA.

Key roles in food safety

Health Canada: Setting the standards

What is Health Canada's role with respect to veterinary drugs?

The Veterinary Drugs Directorate (VDD) within Health Canada is responsible for protecting human and animal health and the safety of Canada's food supply. Through the VDD, Health Canada evaluates and monitors the safety, quality and effectiveness, sets standards and promotes the prudent use of veterinary drugs administered to food-producing and companion animals. For drug products used in food-producing animals, VDD establishes mandatory withdrawal times and sets maximum residue limits (MRLs) and administrative maximum residue limits (AMRLs) for veterinary drugs after it has conducted an extensive review of data submitted by manufacturers and has assessed the veterinary drugs' safety and risk.

What is a Maximum Residue Limit (MRL)?

A Maximum Residue Limit (MRL) is an amount of drug residue present in treated aquatic animals that will not pose adverse human health effects if the food is consumed daily over a lifetime. A MRL applies to a specific tissue for a specific species. For example, sulfadiazine (in the approved drug, Tribressen 40% Powder), a drug approved for use in salmonids in Canada, could be administered to salmonids and the residual level in the edible tissues of fish offered for sale cannot exceed the MRL of 0.1 µg/g.

What is an Administrative Maximum Residue Limit (AMRL)?

The definition of an Administrative Maximum Residue Limit (AMRL) and a MRL are basically the same since the process and rigour that the VDD uses to assess the safety and risk of a veterinary drug are the same. The only difference is that, an AMRL signifies that, the Canadian legal process to publish this information in the Food and Drug Regulations, is in progress. Once the legal process is complete, the AMRL is officially known as an MRL. While their legal status differ, there is no difference between an MRL and AMRL in terms of scientific validity and thus the VDD posts a formal list of established AMRLs on its website. In this context, AMRLs can be a factor in considering if a food is acceptable for sale in Canada and considering action to be taken where the possible adulteration of foodstuffs is suspected or known.

How does Health Canada establish a MRL for a veterinary drug or expand the scope of application of an existing MRL to a new species or target tissue?

MRLs are established only after the VDD has conducted extensive reviews of data submitted by manufacturers and has determined that foods containing these veterinary drug residues up to the established levels are safe for human consumption. Health Canada's website provides additional information on the risk assessment and veterinary new drug submissions for establishing MRLs.

What if a veterinary drug, which has not been approved by Health Canada, is needed for the emergency treatment of aquatic animals in Canada?

Health Canada may provide, under the Emergency Drug Release (EDR) program, an authorization for the sale of a drug, under the Food and Drug RegulationsFootnote 1. This authorization permits the manufacturer of a new drug to sell a limited quantity of the new drug to a veterinarian.

What if a pesticide, which has not been approved by Health Canada, is needed for the emergency treatment of aquatic animals in Canada?

The Pest Management Regulatory Agency (PMRA) within Health Canada may grant emergency release permits for pesticides under the Pest Control Products Act.

What are "banned" drugs?

According to the Food and Drug RegulationsFootnote 2, banned drugs are those drugs which are prohibited for sale for administration to animals that produce food or that are intended to be consumed as food because the drug contains one of the following:

Scientific evidence has shown that exposure to these substances is unsafe for consumers. Fish and crustaceans containing any residue from these drugs are in violation of the Food and Drug RegulationsFootnote 3 and the Safe Food for Canadians Regulations and would not be permitted for sale in the Canadian market.

What are "approved" drugs in Canada?

Drugs that have a Drug Identification Number (DIN) on the label are drugs that are approved by Health Canada. The approved drugs can be found in the list of veterinary drugs that are authorized for sale by Health Canada for use in food-producing aquatic animals.

Any drug residue present in the food must not exceed the MRL or AMRL for that drug set by Health Canada.

Which therapeutants are "accepted to be used" in aquaculture in Canada?

A therapeutant "accepted to be used" in aquaculture in Canada can be either of the following:

Can I import or process fish products that contain therapeutants not "accepted to be used" in aquaculture in Canada?

No, any therapeutants which are not considered "accepted to be used" are essentially unapproved and their residues should not be present in fish offered for sale in Canada.

Where can I find a list of aquaculture therapeutants currently monitored by the Canadian Food Inspection Agency (CFIA)?

Consult the CFIA aquaculture therapeutant residue monitoring list for imported and domestically produced aquacultured products, including but not limited to, "banned" drugs and "accepted to be used" therapeutants.

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