Questions and Answers
Emamectin Benzoate (SLICE)

What is SLICE?

SLICE is a veterinary drug administered via fish feed for the treatment of developing, immature and adult stages of sea lice in farmed salmon. Sea lice attack the skin of the fish, making them more susceptible to other infections and eventually destroy muscle mass. Superficial damage on lice-infected salmon can also greatly reduce their market value for aesthetic reasons. Other treatments for sea lice are either less effective or have more severe safety and environmental considerations

Why is this a public health issue?

Sea lice infestations on salmon farms is a serious problem that is difficult to treat, as the fish become more susceptible to other diseases. Sea lice attack the surface of the fish and these infected fish if left untreated can pose a risk to other fish and may be unwholesome for human consumption. Infected fish could lead to a lack of quality food products on the market.

Are fish products monitored to verify that Health Canada’s residue limits for SLICE are respected?

As part of its responsibilities the Canadian Food Inspection Agency (CFIA) tests domestically produced and imported aquaculture products for a variety of therapeutant (drug and pesticide) residues, including SLICE, to verify that these products do not exceed the residue limits set by Health Canada. For the domestic sector, this testing is part of the CFIA's routine compliance verification of the Quality Management Program in federally registered fish processing establishments.

Is SLICE (emamectin benzoate) approved for use in Canada?

SLICE is not approved for sale in Canada. This drug is authorized for sale to veterinarians on a case-by-case basis through Health Canada’s Veterinary Drugs Directorate’s (VDD’s) Emergency Drug Release Program (EDR).

Are there any other countries that have approved SLICE for use in fish?

SLICE is approved for use in fish in many other jurisdictions including the European Union, Norway and Chile. In the United States, it is approved only as a pesticide but made available for use in fish under a program similar to Canada’s EDR program.

Did Health Canada change its policy on regarding SLICE?

Health Canada has recently amended its policy on permitted SLICE residues after completing a reassessment of available data. SLICE continues to be approved for limited use under the EDR program. Under the program, the modified Maximum Residue Limit (MRL) of 42 parts per billion (ppb) has been established. This compares to established MRLs in the European Union of 100 ppb. In addition, a revised WP has been established at 68 days from the latest treatment when used at a water temperature of 5 °C or greater.

How is this drug made available through an emergency drug release?

Aspects of the product, including efficacy, safety and environmental impact are considered before issuing an EDR to a veterinarian. The veterinarian responsible for a particular fish farm has to submit a written request to VDD for an emergency drug release. The veterinarian must specify the location of the farm, the number of fish to be treated, the size of the fish and the amount of drug required. After verifying the information, VDD will evaluate the request and may authorize the manufacturer of the drug to sell a specified quantity of a drug (e.g., SLICE) to the veterinarian to treat the infected fish. Only veterinarians can access veterinary drugs through the EDR program. The program is most often used for the treatment of companion animals, but it is sometimes used for emergencies in food-producing animals.

What is the difference between a pesticide and a drug?

Pesticides are typically added to the water for treatment of external parasites. A drug such as SLICE is administered to fish in their feed, attacks external parasites and effectively eliminates them.

Is it safe to eat salmon treated with SLICE?

The public can feel confident that salmon treated with SLICE are safe to eat. Health Canada has set stringent conditions regarding the use of SLICE in order to safeguard the safety and quality of products entering the food chain. The Canadian Food Inspection Agency routinely inspects food products to enforce safety guidelines and takes appropriate action when they have been violated.

Are there other treatments for sea lice?

Calicide is the only approved veterinary drug for sale in Canada for the treatment of developing, immature stages of sea lice on salmon, however, it is not effective against adult stages of this parasite.