What is it?

Deltamethrin is the active ingredient in a veterinary medicine, prescribed to treat sea lice. It is a synthetic pyrethroid which mimics natural chemicals produced in certain chrysanthemum flowers. In agriculture it is used in the control of ticks and is also one of the primary ingredients found in household ant powders.

Why is it used?

It is a veterinary medicine used to treat sea lice on farmed Atlantic salmon and is administered as a bath treatment. Sea lice are naturally occurring ectoparasites that can cause harm to wild and farmed fish. With fish health and welfare the top priority for Scottish salmon farmers is necessary to use medicines alongside a selection of alternative management measures (Figure 1).

Sea lice management measures on Scottish salmon farms

How does it work?

Mode of Action: the product disrupts signals in the nervous system of lice.

How much is used?

The treatment concentration is 0.2 millimetres per cubic metre of seawater.

How is its use controlled?

Products are produced and distributed through a safe and fully traceable supply chain. All treatments are recorded.

Medicine use is a condition on environmental licences (CAR) granted and regulated by SEPA (Scottish Environmental Protection Agency), extensive modelling and monitoring is conducted on sites regularly before and during their operation to ensure the use of medicine will not have any detrimental impact on the environment.

For more information see: Sea lice and Scottish salmon farming