Not since 1999 have so few salmon been treated for lice with medicines

This is shown by the annual statistics that the Norwegian Institute of Public Health (NIPH) presents on the basis of reports from pharmaceutical wholesalers and feed companies.

The Institute of Public Health is also collaborating with the NMBU Faculty of Veterinary Medicine in the preparation of the statistics.

In its report, the NIPH points out that the use of medicines against salmon lice has varied greatly in the period 2016–2025. Consumption was highest early in the period, was significantly reduced in 2017–2019, and has since stabilised.

– From 2024 to 2025 we see a further decline, and two of the products were not used at all (imidacloprid and teflubenzuron), they write.

The fact that the use of products against salmon lice has been lower in recent years is due to control being shifted towards removal of the parasites using other methods, such as the use of cleaner fish, warm water, fresh water and mechanical removal. Non‑medicinal control methods now account for the largest share of treatments against lice.

Lowest since 1999

The total number of treatment doses – that is, the number of tonnes of salmonids that were treated with chemical delousing agents – was in 2025 significantly lower than in 2024, with a decrease of 28%.

"This is the lowest level recorded since 1999, before resistance became a widespread problem. At the same time, there was a sharp increase in the production of salmon and trout from 2024 to 2025, which further reinforces the picture of a decline in the use of chemical delousing agents," they write.

 Use discontinued

Imidacloprid was granted marketing authorisation in 2021, and use of this product more than doubled from 2021 to 2022. Imidacloprid is only to be used as a delousing agent in bath treatment in wellboats, with subsequent purification of the treatment water before discharge.

“Due to the high costs associated with this treatment, its use has been put on hold. There was therefore a significant reduction in sales in 2024, and in 2025 no sales of imidacloprid were reported,” writes NIPH.

Sales of azamethiphos were reduced by more than 30% from 2024 to 2025. While sales of diflubenzuron almost doubled from 2023 to 2024, they fell by 14% from 2024 to 2025.

Teflubenzuron was deregistered in October 2024, and there were no reported sales in 2025.

Sales of emamectin and hydrogen peroxide were reduced by 25% and 28% respectively from 2024, while sales of deltamethrin have remained stably low over the past three years.

Antibacterial agents

As the table below shows, sales of antibiotics for farmed fish have varied in the period 2016–2025.

“Sales are very low, and small variations in disease outbreaks can therefore produce noticeable changes in the statistics.”, writes NIPH.

The use of vaccines against bacterial diseases in farmed fish has been an important contributor to the low use of antibiotics. This has been the situation since the early 1990s, when the first vaccines came onto the market.

In the period 2016–2025, only two active substances have been in use: florfenicol and oxolinic acid, where oxolinic acid accounts for a small share (<0.5% in 2025).

In relation to the biomass of farmed fish produced, the changes in sales have been marginal.

Some of the medicines have been used to treat cleaner fish, but the number of antibiotic treatments of cleaner fish has been greatly reduced.

The increased consumption in 2024 was largely due to individual treatments of halibut and cod. In 2025, sales had normalised compared with previous years.

• Read the full medicines statistics on FHI’s website