Salmon lice - resistance to chemotherapeutants

The Norwegian Veterinary Institute has a surveillance program on resistance in salmon lice towards medicines used for salmon lice treatments.

The aim of the program is to describe resistance towards and give advice on the use of these medicines.    


The number of medicinal treatments applied against salmon lice was reduced in 2017. This continued a yearly trend that started in 2015. Despite this, the level of resistance seen in salmon lice remained high in 2017. Resistance towards deltamethrin, azamethiphos and emamectin benzoate were generally widespread along the Norwegian coast. Less resistance was found towards hydrogen peroxide than towards the other medicines, but loss of sensitivity was indicated in several areas. 750 prescriptions for medicines against salmon lice were prescribed in 2017, which was a 61 percent reduction compared to 2016. The number of non-medicinal treatments increased with 47 percent, to 1,759 reported treatments, in the same time period. Non-medicinal methods for treatment and prevention were thereby the dominating methods for salmon lice control. Thermic delousing accounted for 74 percent of the non-medicinal treatments in 2017. 

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