Studies carried out by the National Institute of Nutrition and Seafood Research (NIFES) show that one of the most common ways of treating farmed salmon against salmon louse (a crustacean) is to give the fish medicated feed containing active components. Scientists said that emamectin benzoate is the most used active component in medicated feed of this kind, being commonly used in Norway, Scotland and Chile. Since emamectin benzoate affects salmon louse, possible toxic effects on wild living crustaceans has been in focus nationally and internationally.
The study showed that the drug used for treatment may have adverse effects on the fish during medication. Researchers at NIFES have studied the stress response in salmon that have been given a standard treatment with emamectin benzoate. Researcher Pal A. Olsvik at NIFES, told that the study showed a temporary moderate oxidative stress response, and a delayed inflammatory reaction in salmon liver.
Several of the basic metabolic processes in salmon take place in the liver, and the effect of treatment with an anti-louse drug can be measured by studying the expression of genes in liver cells. The study also said that free radicals are reactive substances which are created naturally in the metabolism of cells. They are neutralised by antioxidants. If more free radicals are created than can be neutralised by the body, oxidative stress occurs.
