Forsøksdyr: Treatment of amoebic gill disease-infected Atlantic salmon smolts with peracetic acid bathing

Godkjenningsdato 23.04.2020

Godkjenningsperiode 23.04.2020-25.07.2020

Currently available therapies (i.e., freshwater and hydrogen peroxide bathing) for amoebic gill disease (AGD) in salmon have several issues including efficacy, logistics, environmental risks, health and welfare, to name a few. Therefore, finding an alternative that can address these challenges is timely and relevant. This trial will evaluate the efficacy of peracetic acid (PAA) in treating AGD and document how the treatment affects the physiology of Atlantic salmon post-smolts.

AGD will be induced in salmon smolts by bath exposure to Neoparamoeba perurans, the causative agent of the disease. Once the gill macroscopic score reaches 2/3, the experimental fish will be treated by bath exposure to PAA for 30 minutes. Two nominal concentrations will be tested: 5 and 10 ppm. Untreated fish will serve as control. The fish will be allowed to recover for 4 weeks. Tissue sampling will be performed at defined sampling points, where fish for sampling will be humanely euthanised. After the recovery period, the remaining fish will be exposed to a crowding challenge by increasing the density in the tank by 5x. A post-stress plasma sampling will be performed thereafter.

3.Expected benefit
The trial described in this application is expected to offer the salmon aquaculture industry an alternative treatment against AGD that is safe, effective and sustainable. Moreover, the potential of the proposed chemotherapy will be established in an evidence-driven approach. This trial is part of a project that employs an integrative and holistic strategy in developing a chemotherapy for AGD, i.e., several aspects of treatment is explored including efficacy, environmental risk and health and welfare impacts.

4.Number of animals, and what kind
The trial will use 720 Atlantic salmon smolts reared in full-strength seawater (35 ppt).

5.How to adhere to 3R
There is no other way to test the hypothesis in the study than performing a trial using live fish. However, the experiment has been designed in such a way that the number of fish is reduced to a minimum, i.e., minimum stocking density in the tank. Moreover, several hypotheses have been combined in one trial to maximize the outputs from the experiment.