Development of peracetic acid-based treatment for amoebic gill disease in salmon
1.Purpose
The overall aim of the experiments described in this application is to develop an alternative treatment for amoebic gill disease (AGD). The trials will evaluate the efficacy of peracetic acid (PAA) in treating AGD and document how the treatment affects the physiology of Atlantic salmon post-smolts.
2.Distress
AGD will be induced in salmon smolts by bath exposure to Neoparamoeba perurans, the causative agent of the disease. In the first trial, treatments will be performed at two levels of infection – when gill score reaches 0.5/1 and when it reaches gill score 2/3. Two treatment protocols will be employed, bath exposure to 5 ppm PAA either for 30 mins or 1 hr. Three PAA trade products will be used. Untreated fish will serve as control. The fish will be allowed to recover for 2 weeks. Tissue sampling will be performed at defined sampling points, where fish for sampling will be humanely euthanised.
The second trial, infected/uninfected fish will be exposed to two crowding levels before PAA treatment. The treatment protocol to be used in this experiment will depend on trial 1. Fish will be humanely euthanised at pre-defined time-points for tissue collection.
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 chemotherapy will be established in an evidence-driven strategy. 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 2340 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. In addition, hypotheses from two projects are combined into one in vivo trial to reduce the number of fish for experiment.
The overall aim of the experiments described in this application is to develop an alternative treatment for amoebic gill disease (AGD). The trials will evaluate the efficacy of peracetic acid (PAA) in treating AGD and document how the treatment affects the physiology of Atlantic salmon post-smolts.
2.Distress
AGD will be induced in salmon smolts by bath exposure to Neoparamoeba perurans, the causative agent of the disease. In the first trial, treatments will be performed at two levels of infection – when gill score reaches 0.5/1 and when it reaches gill score 2/3. Two treatment protocols will be employed, bath exposure to 5 ppm PAA either for 30 mins or 1 hr. Three PAA trade products will be used. Untreated fish will serve as control. The fish will be allowed to recover for 2 weeks. Tissue sampling will be performed at defined sampling points, where fish for sampling will be humanely euthanised.
The second trial, infected/uninfected fish will be exposed to two crowding levels before PAA treatment. The treatment protocol to be used in this experiment will depend on trial 1. Fish will be humanely euthanised at pre-defined time-points for tissue collection.
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 chemotherapy will be established in an evidence-driven strategy. 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 2340 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. In addition, hypotheses from two projects are combined into one in vivo trial to reduce the number of fish for experiment.
Etterevaluering
Betydelig belastende.
Begrunnelse for etterevalueringen
The experiment provided the first empirical evidence on the use of PAA as a treatment for AGD in salmon. AGD caused physiological changes in fish including altered mucosal transcriptome and circulating metabolome. The molecules identified were crucial for the immune responses of the fish during infection. Treatment with PAA further resulted in physiological alterations. PAA did not fully treated the AGD infected fish. However, the treatment delayed the severity in the progression of the disease. Signs of histological recovery were documented as well, particularly lessening of branchial hyperplasia, which was a classic AGD pathology.
Around 75% of the fish used in the trial were experimentally infected with AGD. Most the fish prior to termination exhibited gill score between 2-3. Crowding did not significantly influence the progression of AGD.
The trial can be further improved by developing a more standardised stress protocol that will expose the fish to the same level of stress, and a more structured humane endpoint scoresheet.
Around 75% of the fish used in the trial were experimentally infected with AGD. Most the fish prior to termination exhibited gill score between 2-3. Crowding did not significantly influence the progression of AGD.
The trial can be further improved by developing a more standardised stress protocol that will expose the fish to the same level of stress, and a more structured humane endpoint scoresheet.