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Natural Methods To Combat Parasites


Charlotte Johnston, TheFishSite editor reports from Aquaculture Europe 2011, where John Sweetman, Alltech looked at natural means to prevent against parasites.

Sealice in salmon is an increasingly important problem. Not only is the cost of the parasite crippling producers, the presence of lice on salmon farms is limiting the development of the industry.

Mr Sweetman said that sealice account for 10 to 12 per cent of the cost of salmon production.

"It is a difficult topic to address," he said. "As we can see, sealice have a huge affect on the cost of production, but they are very difficult to treat."

The challenge is the different species of lice, the different cycles, the various locations they are found in etc.

"However the consequences of the parasite are similar - with stress on the fish and an increased cost for the farmer."

Stress on fish, increases blood pressure, can cause damage to gills, increase the opportunity for secondary diseases and weaken the immune response.

Producers should aim for disease prevention. It is well recorded that strong and healthy fish perform better.


Pathogens can enter through the skin, gills and guts - all sensitive areas. To protect them the immune system creates a mucosal barrier.

However parasitic infections reduces the mucosal areas.

Mr Sweetman has been looking at the use of yeast and algae based technology to strengthen immune barriers. Called Aquate Technology, it looks at improving overall performance.

He said that little is known about mucous cells, except that they are less dense in areas surrounding the attached parasites.

Aquate, through the use of yeast and algae can improve mucous production by 55 per cent. Increased mucous prevents parasite attachment, acting as a barrier.

Recent research carried out by Mr Sweetman demonstrated that after five weeks of use, Aquate resulted in 48.2 per cent decrease in total lice per fish. After 14 weeks these numbers had further decreased.

He said that feeding Aquate is a long term feeding strategy. If fish are not fed Aquate, effects on parasite populations can be seen immediately.

November 2011