Bacteria bath ‘improves fish health and reduces lice’

Stembiont, produced by Norwegian biotech company Previwo, is based on 35 years of research into bacteria in water associated with salmon infections and contains a mixture of the bacteria Aliivibrio balderis and Aliivibrio njordis.

The bacteria were identified by Professor Henning Sørum of the Norwegian University of Life Sciences (NMBU), who co-founded Previwo with business incubator Kjeller Innovation in 2013.

Specific bacteria

“The product is liquid and can be added to the water at strategic points during the juvenile phase,” said Karoline Skaar Amthor, a veterinarian and Previwo’s head of technical and commercial development. 

Skaar Amthor told Fish Farming Expert’s Norwegian sister site, Kyst.no, that there are several bacteria with similar effect, and the company plans to launch more products in the future.

“The treatment is intended to ensure the presence of the specific bacteria, which are then absorbed in the fish,” said Skaar Amthor.

Production focus 

She said that the aquaculture industry has undergone rapid growth and that the focus has been on streamlining the production cycle of salmon.

“The industry has had a major focus on biosafety, and there have been several ways of producing juvenile fish. Biosafety measures to ensure that disease-causing organisms do not enter the plant are undoubtedly important,” said Skaar Amthor.

However, an almost unilateral focus on washing, disinfection and UV treatment of seawater had led to the removal of many bacteria that are important to the fish, she pointed out.

Increase in growth

The company has previously claimed that the product helps to reduce the development of wounds in salmon. Now it says it has also observed an increase in growth of treated fish and that the salmon appear to have less lice spread. The reason is that the bacteria appear to have an effect through the mucus layer of the fish.  

Do you know anything about why the bacteria have an effect through the mucus layer?

“The exact mechanisms behind it, we’re not quite sure yet,” said Skaar Amthor. “We have run several infestation trials and we see that salmon lice adhere to a lesser extent to bacteria treated fish, up to five and a half months after being infected with salmon lice.”

She added that the effect on the mucus layer appears to persist.  

“We are working to find the mechanisms. But so far we have run many trials and see the same trend on a large scale.”

Previwo general manager Kira Salonius said the company had also observed that some lice that attach themselves to fish treated with the bacterial mix produced underdeveloped egg strands.  

According to Skaar Amthor, using bacteria in the juvenile phase is something that has not been done before. 

“So, this is basically controversial and new knowledge.”

In what way is the knowledge controversial?

“Because we have not understood how close the dynamics are between bacteria in the water and the fish,” said the veterinarian.

Interaction overlooked

“We have seen the skin as an almost absolute barrier between the fish’s interior and the fish’s exterior. But we see through our research that this is to a greater extent a communication centre, precisely for bacteria.”

She added that bacteria have been on the planet much longer than humans and salmon, and that we have evolved together with the bacteria.

“The fact that we have overlooked this interaction for a very long time, I think has contributed to much of the complex disease picture that we see in the aquaculture industry today,” said Skaar Amthor.

‘A little scepticism’

What feedback have you received and are many people sceptical?

“There’s a little scepticism,” confirmed Skaar Amthor. “First of all, when you come up with a new product, the requirement is for documentation, of course. Customers also want to know why it works.”

Skaar Amthor said documenting the effect of the product on a large scale is demanding because there are several factors that can play a part, both in terms of fish biology and because the product has a preventive effect.

She added: “There has also been some scepticism about this with probiotics. Many people think of Biola (a Norwegian yoghurt brand containing active Lactobacillus) and digestion. We are working a bit on a market that is naturally immature to a new concept and that is not used to thinking of bacteria as something important. One thinks very easily of bacteria for something that causes illness.”

Chile and Canada

Skaar Amthor adds that scepticism in the market is healthy and that several fish farmers want to follow the preventive measure over time to gauge the cost-benefit effect.

Previwo is not only targeting the Norwegian market. Its product launch at The Salmon visitor centre in Oslo was streamed live to Chile, and it also presented its work at the International Symposium of Aquatic Animal Health in Charlottetown, Prince Edward Island, Canada last September.

“The company has a focus on its commercial partners in Norway, but as the first-to-launch product is applicable in all regions where Atlantic salmon are farmed, it is unconstrained by geography. Chile and Canada are potential markets for geographic expansion, and the company plans to make market entry in those regions within the next year,” Previwo stated on its website.