Last winter, many farmed salmon died from winter ulcers. Now, researchers have new knowledge about salmon skin and vaccines, which may be useful for next winter. The result is an improvement in vaccination against ulcers.
“We’ve documented what everyone thought,” said the lead scientist. Christian René Karlsen de Nofima. It refers to salmon that develop skin ulcers caused by bacteria.
skin first
Nofima scientists have long been concerned about salmon skin. «It is the organ that first receives a warning that the surrounding environment is changing. The skin senses all the environmental changes that affect the fish,” said Karlsen.
Salmon can develop ulcers in cold sea water. A bacteria called Moritella viscosa It is the cause of these winter ulcers.
You can get vaccinated against this winter sore bacteria, but the problem is that the bacteria has many different strains. The vaccine works much better if it is developed using the correct strain of the bacteria, the researcher said.
Improved vaccine
Not even vaccination can keep all fish healthy. Karlsen spoke of a high development of ulcers even in fish that have been vaccinated. In a recent trial where fish with ulcers were mixed with healthy fish, 15% of the fish suffered deep ulcers and 25% suffered superficial wounds.
«The vaccine is not perfect. That’s why we have moved on to something else,” said the expert. In addition to analyzing the effects of different strains of Moritella viscosa, scientists have learned how the bacteria begins to harm the fish. «It adheres to the surface of the scales. Then it multiplies and forms a colony,” Karlsen described.
«The scales are covered with a layer of mucus. The bacteria manages to get between this layer and the scales, creating large wounds that can even reach the muscle tissue,” explained the researcher.
When a fish is vaccinated, the bacteria are first found on its scales. On the other hand, in unvaccinated fish, the bacteria penetrate deeper into the skin earlier. Currently, there are several vaccines available on the market against different strains of the bacteria. Moritella viscosa.
Read the full investigation here.
Photography: Nofima
2023-12-11 10:31:22
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