Spironucleus salmonicida is a parasite that poses a threat to farmed salmon at sea, often originating in freshwater hatcheries where it has proven difficult to eliminate. New research, however, demonstrates that proper use of UV light can effectively eradicate this rare but harmful parasite.
Norwegian researchers at Nofima tested two types of UV lamps—low-pressure and medium-pressure—in controlled laboratory trials. Parasites were exposed to various UV doses, and their survival post-treatment was examined. The findings revealed that medium-pressure lamps were significantly more effective than low-pressure lamps, even at lower doses.
“With medium-pressure lamps, we observed no surviving parasites at a dose of 50 mJ/cm² or higher,” said Lill-Heidi Johansen, research manager at Nofima. At lower doses of 10 and 25 mJ/cm², the parasites were weakened to the point of dying within 48 hours.
Based on the results, researchers recommend a UV dose of at least 50 mJ/cm² when using medium-pressure lamps in hatchery systems. “However, the dose should be adjusted according to water quality, as higher organic material levels can reduce UV effectiveness,” Johansen noted.
Effective control of Spironucleus salmonicida promises healthier fish and improved production outcomes. “This provides us with a new tool in the fight against this troublesome parasite,” Johansen added.
Future studies will focus on fish trials involving Spironucleus salmonicida infections in recirculating aquaculture systems (RAS) at the Fish Health Laboratory at the Aquaculture Station in Tromsø. The effective UV dose of 50 mJ/cm² identified in initial tests will be evaluated further, alongside ozone treatment.
Researchers will also study the parasite's location within the RAS system. “Understanding where the parasite resides in the system is critical for developing the best possible disinfection strategies,” said Carlo Lazado, senior researcher overseeing the upcoming trial.
The research project is funded by the Norwegian Seafood Research Fund (FHF) and led by the Institute of Marine Research.
