Can ultraviolet-C light be used to ‘zap’ parasites on salmon?

Large numbers of hosts mean that Atlantic salmon farms are the perfect environment for parasitic sea lice to reproduce. Heavily infested fish suffer from skin injuries and stress. The industry has developed a range of methods to target lice. Existing methods are either only partially effective or have negative effects on the hosts. Because of this, the hunt is still on for the ‘silver bullet’.

In an earlier paper (Barrett et al. 2019 PMS), Luke Barrett and co-authors showed that ultraviolet-C (UVC) light sterilises salmon louse eggs before they hatch which can slow lice population growth. In this latest paper (Barrett et al. 2020 Aquaculture), we tested whether UVC light can be applied to lice on live salmon. If successful, this would pave the way for using UVC lamps in salmon farms to continuously zap lice.

Unfortunately, doses of UVC that are highly effective at preventing lice reproduction (up to 99% less) also affected the skin and sensitive eyes of salmon. UVC treatments will still be useful in combating lice, but have to be deployed in ways that don’t directly expose the host fish.