Ultraviolet light differentially reduces viability of fish- and fish farm-associated flavobacteria (families Flavobacteriaceae and Weeksellaceae).

Authors: KNUPP, CHRISTOPHER - Michigan State University; FAISAL, MOHAMED - Michigan State University; BRENDEN, TRAVIS - Michigan State University; SOTO, ESTEBAN - University Of California, Davis; Lafrentz, Benjamin; GRIFFIN, MATT - Mississippi State University; Wiens, Gregory - Greg; CAVENDER, WADE - Utah Division Of Wildlife Resources; VANVLIET, DANIELLE - Utah Division Of Wildlife Resources; LOCH, THOMAS - Michigan State University

Submitted to: North American Journal of Aquaculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/11/2023
Publication Date: 10/25/2023
Citation: Knupp, C., Faisal, M., Brenden, T.O., Soto, E., Lafrentz, B.R., Griffin, M.J., Wiens, G.D., Cavender, W., Van Vliet, D., Loch, T.P. 2023. Ultraviolet light differentially reduces viability of fish- and fish farm-associated flavobacteria (families Flavobacteriaceae and Weeksellaceae). North American Journal of Aquaculture. 85(4):311-323. https://doi.org/10.1002/naaq.10300.
DOI: https://doi.org/10.1002/naaq.10300

Interpretive Summary: Globally, flavobacteria are leading causes of disease-related losses in fish-farms and hatcheries. One way flavobacteria enter aquaculture facilities is via open water sources. Ultraviolet (UV) light treatment of source water has been effective in reducing the risk of disease outbreaks caused by non-flavobacteria; however, the UV dose required to inactivate flavobacteria has been understudied. Towards arming aquaculture personnel with tools to enhance facility biosecurity and reduce the risk of flavobacterial epizootics, we examined the efficacy of UV light treatments by exposing 65 flavobacterial isolates, including well-known and emerging Flavobacterium and Chryseobacterium spp., in a planktonic form to low and high UV doses. All assayed flavobacteria were reduced by an average of ~1,000-fold or ~100,000-fold at the low and high UV doses, respectively; however, substantial differences in reduction at the same UV dose were noted among isolates of the same flavobacterial species, including Flavobacterium psychrophilum, F. columnare, and F. oreochromis. Overall, results demonstrate that viable flavobacteria can be reduced substantially by UV, thereby representing a promising tool for minimizing flavobacterial loads in hatcheries and aquaculture facilities.

Technical Abstract: Globally, flavobacteria (Family Flavobacteriaceae and Weeksellaceae) are leading causes of disease-related losses in fish-farms and hatcheries. One route flavobacteria use to gain access to aquaculture facilities is via source water. Ultraviolet (UV) light treatment of source water has been effective in reducing the risk of disease outbreaks caused by non-flavobacteria; however, the UV dose required to inactivate flavobacteria has been understudied. Here, we examined the efficacy of UV light treatments by exposing 65 flavobacterial isolates, including well-known and emerging Flavobacterium and Chryseobacterium spp., in a planktonic form to low (25 mJ/cm2) and high (126 mJ/cm2) UV doses using a collimating beam apparatus. All assayed flavobacteria were reduced by an average of ~1,000-fold or ~100,000-fold at the low and high UV doses, respectively; however, substantial differences in reduction at the same UV dose were noted among isolates of the same flavobacterial species, including Flavobacterium psychrophilum, F. columnare, and F. oreochromis. In addition, F. psychrophilum multilocus sequence typing variants ST10 and ST78, which are two of the most widespread variants in the U.S., were among the least susceptible to UV light. Overall, results demonstrate that viable flavobacteria can be reduced substantially by UV doses of 25 – 126 mJ/cm2, representing a promising tool for minimizing flavobacterial loads in hatcheries and aquaculture facilities, thereby enhancing biosecurity and reducing the risk of epizootics.