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The Effect of Disinfection Strategies on Transmission of Aeromonas salmonicida and Yersinia ruckeri in a Recirculating Aquaculture System

G.L. Bullocka*, W.B. Schillb
Volume 7, June 2006

The Conservation Fund Freshwater Institute
1098 Turner Road
Shepherdstown, WV 25443 USA

U.S. Geological Service
National Fish Health Research Laboratory
11649 Leetown Road
Kearneysville, WV 25430 USA

*Corresponding Author

Keywords: furunculosis, enteric redmouth disease, recirculating, biofilters, disinfection

International Journal of Recirculating Aquaculture 7 (2006). All Rights Reserved
© Copyright 2006 by Virginia Tech and Virginia Sea Grant, Blacksburg, VA USA


Continuous addition of Aeromonas salmonicida (which causes furunculosis) or Yersinia ruckeri (which causes enteric redmouth disease, or ERM) broth cultures to recirculating aquaculture systems, without fish, resulted in the presence of these pathogens in the fluidized sand biofilters. Disinfection of the recirculating systems, except biofilters, with 200 ppm sodium hypochlorite and flushing biofilters for 24 hours with filter-sterilized spring water (FSSW)did not prevent outbreaks of furunculosis or enteric redmouth disease after stocking Arctic char (Salvelinus alpinus) or rainbow trout (Oncorhynchus mykiss), respectively. Disinfection of the entire recirculating systems with 10 ppm Chloramine-T following outbreaks of furunculosis or ERM, or after addition of broth cultures prevented transmission of ERM in three trials and in two of three trials with furunculosis. Within 75 days of stocking Atlantic salmon (Salmo salar) with subclinical furunculosis in the recirculating system with rainbow trout, A. salmonicida could be cultured from the mucus of rainbow trout and from the fluidized sand biofilters. Removal of salmon and trout and disinfection of the recirculating system with 10 ppm Chloramine-T prevented a furunculosis outbreak when Arctic char were stocked into the system. However, if the recirculating system was only drained and refilled after removal of salmon and trout, furunculosis occurred within seven days of stocking char.