Submitted to: Flavobacterium Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 9/16/2015
Publication Date: 10/27/2015
Citation: Straus, D.L., Farmer, B.D., Beck, B.H., Bosworth, B.G., Torrans, E.L., Tucker, C.S. 2015. Water chemistry affects catfish susceptibility to columnaris [abstract]. Flavobacterium Meeting, October 27-29, 2015, Auburn, AL. p.67.
Technical Abstract: While columnaris disease has been well-studied, little is known about how specific water chemistries can affect attachment. Recent studies in our labs offer new insight on this subject. Well waters from the USDA/ARS Stuttgart National Aquaculture Research Center (SNARC; Stuttgart, Arkansas) and from the USDA/ARS Warmwater Aquaculture Research Unit (WARU; Stoneville, Mississippi) were used. These waters were chosen because SNARC has developed an effective columnaris challenge model, but researchers at WARU have been unsuccessful at inducing columnaris in their water. In the first experiment, unfiltered well waters from SNARC and WARU were used. Fingerling channel catfish (Ictalurus punctatus) were challenged with a Flavobacterium columnare suspension in aquaria for 4 days; each aquarium contained 10 L of water and 50% was replaced daily. No fish died in the WARU water, but 100% of the fish died in SNARC water. Using qPCR, we found that there were ~1900 times more F. columnare attached to the gills of the fish in SNARC water. In the second experiment, four waters were used: the above waters, WARU water filtered through a carbon bed to remove tannins and SNARC water filtered through a water softener to remove hardness. No fish died in the WARU or filtered waters, but 17% of the fish died in SNARC water. Again using qPCR, we found that there were approximately 1600 times more F. columnare attached to the gills of the fish in SNARC water. Filtered SNARC water had less F. columnare than unfiltered SNARC water and filtered WARU water had more F. columnare than unfiltered WARU water. Results suggest tannins have minimal involvement, and water analyses suggest that calcium and hardness are two parameters influencing bacterial attachment and ultimately pathogenesis. To further investigate the mechanisms of bacterial attachment, ongoing experiments are focused on various parameters including: using only calcium or magnesium to provide hardness, fluoride content (WARU water has higher fluoride) and sodium chloride content; all of which will be discussed.