Location: Harry K. Dupree Stuttgart National Aquaculture Research Cntr
2016 Annual Report
Objectives
Objective 1. Characterize the cellular and molecular immune responses governing resistance/susceptibility to infectious disease (Flavobacterium columnare), and develop strategies to enhance immune protection through immunomodulatory compounds, nutritional status, or water chemistry.
Subobjective 1A. Describe the cellular, transcriptional, and pathological responses of mucosal tissues in healthy and Flavobacterium columnare-challenged fish.
Subobjective 1B. Investigate the effects of copper sulfate, short-term feed deprivation, and water chemistry on the mucosal immune system.
Objective 2. Assess microbial community diversity, prevalence, and distribution under homeostatic conditions, after columnaris disease challenge, and following environmental perturbation.
Subobjective 2A. Profile the composition and population dynamics of microbes that reside on the skin and gill of healthy and columnaris-challenged fish.
Subobjective 2B. Investigate the effects of copper sulfate, short-term feed deprivation, and water chemistry on microbial community composition.
Approach
In Objective 1 our research team will utilize next-generation sequencing to establish temporal profiles of transcriptional responses to Flavobacterium (F.) columnare in gill and skin; use flow cytometry to monitor the type and abundance of immune cells trafficking to the gill of challenged fish; and characterize the histopathological changes to an F. columnare challenge and draw parallels to the shifts in immune-related transcripts and cell phenotypes. Studies will also examine the transcriptional and immunological consequences to alterations in water chemistry and to chemical compounds such as copper sulfate. In Objective 2 the core microbiota associated with mucosa in healthy fish and F. columnare infected fish will be characterized using using high-throughput 16S v4 amplicon sequencing. This work will identify the core microbial communities commonly residing in the mucosal barriers of both warmwater bass and channel catfish; vital information towards identifying bacterial species that can be exploited to improve fish health.
Progress Report
Unit scientists continue to pursue studies that will identify F. columnare mechanisms of infectivity. Current studies are underway to characterize the formation of biofilms by F. columnare. These biofilms appear to be important in pathogenesis of the host, and therefore could be an important target for immune protection. Studies to better understand biofilm formation under different in vitro and in vivo environmental conditions continue to be conducted. This work will lead to better therapies in industry for columnaris disease.
Scientists continued copper sulfate toxicity studies to various species of fish in 5 reconstituted waters ranging from very soft to very hard. These tests will determine the LC50 (acute toxicity) as well as the highest concentration of copper that does not cause mortality. This study will be important to many farmers in the industry to understand the amount copper sulfate they can use to treat their fish.
Scientists completed a year-long survey of water parameters typically found in 20 production ponds (watershed ponds, traditional levy ponds, or split ponds) in the Arkansas, Alabama and Mississippi catfish industries. The parameters include: total and dissolved organic carbon, total and filtered chemical oxygen demand, total alkalinity, total hardness and pH. We are collaborating with researchers at the ARS lab in Stoneville, MS and Auburn University to publish the results. This study was undertaken to determine baseline concentrations of parameters that may affect therapeutant effectiveness and toxicity (e.g. copper sulfate, hydrogen peroxide) to fish.
Studies to determine the minimum amount of calcium that is needed in reconstituted water for F. columnare to attach to gills of channel catfish are being conducted. This work is being done in collaboration with researchers at the Warmwater Aquaculture Research Center Stoneville, MS.
A collaboration with scientists at Bowling Green State University (Bowling Green, OH) and The Freshwater Institute (Shepherdstown, WV) to quantify the amount of Saprolegnia spp. in recirculating aquaculture systems and to treat them with peracetic acid to prevent Saprolegnia.
Scientists continue studies to evaluate mucosal and humoral adaptive immune responses to F. columnare. Previous work identified dominant epitopes in the adaptive immune response to F. columnare, which led to the identification of a single dominant protein in the humoral response. We continue to conduct studies to establish how effective these targets are at generating protective antibodies, and evaluating animals for protection from additional bacterial challenges.
Accomplishments
None.
Review Publications
Straus, D.L., Farmer, B.D., Ledbetter, C.K., Beck, B.H., Williams, R.S., Clark, M.L., Freeze, M.T. 2016. Use of copper sulfate to control Saprolegniasis at a commercial sunshine bass hatchery. North American Journal of Aquaculture. 78:243-250.
Lange, M.D., Beck, B.H., Brown, J.D., Farmer, B.D., Barnett, L.M., Webster, C.D. 2016. Missing the target: DNAk is a dominant epitope in the humoral immune response of channel catfish (Ictalurus punctatus) to Flavobacterium columnare. Fish and Shellfish Immunology. 51:170-179.
Farmer, B.D., Beck, B.H., Mitchell, A.J., Rawles, S.D., Straus, D.L. 2016. Dietary copper effects survival of channel catfish challenged with Flavobacterium columnare. Aquaculture Research. 48(4):1751-1758. doi:10.1111/are.13012.
