Location: Harry K. Dupree Stuttgart National Aquaculture Research Cntr
2015 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
Scientists initiated a study of 9 commensal bacterial isolates obtained from the skin, gill and gut of healthy hybrid striped bass. Bacteria were selected for their ability to grow under optimum conditions for Flavobacterium (F.) columnare, the bacteria responsible for columnaris disease. The isolates are being identified and screened for antagonistic effects against the pathogen. Any isolates that show these effects will then be used in vivo in a challenge with F. columnare to determine if the isolate can competitively exclude the pathogen and reduce or eliminate the disease. Any isolate found to reduce the susceptibility of fish to columnaris could potentially be used for biological control.
Scientists began a series of studies to evaluate mucosal and humoral adaptive immune responses to Flavobacterium columnare. Current studies are seeking to identify and characterize the immunogenic bacterial proteins under disease conditions. The antibody response has been characterized in multiple animals that have survived a disease challenge and a dominant antibody-response pattern to certain bacterial proteins has emerged. Studies will be conducted to establish how effective these antibodies are at protecting animals that undergo additional disease challenges.
Unit scientists initiated copper toxicity studies on 5 commercially relevant species in 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. With the range of reconstituted waters examined, this study will allow farmers to better select safe and efficacious concentrations of copper to treat their fish.
In collaboration with researchers at Auburn University, a project was started to explore the benefits of including high doses of the enzyme phytase, which degrades plant-derived phytic acid to liberate phosphorus, in commercial catfish diets. Studies are being conducted in tanks, earthen ponds, and raceways. Early results indicate that phytase inclusion into a standard ration is leading to considerable gains in feed intake and a reduced prevalence of anemia and disease.
Researchers initiated a year-long survey of water parameters typically found in production ponds in the Arkansas, Alabama, and Mississippi catfish industries. These include watershed ponds, traditional levee ponds, and split ponds. Extension professionals in each area have provided us with water samples each month. The parameters analyzed include: total and dissolved organic carbon, total and filtered chemical oxygen demand, total alkalinity, total hardness and pH. This is a collaboration with researchers at the ARS Warmwater Aquaculture Research Unit in Stoneville, MS and Auburn University. This study will allow researchers to determine baseline concentrations of parameters that may affect therapeutant effectiveness and toxicity (e.g. copper sulfate, hydrogen peroxide) to fish.
Accomplishments
1. New feed additive offers protection against columnaris disease. Flavobacterium columnare, the causative agent of columnaris disease, is among the most prevalent of all freshwater disease-causing bacteria. Scientists from Stuttgart, Arkansas, collaborated with investigators from Auburn University and demonstrated that the feeding of prepared diets (36% protein, 8% lipid) formulated with a yeast-based additive offered protection against columnaris disease when compared to the basal ration. Given the superior protection provided by the additive, investigators compared the differences in gene expression in tissues of fish fed the test diet to the standard ration. The test diet was found to reduce levels of markers of inflammation, and induced higher levels of genes related to healing and wound repair. These findings will offer producers a new means by which to combat costly columnaris outbreaks on farms.
Review Publications
Straus, D.L., Farmer, B.D., Beck, B.H., Bosworth, B.G., Torrans, E.L., Tucker, C.S. 2014. Water hardness influences Flavobacterium columnare pathogenesis in channel catfish. Aquaculture. 435:252-256.
Farmer, B.D., Straus, D.L., Beck, B.H., Kelly, A.M. 2014. The effectiveness of flow-through and/or static copper sulfate treatments on the survival of Golden Shiners and Fathead Minnows infected with Flavobacterium columare. North American Journal of Aquaculture. 77:90-95.
Liu, D., Straus, D.L., Pedersen, L., Meinelt, T. 2015. Comparison of the toxicity of the peracetic acid formulations Wofasteril(c) E400, E250 and Lspez to Daphnia magna with emphasis on the effect of hydrogen peroxide. North American Journal of Aquaculture. 77:128-135.
Meinelt, T., Phan, T., Behrens, S., Wienke, A., Pedersen, L., Liu, D., Straus, D.L. 2015. Growth inhibition of Aeromonas salmonicida and Yersinia ruckeri by disinfectants containing peracetic acid. Diseases of Aquatic Organisms. 113:207-213.
Beck, B.H., Li, C., Farmer, B.D., Barnett, L.M., Lange, M.D., Peatman, E. 2015. A comparison of high and low virulence Flavobacterium columnare strains reveals differences in iron acquisition components and responses to iron restriction. Journal of Fish Diseases. DOI: 10.1111/jfd.12343.
Zhao, H., Li, C., Beck, B.H., Zhang, R., Thongda, W., Davis, D., Peatman, E. 2015. Impact of feed additives on surface mucosal health and columnaris susceptibility in channel catfish fingerlings, Ictalurus punctatus. Fish and Shellfish Immunology. 46(2):624-637.
Peatman, E., Lange, M.D., Zhao, H., Beck, B.H. 2015. Physiology and immunology of mucosal barriers in catfish (Ictalurus spp.). Tissue Barriers. DOI: 10.1080/21688370.2015.1068907.
Beck, B.H., Peatman 2015. Mucosal Health in Aquaculture. Waltham, Ma: Academic Press. p.1-395.
Peatman, E., Beck, B.H. 2015. Why mucosal health?. In: Beck, B.H., Peatman, E., editors. Mucosal Health in Aquaculture. Waltham, MA: Academic Press. p.1-2.
Beck, B.H., Peatman, E. 2015. New frontiers in mucosal health in aquaculture. In: Beck, B.H., Peatman, E., editors. Mucosal Health in Aquaculture. Waltham, MA: Academic Press. p.371-377.
Terhune, J.S., Beck, B.H. 2015. Common diseases of black bass: implications for conservation and management. In: Tringali, M.D., Long, J.M., Birdsong, T.W., Allen, M.S., editors. Black Bass Diversity: Multidisciplinary Science for Conservation. Bethesda, MD: American Fisheries Society. p. 333-350.
