Progress 10/01/13 to 09/30/14
Outputs
Progress Report Objectives (from AD-416): The long-term objective of this project is to characterize the pathogenesis of fish diseases and to develop approaches to control diseases in warm water fishes. Over the next 5 years, our project at the Stuttgart National Aquaculture Research Center (SNARC) will focus on the following objectives: Objective 1. Characterize genetic variation of white bass and sunshine bass resistance to columnaris and develop strategies to control columnaris in warm water aquaculture. Subobjective 1A. Develop a Flavobacterium columnare disease model in white bass (Morone chrysops) and sunshine bass (female Morone chrysops x male M. saxitalis). Determine whether there is genetic variation for survival of white bass and sunshine bass in response to columnaris infection (Darwish and Mitchell). Subobjective 1B. Characterize Flavobacterium columnare virulence genes using real-time PCR to evaluate gene expression (Straus). Objective 2. Evaluate compounds and methods to treat bacterial and fungal (columnaris, streptococcosis, and saprolegniasis) fish diseases. Subobjective 2A. Control columnaris in channel catfish with copper sulfate (Darwish, Mitchell, and Straus). Subobjective 2B. Control saprolegniasis on channel catfish eggs and improving hatch rate by chemical means (Mitchell and Straus). Subobjective 2C. Evaluate caprylic acid to control streptococcosis in sunshine bass (Darwish). These objectives are designed to address current research concerns of stakeholders and will help in the ultimate goal of better treatments for disease epizootics resulting in higher profits for producers. Approach (from AD-416): Objective 1. An infection method will be developed for white bass and sunshine bass to produce consistent mortalities similar to a natural infection of the bacterial disease columnaris caused by F. columnare. Resistance to columnaris will be characterized in families of sunshine bass and white bass, and maternal and paternal effects will be determined. The expression level of the putative virulence genes (identified by sequence comparison) in F. columnare will be characterized to provide insight into bacterial pathogenesis. Reverse-transcriptase real-time PCR methods will be developed and used to profile the transcript level of selected genes in isolates of high and low pathogenicity. Objective 2. The efficacy of CuSO4 against columnaris will be tested in vitro using micro-dilution assays and in vivo by using four treatment levels of CuSO4 against a columnaris disease model simulating a natural infection. The scenarios used to expose channel catfish to CuSO4 prior to bacterial challenge based on previous work will consist of either pre- exposure to CuSO4 dissolved in the water or pre-exposure to CuSO4 incorporated in feed. Research will be designed to improve the effectiveness of CuSO4, H2O2, and formalin to fungi on channel catfish eggs and on the hatch rate of these eggs. A new aquaculture therapeutant (peracetic acid) will be used to treat saprolegniasis on intact channel catfish eggs in hatching troughs. The concentration of caprylic acid that inhibits the bacteria S. iniae will be determined in vitro and its potential efficacy will be assessed against an experimental S. iniae infection in sunshine bass. Since initiating this Project in November 2009, progress was made on both objectives of the parent project to address components 4b and 4c of the National Program 106-Aquaculture Action Plan. Compared the potential of static and flow-through hydrogen peroxide and copper sulfate treatments to increase channel catfish egg survival and prevent fungal growth on eggs; hydrogen peroxide static treatments proved best. Completed the development of a low-flow water delivery system for columnaris challenge testing. High levels of ammonia in water were shown to lower fish mortality in fish infected with bacteria, contrary to the generally accepted view that ammonia increases mortality in infected fish. (Obj 2) Investigated the therapeutic value of copper sulfate against an acute columnaris infection in channel catfish; fish challenged with Flavobacterium columnare and treated by waterborne exposure to copper sulfate (4.2 and 2.1 mg/L) had reduced mortalities compared to non- treated fish. Evaluated the efficacy of florfenicol, copper sulfate, amd potassium permanganate in controlling infections of Aeromonas hydrophila and F. columnare in sunshine bass; florfenicol and copper sulfate were demonstrated to increase the survival rate. The microbiology laboratory participated by invitation in an international multi-laboratory study to establish the expected drug sensitivity ranges of the quality control bacteria Escherichia coli (ATCC25922) and Aeromonas salmonicida (ATCC33658). (Obj 1 & 2) Designed a primer set and fluorescent probe to amplify the 16S ribosomal gene of F. columnare to be used as an internal control for virulence gene expression. Completed the in-life phase of a safety study to demonstrate that the proposed recommended daily treatment of 17a-methyltestosterone (9 mg/kg fish body weight) and 3 or 5 times the recommended treatment for 28 days were safe for treating tilapia. Evaluated peracetic acid, copper sulfate, and potassium permanganate to control Ichthyobodo necator; copper sulfate was the best treatment. Completed testing on acute toxicity of CuSO4 to Ich theronts in reconstituted waters (6225-32000-005- 03N). Evaluated peracetic acid for fungus control on catfish egg masses in a flow-through system; 2.5 mg/L twice a day prevented fungus from growing and destroying the eggs (6225-32000-005-04N). (Obj 1) Compared the potential of static and flow-through peracetic acid (PAA) treatments to increase channel catfish egg survival and prevent fungal growth on eggs in a hatchery setting; static treatments required the lowest concentration of PAA, but turning water off in hatcheries would not be a practical application (6225-32000-005-04N). Determined the acute toxicity of PAA to channel catfish fry; PAA was safer to use on newly hatched fry than on fry that were about 9 days old, but there was very low toxicity (6225-32000-005-04N). Collaborated on a study to develop data on the use of PAA to reduce growth rates of Flavobacterium columnare and Saprolegnia parasitica in culture (6225-32000-005-04N). (Obj 2) We used the previously developed low-flow water delivery system to study the disease progression of columnaris in sunshine bass to produce consistent infections and study immune response characteristics; samples were taken to understand the molecular mechanisms of the disease and to observe any cellular changes. (Obj 1) Determined copper sulfate was more effective than potassium permanganate in lowering fish mortality in catfish naturally infected with columnaris, contrary to the generally accepted view that potassium permanganate is the best treatment. (Obj 1 & 2) The efficacy of Aquaflor(R), copper sulfate, and potassium permanganate in controlling infections of Aeromonas hydrophila and F. columnare in sunshine bass was evaluated; Aquaflor and copper sulfate were demonstrated to increase survival. (Obj 1 & 2) Determined the length of time a parasite (Bolbophorus damnificus) can persist in channel catfish; this study outlined the potential severity of an infection. (Obj 2) Collaborated on a study to determine the bioaccumulation of copper in red drum tissues after prescribed treatments to control external parasites (e.g., Amyloodinium sp); this study went further to define the withdrawal period so the fish can be safely returned to the food supply. (Obj 2) Used molecular methods (i.e., real-time PCR) to measure virulence gene expression in cultured Flavobacterium columnare strains and will compare this expression to samples from diseased fish; this test will predict which strain of the bacteria will cause the most severe disease. (Obj 1) Continued using molecular methods (i.e., real-time quantitative PCR) to measure virulence gene expression in cultured Flavobacterium columnare strains and will compare this expression to samples from diseased fish; this test will predict which strain(s) of bacteria will cause the most severe disease. (Obj 1) Initiated acute toxicity tests on juveniles of several species to develop a more complete understanding on use of peracetic acid in aquaculture. (Obj 2) Evaluated Flavobacterium columnare concentrations and fish densities required to produce consistent columnaris infections in white bass and in hybrid striped bass. Found that white bass genetically selected for growth are less susceptible to F. columnare than hybrid striped bass. (Obj 1) Used molecular methods to study the mechanisms of columnaris disease. Examined the role of nutritional status on RBL regulation. (Obj 1) Conducted experiments to evaluate the effects of pre-exposure of channel catfish fingerlings to copper sulfate on susceptibility to columnaris disease. Results indicate that resistance can be induced but is strongly correlated to the time between copper sulfate exposure and bacterial challenge. (Obj 1 & 2) Compared potential of copper sulfate and peracetic acid treatments to prevent fungus on hybrid striped bass eggs. Preliminary data suggests that copper sulfate is more effective than peracetic acid and results in higher survival of fry through the hatching stage (6225-32000-005-09N). (Obj 2) Prepared final study reports for completed effectiveness dose confirmation studies on using copper sulfate to control egg mortality associated with saprolegniasis infecting channel catfish eggs and are submitting these to the sponsor who will submit them to FDA (6225-32000- 005-07N). (Obj 2) Continued using molecular methods (i.e., RNA-sequencing) to measure virulence gene expression in cultured Flavobacterium columnare strains resulting in vastly different mortalities. (Obj 1) Continued acute toxicity tests on juveniles of several fish species to develop a more complete understanding on the use of peracetic acid in aquaculture. (Obj 2) Evaluated Flavobacterium columnare resistance/susceptibility in sunshine bass families. Found that survival varied by family, but not significantly, probably due to low sample size. (Obj 1) Conducted lab experiments to evaluate the effect of copper sulfate incorporated in feed on channel catfish fingerlings to study their susceptibility to columnaris disease. Results indicate that resistance can be induced. A field trial to test these results on a larger scale is currently underway. (Obj 1 & 2) Evaluated the influence of a variety of water chemistry parameters on the pathogenesis process of Flavobacterium columnare. Results suggest calcium plays a key role and further studies are planned to elucidate the effects of individual chemical components. (Obj 1) Determined the potential of copper sulfate treatments to prevent fungus on sunshine bass eggs. Concluded from the results of the study that 20 ppm copper sulfate is the target dose (6225-32000-005-09N). (Obj 2) Provided information to FDA as requested to support the previously submitted final study reports on use of copper sulfate to control fungus (saprolegniasis) infecting channel catfish eggs during the FDA review process (6225-32000-005-07N). (Obj 2) Continued acute toxicity tests on juveniles of a variety of fish species to develop a more complete understanding on the use of peracetic acid in aquaculture. (Obj 2) Evaluated the influence of well water chemistry on the pathogenesis of Flavobacterium columnare. Results suggest calcium plays a key role and further studies are planned to elucidate the effects of individual chemical components. (Obj 1) Followed up last year's lab experiments to evaluate the effect of copper sulfate incorporated in feed on channel catfish fingerlings to study their susceptibility to columnaris disease with a field study involving cooperators at Auburn University. Results of the lab study indicate that resistance can be induced. Results from the field trial will be analyzed upon completion. (Obj 1 & 2) Initiated copper toxicity tests with striped bass in reconstituted waters to determine safe baseline levels under different water quality parameters. This will lead to applicable knowledge of this toxicity to aquaculturists in a variety of settings. (Obj 2) Initiated largemouth bass egg fungus studies with a commercial producer to determine the effectiveness of copper sulfate as a fungicide. (Obj 2) Collaborated with University of Arkansas at Pine Bluff on research on the effectiveness of copper sulfate on columnaris in minnows. (Obj 1 & 2) Collaborated with the Rathbun Fish Research Center (Iowa Department of Natural Resources) concerning the use of copper sulfate in walleye culture for control of mortality from Ichthyophthirius multfiliis and columnaris. We are currently finishing a study on growth inhibition after copper treatment at SNARC. (Obj 2) Collaborated with the Andrew H. Hulsey Hatchery (Arkansas Game and Fish Commission) on the safe use of copper sulfate on egg fungus and its toxicity to fish. (Obj 2) Accomplishments 01 Powerful genomic resources developed for blue catfish. The blue catfish, Ictalurus furcatus, is native to North America and serves as the paternal species of the blue x channel catfish hybrid that is valued for U.S. aquaculture production. Little was known about the extent of genetic diversity in blue catfish, which has impeded genetic selection/improvement in this species. ARS scientists in Stuttgart, Arkansas, and Stoneville, Mississippi, collaborated with Auburn University researchers and used a method termed Genotyping-by- Sequencing to obtain DNA sequences from individuals of five wild and domesticated blue catfish populations, and then aligned those sequences to identify DNA sequence variation between individuals. The analysis resulted in nearly 5000 single nucleotide differences across all five populations, and population genetic analyses also revealed potential shared ancestry between populations. This research resulted in an initial assessment of the relatedness of blue catfish populations that can be used for hybrid catfish production, and also resulted in highly informative DNA markers useful for parentage and kinship determination in blue catfish and hybrid catfish families. 02 New insight on the chemical messengers of the immune response. Cytokines are a diverse group of proteins that are important in the immune response to infectious microorganisms. One family of cytokines is the interleukin-17 family, which has been linked to immune protection against certain diseases in humans. In this study, ARS researchers at Stuttgart, Arkansas, characterized the diversity and levels of IL-17 and IL-17 receptors in the tissues of healthy channel catfish, and after exposure to Edwardsiella ictaluri and Flavobacterium columnare, the two most costly and problematic pathogens of the U.S. farmed catfish industry. They found that channel catfish had seven different types of IL-17 genes and four unique IL-17 receptors, both of which varied by tissue type and changed very rapidly after infection. This initial description of the IL-17 family in channel catfish sets the stage for future studies examining the role of the IL-17 system in the defense against these important bacterial diseases of farm-raised channel catfish. 03 Columnaris disease receptor diversity identified. Rhamnose binding- lectins (RBLs) are a family of molecules that have important functions in the immune system of fish. Previously, investigators in Stuttgart, Arkansas, found that fish highly susceptible to infection with Flavobacterium columnare, the causative agent of columnaris disease, had higher RBL levels in tissues such as the gill. In this study, we wanted to better understand the function of RBLs and to identify how many unique RBLs were present in channel catfish. We identified six different types of RBLs and examined how their levels responded to infection with columnaris disease and enteric septicemia of catfish, two bacterial diseases of commercial importance. The levels of each RBL varied widely between the two bacterial diseases. Also, the pattern of RBL expression was different between the various tissues examined. These findings suggest that each RBL may play a unique role in the host immune response to bacteria. Our findings improve our understanding of the immune system of cultured fish, and will help in identifying new preventatives and treatments for costly diseases.
Impacts
(N/A)
Publications
- Farmer, B.D., Mitchell, A.J., Straus, D.L., Beck, B.H., Fuller, S.A. 2014. Comparative effects of copper sulfate or potassium permanganate on channel catfish concurrently infected with Flavobacterium columnare and Ichthyobodo necator. Journal of Applied Aquaculture. 26:71�83.
- Wang, X., Li, C., Thongda, W., Luo, Y., Beck, B.H., Peatman, E. 2014. Characterization and mucosal responses of interleukin 17 family ligand and receptor genes in channel catfish Ictalurus punctatus. Fish and Shellfish Immunology. 38:47-55.
- Liu, D., Steinberg, C.E., Straus, D.L., Pedersen, L., Meinelt, T. 2014. Salinity, water hardness, and dissolved organic carbon modulate degradation of peracetic acid (PAA) compounds in aqueous solutions. Aquacultural Engineering. 60:35-40.
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Progress 10/01/12 to 09/30/13
Outputs
Progress Report Objectives (from AD-416): The long-term objective of this project is to characterize the pathogenesis of fish diseases and to develop approaches to control diseases in warm water fishes. Over the next 5 years, our project at the Stuttgart National Aquaculture Research Center (SNARC) will focus on the following objectives: Objective 1. Characterize genetic variation of white bass and sunshine bass resistance to columnaris and develop strategies to control columnaris in warm water aquaculture. Subobjective 1A. Develop a Flavobacterium columnare disease model in white bass (Morone chrysops) and sunshine bass (female Morone chrysops x male M. saxitalis). Determine whether there is genetic variation for survival of white bass and sunshine bass in response to columnaris infection (Darwish and Mitchell). Subobjective 1B. Characterize Flavobacterium columnare virulence genes using real-time PCR to evaluate gene expression (Straus). Objective 2. Evaluate compounds and methods to treat bacterial and fungal (columnaris, streptococcosis, and saprolegniasis) fish diseases. Subobjective 2A. Control columnaris in channel catfish with copper sulfate (Darwish, Mitchell, and Straus). Subobjective 2B. Control saprolegniasis on channel catfish eggs and improving hatch rate by chemical means (Mitchell and Straus). Subobjective 2C. Evaluate caprylic acid to control streptococcosis in sunshine bass (Darwish). These objectives are designed to address current research concerns of stakeholders and will help in the ultimate goal of better treatments for disease epizootics resulting in higher profits for producers. Approach (from AD-416): Objective 1. An infection method will be developed for white bass and sunshine bass to produce consistent mortalities similar to a natural infection of the bacterial disease columnaris caused by F. columnare. Resistance to columnaris will be characterized in families of sunshine bass and white bass, and maternal and paternal effects will be determined. The expression level of the putative virulence genes (identified by sequence comparison) in F. columnare will be characterized to provide insight into bacterial pathogenesis. Reverse-transcriptase real-time PCR methods will be developed and used to profile the transcript level of selected genes in isolates of high and low pathogenicity. Objective 2. The efficacy of CuSO4 against columnaris will be tested in vitro using micro-dilution assays and in vivo by using four treatment levels of CuSO4 against a columnaris disease model simulating a natural infection. The scenarios used to expose channel catfish to CuSO4 prior to bacterial challenge based on previous work will consist of either pre- exposure to CuSO4 dissolved in the water or pre-exposure to CuSO4 incorporated in feed. Research will be designed to improve the effectiveness of CuSO4, H2O2, and formalin to fungi on channel catfish eggs and on the hatch rate of these eggs. A new aquaculture therapeutant (peracetic acid) will be used to treat saprolegniasis on intact channel catfish eggs in hatching troughs. The concentration of caprylic acid that inhibits the bacteria S. iniae will be determined in vitro and its potential efficacy will be assessed against an experimental S. iniae infection in sunshine bass. We continued acute toxicity tests on juveniles of several fish species to develop a more complete understanding on the use of peracetic acid in aquaculture. We evaluated Flavobacterium columnare resistance/susceptibility in sunshine bass families. We found that survival varied by family, but not significantly, probably due to low sample size. We conducted lab experiments to evaluate the effect of copper sulfate incorporated in feed on channel catfish fingerlings to study their susceptibility to columnaris disease. Results indicate that resistance can be induced. A field trial to test these results on a larger scale is currently underway. We evaluated the influence of a variety of water chemistry parameters on the pathogenesis process of Flavobacterium columnare. Results suggest calcium plays a key role and further studies planned to elucidate the effects of individual chemical components. We determined the potential of copper sulfate treatments to prevent fungus on sunshine bass eggs. We concluded from the results of the study that 20 ppm copper sulfate is the target dose (Subordinate project 6225- 32000-005-09N). We provided information to FDA as requested to support the previously submitted final study reports on use of copper sulfate to control fungus (saprolegniasis) infecting channel catfish eggs during the FDA review process (Subordinate project 6225-32000-005-07N). Accomplishments 01 Disease outbreak linked to water chemistry. Columnaris is a deadly fish disease that is caused by a bacteria (Flavo-bacterium columnare) that attaches to a fish's gills or skin (bacterial attachment). If we can stop the bacteria from attaching to the fish, we can prevent the fish from getting sick. Columnaris disease cannot be induced in some labs, and one possible explanation could be the water source. ARS scientists in Stuttgart, Arkansas, and Stoneville, Mississippi, found dramatic differences in catfish mortality after exposing fish to the columnaris bacteria in well-water from the two labs. Further investigation indicated bacterial attachment was 2000-fold less in softer waters with tannins. An additional study manipulated the calcium and tannin concentration in the waters to study their effects on the disease. The results suggest calcium is a key regulator of bacterial attachment. The study reveals the mechanisms of bacterial pathogenicity; this greater understanding will lead to further advances in controlling this disease. 02 Copper sulfate effectively controls fungus (Saprolegnia) and increases survival of sunshine bass eggs. Fungus in sunshine bass hatcheries can cause decreased hatch rates and decreased profits. A collaborative study with ARS scientists in Stuttgart, Arkansas, and Keo Fish Farm, Inc. (Keo, Arkansas) addressed sunshine bass egg mortality from fungal growth. This study determined the optimum concentration of copper sulfate needed to prevent fungus from destroying the eggs while allowing the hatched larvae to thrive. The impact of this accomplishment was to decrease larval mortality and reduce time and effort in the hatchery, thereby having an immediate economic benefit to the farmer with this inexpensive treatment. This provides direct benefits through increased survival rates in sunshine bass hatcheries which will economically benefit the industry; the majority of the industry is now using this treatment. 03 Analysis of the columnaris transcriptome reveals genes that mediate virulence. In lab studies, Flavobacterium columnare (the bacteria that causes columnaris disease) isolates from different fish species or different geographic regions have been shown to vary in their ability to cause disease, a characteristic termed virulence. To better understand this, ARS scientists in Stuttgart, Arkansas, and colleagues at Auburn University, Alabama, used a powerful, next-generation sequencing technology termed RNA-seq to examine thousands of genes in two isolates of the bacteria with known differences in virulence (i.e., one highly virulent and one weakly virulent). In the highly virulent isolate, genes previously shown to control virulence in human pathogens were highly upregulated. Genes and gene pathways identified were those involved in the acquisition of iron and carbohydrates, and genes that allow the bacterium to evade and protect itself from the host immune system. These findings can be used to make new columnaris disease vaccines, or improve existing vaccines, and provide scientists with a better understanding of the factors that lead to columnaris disease outbreaks in farmed fish. 04 Kaolinitic clay protects fish from columnaris disease. Columnaris disease, caused by the bacterium Flavobacterium columnare, is a costly disease of many commercially grown fish species, including channel catfish. Despite its importance, few preventatives or therapies exist for this disease. In this study, a type of clay called kaolin was evaluated for the prevention of columnaris disease. ARS scientists in Stuttgart, Arkansas, demonstrated that addition of kaolin to the water significantly improved the survival of channel catfish that were experimentally infected with the disease, and protected the gill from damage by the bacteria. Data suggests that kaolin works by binding to the bacteria, thereby preventing it from attaching to the fish and initiating disease. The impact of this accomplishment is to improve the economics of the industry by providing a novel, non-antibiotic treatment to increase survival rates in catfish hatcheries.
Impacts
(N/A)
Publications
- Marchand, P., Phan, T., Straus, D.L., Farmer, B.D., Stuber, A., Meinelt, T. 2012. Reduction of in vitro growth in Flavobacterium columnare and Saprolegnia parasitica by products containing peracetic acid. Aquaculture Research. 43:1861-1866.
- Farmer, B.D., Mitchell, A.J., Straus, D.L., Fuller, S.A., Bullard, S. 2013. Efficacy of bath treatments of formalin and copper sulfate on cultured white bass, Morone chrysops, concurrently infected by Onchocleidus mimus and Ichthyophthirius multifiliis. Journal of the World Aquaculture Society. 44(2):305-310.
- Pedersen, L., Meinelt, T., Straus, D.L. 2013. Peracetic acid degradation in freshwater aquaculture systems and possible practical implications. Aquacultural Engineering. 53:65-71.
- Straus, D.L., Bowker, J.D., Bowman, M.P., Carty, D., Mitchell, A.J., Farmer, B.D., Ledbetter, C.K. 2013. Safety of feed treated with 17a- methyltestosterone (17MT) to larval Nile tilapia. North American Journal of Aquaculture. 75:212-219.
- Li, C., Beck, B.H., Su, B., Terhune, J., Peatman, E. 2013. Early mucosal responses in blue catfish (Ictalurus furcatus) skin to Aeromonas hydrophila infection. Fish and Shellfish Immunology. 34(3):920-928.
- Farmer, B.D., Beck, B.H., Mitchell, A.J., Straus, D.L. 2013. Pretreating channel catfish with copper sulfate affects susceptibility to columnaris. North American Journal of Aquaculture. 75(2):205-211.
- Farmer, B.D., Straus, D.L., Beck, B.H., Mitchell, A.J., Freeman, D.W., Meinelt, T. 2013. Effectiveness of copper sulfate, potassium permanganate, and peracetic acid to reduce mortality and infestation of Ichthyobodo nector in channel catfish Ictalurus punctatus (Rafinesque 1818). Aquaculture Research. 44(7):1103-1109.
- Li, C., Wang, R., Su, B., Luo, Y., Terhune, J., Beck, B.H., Peatman, E. 2013. Evasion of mucosal defenses during Aeromonas hydrophila infection of channel catfish (Ictalurus punctatus) skin. Developmental and Comparative Immunology. 39(4):447-455.
- Beck, B.H., Farmer, B.D., Straus, D.L., Li, C., Peatman, E. 2012. Rhamnose- binding lectins and their ligands: Putative roles in Flavobacterium columnare pathogenesis in channel catfish Ictalurus punctatus. Fish and Shellfish Immunology. 33(4):1008-1015.
- Marchand, P., Straus, D.L., Weinke, A., Pedersen, L., Meinelt, T. 2013. Effect of water hardness on peracetic toxicity to zebrafish, Danio rerio, embryos. Aquaculture International. 21(3):679-686.
- Peatman, E., Li, C., Peterson, B.C., Straus, D.L., Farmer, B.D., Beck, B.H. 2013. Basal polarization of the mucosal compartment in Flavobacterium columnare susceptible and resistant channel catfish Ictalurus punctatus. Molecular Immunology. 56(4):317-327.
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Progress 10/01/11 to 09/30/12
Outputs
Progress Report Objectives (from AD-416): The long-term objective of this project is to characterize the pathogenesis of fish diseases and to develop approaches to control diseases in warm water fishes. Over the next 5 years, our project at the Stuttgart National Aquaculture Research Center (SNARC) will focus on the following objectives: Objective 1. Characterize genetic variation of white bass and sunshine bass resistance to columnaris and develop strategies to control columnaris in warm water aquaculture. Subobjective 1A. Develop a Flavobacterium columnare disease model in white bass (Morone chrysops) and sunshine bass (female Morone chrysops x male M. saxitalis). Determine whether there is genetic variation for survival of white bass and sunshine bass in response to columnaris infection (Darwish and Mitchell). Subobjective 1B. Characterize Flavobacterium columnare virulence genes using real-time PCR to evaluate gene expression (Straus). Objective 2. Evaluate compounds and methods to treat bacterial and fungal (columnaris, streptococcosis, and saprolegniasis) fish diseases. Subobjective 2A. Control columnaris in channel catfish with copper sulfate (Darwish, Mitchell, and Straus). Subobjective 2B. Control saprolegniasis on channel catfish eggs and improving hatch rate by chemical means (Mitchell and Straus). Subobjective 2C. Evaluate caprylic acid to control streptococcosis in sunshine bass (Darwish). These objectives are designed to address current research concerns of stakeholders and will help in the ultimate goal of better treatments for disease epizootics resulting in higher profits for producers. Approach (from AD-416): Objective 1. An infection method will be developed for white bass and sunshine bass to produce consistent mortalities similar to a natural infection of the bacterial disease columnaris caused by F. columnare. Resistance to columnaris will be characterized in families of sunshine bass and white bass, and maternal and paternal effects will be determined. The expression level of the putative virulence genes (identified by sequence comparison) in F. columnare will be characterized to provide insight into bacterial pathogenesis. Reverse-transcriptase real-time PCR methods will be developed and used to profile the transcript level of selected genes in isolates of high and low pathogenicity. Objective 2. The efficacy of CuSO4 against columnaris will be tested in vitro using micro-dilution assays and in vivo by using four treatment levels of CuSO4 against a columnaris disease model simulating a natural infection. The scenarios used to expose channel catfish to CuSO4 prior to bacterial challenge based on previous work will consist of either pre- exposure to CuSO4 dissolved in the water or pre-exposure to CuSO4 incorporated in feed. Research will be designed to improve the effectiveness of CuSO4, H2O2, and formalin to fungi on channel catfish eggs and on the hatch rate of these eggs. A new aquaculture therapeutant (peracetic acid) will be used to treat saprolegniasis on intact channel catfish eggs in hatching troughs. The concentration of caprylic acid that inhibits the bacteria S. iniae will be determined in vitro and its potential efficacy will be assessed against an experimental S. iniae infection in sunshine bass. We continued using molecular methods (i.e., real-time quantitative PCR) to measure virulence gene expression in cultured Flavobacterium columnare strains and will compare this expression to samples from diseased fish; this test will predict which strain(s) of bacteria will cause the most severe disease. We initiated acute toxicity tests on juveniles of several species to develop a more complete understanding on the use of peracetic acid in aquaculture. We evaluated Flavobacterium columnare concentrations and fish densities required to produce consistent columnaris infections in white bass and in hybrid striped bass. We found that white bass genetically selected for growth are less susceptible to F. columnare than hybrid striped bass. We used molecular methods to study the mechanisms of columnaris disease. We also examined the role of nutritional status on RBL regulation. We conducted experiments to evaluate the effects of pre-exposure of channel catfish fingerlings to copper sulfate on susceptibility to columnaris disease. Results indicate that resistance can be induced but is strongly correlated to the time between copper sulfate exposure and bacterial challenge. We compared the potential of copper sulfate and peracetic acid treatments to prevent fungus on hybrid striped bass eggs. Preliminary data suggests that copper sulfate is more effective than peracetic acid and results in higher survival of fry through the hatching stage (Subordinate project 6225-32000-005-09N). We prepared final study reports for completed effectiveness dose confirmation studies on using copper sulfate to control egg mortality associated with saprolegniasis infecting channel catfish eggs and are submitting these to the sponsor who will submit them to FDA (Subordinate project 6225-32000-005-07N). Accomplishments 01 Pre-exposure to copper can protect fish from columnaris disease. Columnaris is a major fish bacterial disease causing significant losses the aquaculture industry. ARS researchers at the Stuttgart National Aquaculture Center in Stuttgart, Arkansas, demonstrated that challenging fish with columnaris bacteria immediately after a 24-hour copper sulfate exposure produced significantly lower survival than fish that were allow an additional 24 hours in flow-through water before bacterial challenge; resistance was determined to last at least 9 days after the copper sulfa exposure. This research can be used by producers to develop best management practices for implementation when risk of disease is greatest (e.g., seining ponds, grading fingerlings, hauling fish to grow-out facilities), since available treatments for columnaris are limited. As there is a trend towards reducing expensive antibiotic treatments, havin a proven, economical treatment like copper sulfate benefits the US aquaculture industry. More widespread adoption of this technology is expected in the next few years. 02 Bacterial binding sites can be altered to control columnaris disease. Columnaris is a major fish bacterial disease causing significant losses the aquaculture industry. Evidence suggests a part of the fish immune system that assists in killing bacteria, called rhamnose-binding lectins are increased in the gill of catfish infected with columnaris and can be measured using molecular tools. Using these tools, ARS scientists in Stuttgart, Arkansas, demonstrated dramatic evidence of increased immunit to columnaris after exposing fish to the bacteria and examining the quantity of lectins in the gills of two different families of channel catfish, and determined that one family was susceptible to the disease, while the other was completely resistant. The quantity of lectins in th gill was strongly increased in the columnaris-susceptible family, but by reducing the number of lectin binding sites on the gill, the catfish cou be protected from columnaris disease. The nutritional status of the fish also had an effect, with a far greater amount of lectins in the gill of unfed fish relative to well-fed fish. Application of these findings to develop screening techniques for enhanced resistance to columnaris would substantially reduce losses of farm-raised catfish and increase industry profitability, while potential future application to other farm-raised fish species would benefit additional U.S. aquaculture producers and consumers.
Impacts
(N/A)
Publications
- Straus, D.L., Mitchell, A.J., Carter, R.R., Steeby, J.A. 2011. Dose- confirmation of copper sulfate for treating fungus on channel catfish eggs at a commercial hatchery. Journal of Applied Aquaculture. 23(3):199-206.
- Straus, D.L., Mitchell, A.J., Carter, R.R., Mcentire, M.E., Steeby, J.A. 2012. Safety of copper sulfate to channel catfish eggs. North American Journal of Aquaculture. 74:60-64.
- Darwish, A.M., Mitchell, A.J., Straus, D.L. 2012. Evaluation of a 4-h static copper sulphate treatment against experimental infection of Flavobacterium columnare in channel catfish (Ictalurus punctatus). Journal of Fish Diseases. 43:688-695.
- Farmer, B.D., Mitchell, A.J., Straus, D.L. 2011. The effect of high total ammonia concentration on the survival of channel catfish experimentally infected with Flavobacterium columnare. Journal of Aquatic Animal Health. 23:162-168.
- Straus, D.L., Bowker, J.D., Bowman, M.P., Carty, D., Mitchell, A.J., Farmer, B.D. 2012. Safety of Aquaflor(c)-medicated feed to sunshine bass. North American Journal of Aquaculture. 74:1-7.
- Straus, D.L., Mitchell, A.J., Carter, R.R., Steeby, J.A. 2011. Hatch rate of channel catfish Ictalurus punctatus (Rafinesque 1818) eggs treated with 100 mg L-1 copper sulphate pentahydrate. Aquaculture Research. 43:14-18.
- Straus, D.L., Meinelt, T., Farmer, B.D., Beck, B.H. 2012. Acute toxicity and histopathology of channel catfish fry exposed to peracetic acid. Aquaculture. 342-343(1):134-138.
- Straus, D.L., Meinelt, T., Farmer, B.D., Mitchell, A.J. 2012. Peracetic acid is effective for controlling fungus on channel catfish eggs. Journal of Fish Diseases. 35:505-511.
- Farmer, B.D., Beck, B.H., Straus, D.L. 2012. Effectiveness of copper sulfate and potassium permanganate on channel catfish infected with Flavobacterium columnare. North American Journal of Aquaculture. 74(3):320- 329.
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Progress 10/01/10 to 09/30/11
Outputs
Progress Report Objectives (from AD-416) The long-term objective of this project is to characterize the pathogenesis of fish diseases and to develop approaches to control diseases in warm water fishes. Over the next 5 years, our project at the Stuttgart National Aquaculture Research Center (SNARC) will focus on the following objectives: Objective 1. Characterize genetic variation of white bass and sunshine bass resistance to columnaris and develop strategies to control columnaris in warm water aquaculture. Subobjective 1A. Develop a Flavobacterium columnare disease model in white bass (Morone chrysops) and sunshine bass (female Morone chrysops x male M. saxitalis). Determine whether there is genetic variation for survival of white bass and sunshine bass in response to columnaris infection (Darwish and Mitchell). Subobjective 1B. Characterize Flavobacterium columnare virulence genes using real-time PCR to evaluate gene expression (Straus). Objective 2. Evaluate compounds and methods to treat bacterial and fungal (columnaris, streptococcosis, and saprolegniasis) fish diseases. Subobjective 2A. Control columnaris in channel catfish with copper sulfate (Darwish, Mitchell, and Straus). Subobjective 2B. Control saprolegniasis on channel catfish eggs and improving hatch rate by chemical means (Mitchell and Straus). Subobjective 2C. Evaluate caprylic acid to control streptococcosis in sunshine bass (Darwish). These objectives are designed to address current research concerns of stakeholders and will help in the ultimate goal of better treatments for disease epizootics resulting in higher profits for producers. Approach (from AD-416) Objective 1. An infection method will be developed for white bass and sunshine bass to produce consistent mortalities similar to a natural infection of the bacterial disease columnaris caused by F. columnare. Resistance to columnaris will be characterized in families of sunshine bass and white bass, and maternal and paternal effects will be determined. The expression level of the putative virulence genes (identified by sequence comparison) in F. columnare will be characterized to provide insight into bacterial pathogenesis. Reverse-transcriptase real-time PCR methods will be developed and used to profile the transcript level of selected genes in isolates of high and low pathogenicity. Objective 2. The efficacy of CuSO4 against columnaris will be tested in vitro using micro-dilution assays and in vivo by using four treatment levels of CuSO4 against a columnaris disease model simulating a natural infection. The scenarios used to expose channel catfish to CuSO4 prior to bacterial challenge based on previous work will consist of either pre- exposure to CuSO4 dissolved in the water or pre-exposure to CuSO4 incorporated in feed. Research will be designed to improve the effectiveness of CuSO4, H2O2, and formalin to fungi on channel catfish eggs and on the hatch rate of these eggs. A new aquaculture therapeutant (peracetic acid) will be used to treat saprolegniasis on intact channel catfish eggs in hatching troughs. The concentration of caprylic acid that inhibits the bacteria S. iniae will be determined in vitro and its potential efficacy will be assessed against an experimental S. iniae infection in sunshine bass. We compared the potential of static and flow-through peracetic acid (PAA) treatments to increase channel catfish egg survival and prevent fungal growth on eggs in a hatchery setting; static treatments required the lowest concentration of PAA, but turning water off in hatcheries would not be a practical application. We determined the acute toxicity of PAA to channel catfish fry; PAA was safer to use on newly hatched fry than on fry that were about 9 days old, but there was very low toxicity. We collaborated on a study to develop data on the use of PAA to reduce the growth rates of Flavobacterium columnare and Saprolegnia parasitica in culture. (Subordinate project 6225-32000-005-04N). We used the previously developed low-flow water delivery system to study the disease progression of columnaris in sunshine bass to produce consistent infections in order to study immune response characteristics; samples were taken to understand the molecular mechanisms of the disease and to observe any cellular changes. We determined that copper sulfate was more effective than potassium permanganate in lowering fish mortality in catfish naturally infected with columnaris, contrary to the generally accepted view that potassium permanganate is the best treatment. The efficacy of Aquaflor (c), copper sulfate, and potassium permanganate in controlling infections of Aeromonas hydrophila and F. columnare in sunshine bass was evaluated; Aquaflor (c) and copper sulfate were demonstrated to increase survival. We determined the length of time a parasite (Bolbophorus damnificus) can persist in channel catfish; this study outlined the potential severity of an infection. We collaborated on a study to determine the bioaccumulation of copper in red drum tissues after prescribed treatments to control external parasites (e.g., Amyloodinium sp.); this study went further to define the withdrawal period so the fish can be safely returned to the food supply. We used molecular methods (i.e., real-time PCR) to measure virulence gene expression in cultured Flavobacterium columnare strains and will compare this expression to samples from diseased fish; this test will predict which strain of the bacteria will cause the most severe disease. Accomplishments 01 Copper sulfate beats potassium permanganate in treating columnaris in channel catfish. Columnaris is known to be a severe bacterial disease i catfish culture. Treatment with approved antibiotics (such as potassium permanganate) is costly and can promote bacterial resistance. ARS scientists at the Stuttgart National Aquaculture Research Center, Stuttgart, AR, used fish with a natural infection of columnaris to evaluate the effectiveness of copper sulfate and potassium permanganate. The copper sulfate treatment was superior and significantly reduced mortalities. Since available resources to treat columnaris are limited, having a proven, economical treatment like copper sulfate will benefit t US aquaculture industry. 02 Immune response during simulated disease progression of columnaris in sunshine bass. Columnaris is one of the most lethal bacterial diseases farmed fish. In an effort to identify factors that confer resistance to the disease, ARS scientists at the Stuttgart National Aquaculture Resear Center, Stuttgart, AR, conducted a study to examine how the sunshine bas immune system responds to a laboratory-induced infection. Using differe doses, researchers determined the optimum concentration of bacteria that reliably produced columnaris disease. Fish surviving the infection had more white blood cells in certain immune tissues than uninfected fish. White blood cells isolated from survivors responded more vigorously than those from fish that were not exposed to the bacteria. These findings a being used to develop screening techniques to predict whether certain fi may be more resistant to columnaris disease, which would ultimately improve profit margins for sunshine bass producers. 03 Longevity of Bolbophorus damnificus infections in channel catfish. The worm-like parasite Bolbophorus damnificus has a complex life cycle and infects commercial catfish, causing mortality, lower feed consumption, a reduced growth in surviving fish. In a collaborative study with scientists at Mississippi State University and ARS, scientists at the Stuttgart National Aquaculture Research Center, Stuttgart, AR, determine the length of time it remains viable in catfish. Our results indicate that the parasite can survive during the standard 18 to 30 month production cycle in the catfish industry. Live parasites impact catfis growth, and infected fish can serve as intermediate hosts for these parasites for at least 2.5 years. This study demonstrates to the catfis industry how important it is to use treatments to prevent the introducti of this parasite into the pond. 04 Peracetic acid has low toxicity to channel catfish fry. For peracetic acid (PAA) to be used to treat fungus on catfish eggs, its toxicity to hatching fry needed to be demonstrated. A collaborative study with a scientist at the Leibniz-Institute of Freshwater Ecology and Inland Fisheries, Berlin, Germany, and ARS scientists at the Stuttgart National Aquaculture Research Center, Stuttgart, AR, determined that PAA was safe to use on newly hatched fry than on fry that were about 9 days old, but there was very low toxicity. This research demonstrates the safety and usefulness of this novel compound and may result in widespread use. 05 Small amounts of peracetic acid reduce growth in aquatic pathogen cultur Commercial products containing peracetic acid (PAA) are strong disinfectants with a wide spectrum of antimicrobial activity. A collaborative study with the Leibniz-Institute of Freshwater Ecology and Inland Fisheries, Berlin, Germany, the Universit� Catholique de Louvain, Louvain-la-Neuve, Belgium, and the Stuttgart National Aquaculture Resear Center, Stuttgart, AR, compared the in vitro reduction of growth of Flavobacterium columnare and Saprolegnia parasitica using seven commerci PAA-containing products. Results showed that the products with a low concentration of PAA and a low PAA: hydrogen peroxide-ratio were general more effective against pathogens. This research provides data for a new use of a widely used disinfectant that may also be useful in U.S. and international aquaculture. 06 Bioaccumulation of copper in red drum tissues after treatment. Red drum are cultured for food fish, and copper is routinely used to control external parasites. In a collaborative study, scientists at the Harbor Branch Oceanographic Institute of Florida Atlantic University, Fort Pier FL, and ARS scientists at the Stuttgart National Aquaculture Research Center, Stuttgart, AR, suspected that it tends to accumulate in the tiss of the fish. Healthy red drum were exposed to a chelated copper product for 8 months to control external parasites. Various tissues were analyz for copper content, and we found that liver and intestine accumulated a high amount, while skin, gill, and muscle tissue did not accumulate substantial amounts. We also found that red drum cultured in recirculating systems had lower copper concentrations in muscle tissue relative to wild-caught red drum. Data indicates a 21-day withdrawal period is sufficient to meet the standards for human consumption. This research will significantly benefit the safety of the U.S. food supply while helping fish-farmers maintain a healthy fish population. 07 Treating common bacterial diseases in sunshine bass with Aquaflor (R), copper sulfate and potassium permanganate. Sunshine bass operations in the US have been plagued by pathogens like Aeromonas hydrophila and Flavobacterium columnare. This was a collaborative study with ARS scientists at the Aquatic Animal Health Research Laboratory, Auburn, AL, the Thad Cochran Research Center,University, MS, and the Stuttgart National Aquaculture Research Center, Stuttgart, AR. Aquaflor (R) - medicated feed (active ingredient is the antibiotic florfenicol) was sho to significantly increase the survival of sunshine bass infected with these bacteria better than copper sulfate and potassium permanganate. These results furnish the industry with potentially beneficial treatment against common infections.
Impacts
(N/A)
Publications
- Bowker, J., Trushenski, J., Tuttle-Lau, M., Straus, D.L., Gaikowski, M., Goodwin, A., Sprague, L., Bowman, M. 2011. Guide to Using Drugs, Biologics, and Other Chemicals in Aquaculture. American Fisheries Society Book Series. Available:
- Ogunsanya, T., Durborow, R.M., Webster, C.D., Tidwell, J.H., Thompson, K., Coyle, S., Jarboe, H.H., Huang, L., Straus, D.L., Wang, C. 2011. Toxicity of rotenone to giant river freshwater prawn Macrobrachium rosenbergii. North American Journal of Aquaculture. 73:159-163.
- Darwish, A.M., Mitchell, A.J., Straus, D.L. 2010. Evaluation of the therapeutic effect of potassium permanganate at early stages of an experimental acute infection of Flavobacterium columnare in channel catfish (Ictalurus punctatus). Aquaculture Research. 41(10):1479-1485.
- Mitchell, A.J., Yost, M., Panuska, C., Farmer, B.D., Pote, L. 2011. Longevity of Bolbophorus damnificus infections in channel catfish. Journal of Aquatic Animal Health. 23(2):103-109.
- Darwish, A.M. 2010. Effectiveness of early intervention with florfenicol on a Streptococcus iniae infection in blue tilapia. North American Journal of Aquaculture. 72(4):354-360.
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Progress 10/01/09 to 09/30/10
Outputs
Progress Report Objectives (from AD-416) The long-term objective of this project is to characterize the pathogenesis of fish diseases and to develop approaches to control diseases in warm water fishes. Over the next 5 years, our project at the Stuttgart National Aquaculture Research Center (SNARC) will focus on the following objectives: Objective 1. Characterize genetic variation of white bass and sunshine bass resistance to columnaris and develop strategies to control columnaris in warm water aquaculture. Subobjective 1A. Develop a Flavobacterium columnare disease model in white bass (Morone chrysops) and sunshine bass (female Morone chrysops x male M. saxitalis). Determine whether there is genetic variation for survival of white bass and sunshine bass in response to columnaris infection (Darwish and Mitchell). Subobjective 1B. Characterize Flavobacterium columnare virulence genes using real-time PCR to evaluate gene expression (Straus). Objective 2. Evaluate compounds and methods to treat bacterial and fungal (columnaris, streptococcosis, and saprolegniasis) fish diseases. Subobjective 2A. Control columnaris in channel catfish with copper sulfate (Darwish, Mitchell, and Straus). Subobjective 2B. Control saprolegniasis on channel catfish eggs and improving hatch rate by chemical means (Mitchell and Straus). Subobjective 2C. Evaluate caprylic acid to control streptococcosis in sunshine bass (Darwish). These objectives are designed to address current research concerns of stakeholders and will help in the ultimate goal of better treatments for disease epizootics resulting in higher profits for producers. Approach (from AD-416) Objective 1. An infection method will be developed for white bass and sunshine bass to produce consistent mortalities similar to a natural infection of the bacterial disease columnaris caused by F. columnare. Resistance to columnaris will be characterized in families of sunshine bass and white bass, and maternal and paternal effects will be determined. The expression level of the putative virulence genes (identified by sequence comparison) in F. columnare will be characterized to provide insight into bacterial pathogenesis. Reverse-transcriptase real-time PCR methods will be developed and used to profile the transcript level of selected genes in isolates of high and low pathogenicity. Objective 2. The efficacy of CuSO4 against columnaris will be tested in vitro using micro-dilution assays and in vivo by using four treatment levels of CuSO4 against a columnaris disease model simulating a natural infection. The scenarios used to expose channel catfish to CuSO4 prior to bacterial challenge based on previous work will consist of either pre- exposure to CuSO4 dissolved in the water or pre-exposure to CuSO4 incorporated in feed. Research will be designed to improve the effectiveness of CuSO4, H2O2, and formalin to fungi on channel catfish eggs and on the hatch rate of these eggs. A new aquaculture therapeutant (peracetic acid) will be used to treat saprolegniasis on intact channel catfish eggs in hatching troughs. The concentration of caprylic acid that inhibits the bacteria S. iniae will be determined in vitro and its potential efficacy will be assessed against an experimental S. iniae infection in sunshine bass. Compared the potential of static and flow-through hydrogen peroxide and copper sulfate treatments to increase channel catfish egg survival and prevent fungal growth on eggs; hydrogen peroxide static treatments proved best. Completed the development of a low-flow water delivery system for columnaris challenge testing. High levels of ammonia in water were shown to lower fish mortality in fish infected with bacteria, contrary to the generally accepted view that ammonia increases mortality in infected fish. Investigated the therapeutic value of copper sulfate against an acute columnaris infection in channel catfish; fish challenged with Flavobacterium columnare and treated by waterborne exposure to copper sulfate (4.2 and 2.1 mg/L) had reduced mortalities compared to non- treated fish. Evaluated the efficacy of florfenicol, copper sulfate and potassium permanganate in controlling infections of Aeromonas hydrophila and F. columnare in sunshine bass; florfenicol and copper sulfate were demonstrated to increase the survival rate. The microbiology laboratory participated by invitation in an international multi-laboratory study to establish the expected drug sensitivity ranges of the quality control bacteria, Escherichia coli (ATCC25922) and Aeromonas salmonicida (ATCC33658). Designed a primer set and fluorescent probe to amplify the 16S ribosomal gene of F. columnare to be used as an internal control for virulence gene expression. Completed the in-life phase of a safety study to demonstrate that the proposed recommended daily treatment of 17a-methyltestosterone (9 mg/kg fish body weight) and 3 or 5 times the recommended treatment for 28 days were safe for treating tilapia. Evaluated peracetic acid, copper sulfate, and potassium permanganate to control Ichthyobodo necator; copper sulfate was the best treatment. Completed testing on acute toxicity of CuSO4 to Ich theronts in reconstituted waters (Subordinate project 6225-32000-005-03N). Evaluated peracetic acid for fungus control on catfish egg masses in a flow-through system; 2.5 mg/L twice a day prevented fungus from growing and destroying the eggs (Subordinate project 6225-32000-005-04N). Accomplishments 01 FDA-required study on the safety of 17A-methyltestosterone (17MT) to tilapia. The histological safety of 17MT, used to produce an all-male population, is unknown, but is required as a major component of the FDA- approval process. A study was completed in collaboration with researcher at the US Fish & Wildlife Service in Bozeman, Montana, to demonstrate th the proposed recommended daily treatment (9 mg/kg fish body weight) and or 5 times the recommended treatment for 28 days were safe for treating tilapia. Mortality data indicates an acceptable margin of safety. Approv will benefit the US tilapia industry by allowing farmers to use 17MT legally in tilapia hatcheries. 02 Peracetic acid (PAA) controls fungus on catfish eggs. Fungus in catfish hatcheries can cause decreased hatch rates. A collaborative study with a scientist at the Leibniz-Institute of Freshwater Ecology and Inland Fisheries (Berlin, Germany) and scientists at the HKD Stuttgart National Aquaculture Research Center addresses egg mortality from fungus in catfi hatcheries. This range-finding study determined that treating catfish eg twice daily with 2.5 ppm PAA until hatching begins will prevent fungus from growing and destroying the eggs. This accomplishment will provide direct benefits through increased survival rates in catfish hatcheries, which will economically benefit the industry. In addition, we have provided the scientific community with more information on the uses of this novel compound. 03 FDA-Required study on copper sulfate safety to catfish eggs accepted by FDA. The safety of copper sulfate to catfish eggs was unknown. A repor entitled 'A Target Animal Safety Study on the use of Copper Sulfate to Control Egg Mortality Associated with Saprolegniasis Infecting Channel Catfish Eggs' was submitted to the FDA in December 2009 and accepted in May 2010. This study was completed following Good Laboratory Practice guidelines and determined the safety of this compound to channel catfish eggs at 10, 30, and 50 mg/L when treated daily until embryos developed eyes. Hatch rate was not affected by copper toxicity, indicating this is an extremely safe treatment. This work completed a major component of th approval process, thereby improving the economics of the industry by providing an inexpensive treatment to increase survival rates in catfish hatcheries. 04 High levels of ammonia reduce mortality in channel catfish infected with columnaris. The interaction of ammonia and Flavobacterium columnare is poorly understood; however, it is generally accepted that elevated ammon levels increase mortalities of diseased fish. A concentration of 15 ppm ammonia significantly increased survival of fish exposed to columnaris. Knowledge of this interaction will lead to a better understanding of the mechanisms involved in treating diseases. The use of high ammonia levels in fish tanks could produce an effective treatment for columnaris, which is one of the two most costly diseases to the channel catfish industry. 05 Hydrogen peroxide static treatments effective for fungus control on catfish eggs. Water molds or fungi can destroy entire channel catfish e masses in commercial hatching troughs, costing fish producers several hundred thousands of dollars of losses and fish shortages. An experiment was designed to compare static and flow-through hydrogen peroxide and copper sulfate pentahydrate treatments for their ability to control fung and increase egg survival. All treatments were observed to limit egg fungus and increase egg survival, but the highest egg survival and least fungal development were achieved using a static hydrogen peroxide treatment. The use of a static hydrogen peroxide treatment on fish eggs will potentially allow hatcheries to produce more juvenile channel catfi and realize greater economic benefits. 06 Copper sulfate is effective against acude columnaris infections in chann catfish. Approved antibiotics are costly and can promote bacterial resistance when treating columnaris. Copper sulfate was evaluated as a therapeutant against acute columnaris in channel catfish and significant reduced the mortalities. The available resources to treat columnaris are limited, and having an economical treatment like copper sulfate will benefit the US aquaculture industry. 07 Florfenicol, copper sulfate, and potassium permanganate efficacy against natural infection of Aeromonas hydrophila and Flavobacterium columnare i sunshine bass. Sunshine bass operations in the US have been plagued by pathogens like Aeromonas hydrophila and Flavobacterium columnare. Florfenicol medicated feed was shown to significantly increase the survival of sunshine bass infected with these bacteria. These results furnish the industry with potentially beneficial treatments against thes common infections.
Impacts
(N/A)
Publications
- Mitchell, A.J., Straus, D.L., Farmer, B.D., Carter, R.R. 2010. Comparison of percent hatch and fungal infestation in channel catfish eggs after copper sulfate, diquat bromide, formalin, and hydrogen peroxide treatment. North American Journal of Aquaculture. 72:201-206.
- Mitchell, A.J., Farmer, B.D. 2010. Evaluation of an ultra low-flow water delivery system for small experimental tanks. North American Journal of Aquaculture. 75:195-200.
- Meinelt, T., Matzke, S., Stuber, A., Pietrock, M., Wienke, A., Mitchell, A. J., Straus, D.L. 2009. Toxicity of peracetic acid (PAA) to tomonts of Ichthyophthirius multifiliis. Diseases of Aquatic Organisms. 86(1):51-56.
- Sudova, E., Straus, D.L., Wienke, A., Meinelt, T. 2010. Evaluation of continuous 4 day exposure to peracetic acid as a treatment for Ichthyophthirius multifiliis. Parasitology Research. 106:539-542.
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