2003 Annual Report 1.What major problem or issue is being resolved and how are you resolving it? Question 1: Losses from disease threaten the continued success of the commercial catfish industry. The overall goal of the fish health project is to provide disease diagnostics and surveillance for new and emerging diseases and to develop management strategies that optimize fish health and minimize the impact of disease related losses. Specific areas of research have been identified through interactions with industry advisory groups, extension service representatives and research personnel in other disciplines, agencies, and institutions. The program focuses on developing and evaluating new rapid diagnostic technologies, establishing early disease detection methodologies and disease monitoring programs, identifying risk factors that influence the onset and severity of disease outbreaks, evaluating disease treatment strategies, establishing best management practices to prevent and manage disease outbreaks with minimal economic loss to producers, developing disease challenge models to evaluate the pathogenesis and treatment of infectious diseases, and providing an outlet by which information generated by diagnostic and research efforts are transferred to producers. 2.How serious is the problem? Why does it matter? Question 2: The Mississippi catfish industry encompasses approximately 400 farms and 111,000 water surface acres, that produced 381 million pounds of food size fish, valued at $240 million in 2001. The industry employs more than 3000 workers on catfish farms, 3,600 in processing plants, and 330 in feed mills, with a total payroll exceeding $102 million. When related service industries are taken into account, channel catfish production contributed more than $2 billion to Mississippi's economy. Viability of the industry is threatened by multiple factors, including competition with foreign imports, rising production costs, and losses from disease. Since the inception of the catfish industry, 40 years ago, disease related losses have represented a major impediment to the profitability of the enterprise. In the last decade, problems have escalated as culture practices have become more intensive and previously rare diseases have been amplified among the closely confined populations of cultured fish. It is estimated that disease related losses account for approximately 45-50% of all losses incurred on farms annually and may account for as much as $100 million annually in direct economic losses. Examination of case records from the Thad Cochran National Warmwater Aquaculture Center-Aquatic Diagnostic Laboratory indicate that over the past six years, the bacterial diseases enteric septicemia of catfish (ESC) and columnaris disease have on average accounted for 37.6% and 44.0% of all diagnostic submissions, respectfully. Proliferative gill disease (PGD) accounts for 23.5% of diagnoses, saprolegniosis (winter fungus) 9.1%, channel catfish virus disease (CCVD) 3.9%, channel catfish anemia (CCA) 3.8%, Bolbophorus damnificus trematodes 3.8%, visceral toxicosis of catfish (VTC) 2.3%, and Ichthyophthirius multifiliis (Ich) 1.4%. In general, progress in the area of disease control is limited by a poor understanding of the pathogenesis of the major disease entities, inadequate knowledge of the relationships between management practices and other risk factors associated with disease outbreaks, and a lack of disease challenge models duplicating typical field conditions. In other instances, promising disease control measures do not fit economically or practically into typical production schemes currently in use. Lastly, there is a paucity of chemical agents, antibiotics, and vaccines approved for treatment or preventative uses. A comprehensive fish health research program focusing on production efficiency and disease management is needed to address fish health issues and ensure the economic viability of the channel catfish industry. 3.How does it relate to the National Program(s) and National Program Component(s) to which it has been assigned? Question 3: The USDA Agricultural Research Service (ARS) national research program is divided into three main areas:. 1)animal production, product value, and safety,. 2)natural resources and sustainable agricultural systems, and. 3)crop production, product value, and safety. Research objectives for the Catfish Genetics Research Unit fall under the animal production, product value, and safety area. The main goal of this research area is to enhance the production, value, and safety of foods and other products derived from animals which have a major impact on the American economy, world markets, and the U.S. balance of trade. Research in the Catfish Genetics Research Unit is in the aquaculture national program area (NP106) within animal production, product value, and safety. Aquaculture research for the USDA/ARS focuses on a rapidly growing agricultural segment of the U.S. economy. With increasing seafood demand, declining capture fisheries, and a fisheries trade deficit exceeding $4 billion annually, aquaculture is poised to become a major U.S. growth industry in the 21st century. The continued growth and competitiveness of U.S. aquaculture will be directly related to the resources invested in research and technology development. A strong research and technology development program for U.S. aquaculture, led by the Agricultural Research Service, will offer significant benefits to both producers and consumers by enhancing the production efficiency, profitability, and quality of aquaculture products and systems. Research approaches for the Catfish Genetics Research Unit generally fall within three areas defined by the USDA/ARS Aquaculture National Program 106:. 1)genetic improvement;. 2)reproduction and early development; and. 3)growth, development and nutrition. 4.What were the most significant accomplishments this past year? Question 4: A. Single Most Significant Accomplishment during FY 2003 Research was conducted to evaluate the effect of sublethal Bolbophorus sp. infection on the resistance of channel catfish to bacterial infections, to determine possible causes of unexplained mortalities associated with natural trematode infections. This data indicates that parasitism with this trematode decreases resistance to bacterial infection, probably as a complication of penetration of the parasite or initial stages of metacercarial encystment. Presence of the mature parasite alone does not appear to compromise performance of the fish, indicating this disease can be effectively controlled by breaking the life cycle of the organism. B. Other Significant Accomplishment(s) Visceral toxicosis of catfish (VTC) is the name applied to a syndrome of unexplained catastrophic mortality events that have occurred sporadically on catfish farms in the Mississippi Delta since 1998. National Warmwater Aquaculture Center personnel investigated outbreaks on 14 farms in FY 2002, documented lesions, performed bioassay procedures, and collected serum samples that have been forwarded to collaborators at the Mississippi State Chemistry Laboratory. Analytical techniques, unavailable at the NWAC, are being applied to isolate the toxic component. Bioassay testing continues at the NWAC on serum fractions that will ultimately lead to characterization and identification of the toxin. Channel catfish anemia (CCA) is a well-known, but poorly understood cause of mortalities in market size catfish, characterized by severe anemia. A review of the literature indicated that the anemia had not been fully characterized, so classical clinical pathologic and histopathologic techniques have been applied to the study of hematopoietic tissues and blood films. Preliminary findings suggest the anemia may result from an interruption of the normal maturation sequence of red blood cell precursors. Although, further studies are needed, complete characterization of the anemia may suggest possible causes for this enigmatic condition. Bacterial diseases, particularly enteric septicemia (ESC) caused by Edwardsiella ictaluri, represent a major impediment to the profitability of commercial catfish farming and currently only two antibiotics are approved for use in this species. Florfenicol (Aquaflor®), an antibiotic approved for use in fish in Europe, Canada, Japan and South America, but not in the United States, was tested in aquarium and pond studies conducted at the National Warmwater Aquaculture Center for effectiveness against E. ictaluri infections in channel catfish. During FY 2002, the results of these trials were submitted to the U.S. Food and Drug Administration, which has accepted efficacy, safety, residue, and environmental impact studies. Approval of the drug for use in catfish will provide farmers with a potent new drug for combating the most significant bacterial disease facing the industry. Diagnostic laboratories provide an essential service to all forms of animal agriculture, including aquaculture. The Aquatic Diagnostic Laboratory, Thad Cochran National Warmwater Aquaculture Center in Stoneville, Mississippi, provides catfish farmers with a comprehensive disease diagnostic service, as well as a mechanism for surveillance of changing disease trends and new and emerging disease problems. In 2002, the Laboratory processed 1057 diagnostic cases, 249 research cases, and 1191 water samples. The diagnostic information supplied to farmers allows them to make educated decisions regarding the treatment of diseases that threaten the economic performance of their operations. A trematode parasite, indentified as Bolbophorus sp., has rapidly become one of the most economically damaging diseases affecting the farm-raised catfish industry where severe infections can cause complete losses of fingerling catfish and significant production losses of food-size fish. Research was conducted to investigate the epidemiology of this disease, to determine the prevalence and severity of the disease throughout the industry, and establish research priorities. The data indicates that infections with this trematode are widespread in all counties producing channel catfish in Northwestern Mississippi and established risk factors associated with the development of the disease. This information was instrumental in developing management strategies for limiting the impact of this disease, generated scientific and technical publications, and provided the basis for research grants and cooperative research projects with other institutions. To address production losses associated with a trematode infection identified as Bolbophorus sp., research was conducted to evaluate methods of controlling snail populations, the intermediate host of the parasite. Laboratory and field trials demonstrated that hydrated lime was effective in reducing snail populations around the margins of pond banks. Recommendations resulting from this work have lead to treatments that can effectively control trematode infections and prevent condemnation of commercial catfish ponds containing infected fish. Research was conducted to evaluate the effects of water temperature on emergence of Bolbophorus sp. cercariae from infected ram's horn snails, Planorbella trivolvis, to develop strategies of controlling infections in commercially raised channel catfish. Data demonstrated that although infected snails do not shed cercariae at temperatures below 15 C, they retain viable sporocyts, resulting in the emergence of additional cercariae when snails are reacclimated to temperatures above 25C. These results indicate that snails that survive over winter, will likely serve as a source of infection during the subsequent growing season. This information has led to recommendations and the development of treatment strategies for the eradication of this disease. Enteric septicemia of catfish (ESC), caused by Edwardsiella ictaluri, is among the most prevalent and costly bacterial diseases affecting commercially produced channel catfish. Research was conducted to develop management strategies using restricted feeding practices and medicated feed to minimize losses associated with this disease. The combination of medicated feed and feed restriction was shown to reduce disease related losses by approximately 50%, compared to animals on full feed rations with and without added antibiotics. This information is being used to develop management strategies for controlling E. ictaluri infections that optimize growth and survival of channel catfish. Enteric septicemia of catfish (ESC), caused by Edwardsiella ictaluri, is among the most prevalent and costly bacterial diseases affecting commercially produced channel catfish. To reduce antibiotic use and morbidty associated with this disease, trials were conducted to evaluate a live attenuated E. ictaluri vaccine developed by USDA/ARS-Aquatic Animal Health Research Unit. Field and laboratory trials demonstrated vaccination was an effective method of reducing mortality and morbidity associated with ESC. Integrating vaccination into current disease management programs was shown to increase net profits by 400-1000 dollars per acre. Enteric septicemia of catfish (ESC) is among the most prevalent and costly bacterial diseases affecting the production of channel catfish. Since most disease treatments are effective in limiting the spread of the disease, effective control of ESC is dependent on early detection and prompt intervention. In efforts to improve treatment success, a quantitative polymerase chain reaction assay was developed for the early detection of E. ictaluri DNA in channel catfish blood. This technology is currently being used to develop a disease monitoring program to detect early stages of infection prior to the onset on mortality to alert farmers to impending epizootics. Proliferative gill disease is the third most diagnosed disease at the Thad Cochran National Warmwater Aquaculture Center-Aquatic Diagnostic Laboratory and can decimate entire populations of fish in production ponds. Research was conducted to evaluate the practice of using unproven biological and chemical treatments to prevent and control losses associated with this disease. To date, no treatments have been shown to be effective in preventing or controlling the severity of disease outbreaks. This information is being used to discourage ineffective treatments and practices that represent an unnecessary cost to production. Proliferative gill disease of channel catfish is a common disease in the spring of the year with the highest mortality rates occurring in fish that have been recently stocked into production ponds. To help minimize losses, methods were developed to monitor the occurrence and severity of the disease in commercial production ponds. Procedures used in this study were shown to be an accurate method of assessing the severity of infection and predicting the occurrence of PGD related losses. Application of these procedures in a disease management program can virtually eliminate PGD related losses in fish initially stocked into production ponds. One of the primary limitations to disease research is a lack of disease challenge models that duplicate typical field conditions, for the purposes of developing effective treatments and investigating the pathogenesis of various diseases. Research was conducted to develop procedures for inducing bacterial, parasitic, fungal and viral infections that reflect natural routes of infection and for monitoring the transmission of diseases in commercial production ponds. These disease challenge models and disease monitoring procedures have led to the establishment of best management practices to minimize losses associated enteric septicemia of catfish, columnaris disease, channel catfish virus disease, trematode infections, and fungal infections and are currently being used to evaluate potential treatments and improved disease management strategies. C. Significant accomplishments/activities that support special target populations Maintenance of catfish health improves production efficiency on U.S. catfish farms. The USDA Census of Aquaculture conducted in 2000 classified 84% of catfish farms as small businesses, with annual sales of less than $500,000. Of the 1,370 catfish farms in the United States, 38% (515) reported annual revenues of less than $25,000. Off-flavors disproportionately affect small farms because they are more susceptible to economic impacts related to interruption of cash flows and there is less probability of having acceptable fish to sell from at least one pond on the farm when only a few ponds are available. 5.Describe the major accomplishments over the life of the project, including their predicted or actual impact. Question 5: The catfish health research project was initiated on 8/01/2002 to develop a comprehensive disease management program that addresses disease related problems that threaten the economic viability of the channel catfish industry. This project will enhance the existing disease research and diagnostic programs at the Thad Cochran National Warmwater Aquaculture Center. The major accomplishments expected over the life of the project are to. 1)develop state of the art diagnostic tools and procedures to detect and monitor diseases in commercially raised channel catfish. 2)develop best management practices for improving fish health and limiting the economic impact of infectious and non-infectious diseases. 3)develop field and laboratory disease challenge models used to study the pathogenesis of infection and develop effective disease treatments, and. 4)establish a field service program to investigate new and emerging diseases, identify environmental and management factors that influence the onset and severity of disease outbreaks, and establish the epidemiology of economically significant diseases. 6.What do you expect to accomplish, year by year, over the next 3 years? Question 6: The major strength of the fish health program at the National Warmwater Aquaculture Center is its location at the epicenter of channel catfish industry. This proximity provides unparalleled access to the industry at the production level and opportunity for an applied emphasis approach to research and disease diagnostics. To develop this program it is essential to incorporate modern diagnostic tools and basic sciences into a multidisciplinary approach to optimize fish health. To achieve this goal it will be necessary to increase the research staff, to develop state of the art programs in diagnostics and field services, epidemiology, immunology, microbiology, and molecular biology. The expected research accomplishments of the fish health program over the next three years will be to. 1)establish a molecular biology laboratory incorporating conventional and quantitative polymerase chain reaction (PCR) technology, capabilities for protein and nucleic acid electrophoresic analysis, enzyme linked immunosorbent assay (ELISA) capabilities, and immunoblotting,. 2)develop rapid diagnostic tools using PCR technology for detection of disease causing agents responsible for proliferative gill disease and saprolegniasis,. 3)establish the epidemiology of channel catfish anemia, proliferative gill disease, saprolegniasis and visceral toxicosis of catfish,. 4)characterize the anemia responsible for channel catfish anemia based on morphologic changes in red blood cells and in blood forming elements,. 5)characterize the growth rates and molecular epidemiology of E. ictaluri isolates that exhibit atypical growth at elevated temperatures, indicating a possible divergence in the pathogenesis of this organism,. 6)determine the induction of proteins by fish intestinal and skin mucus in response to Edwardsiella ictaluri to identify protective immune responses,. 7)establish the molecular epidemiology of Edwardsiella ictaluri and Flavobacterium columnare and evaluate possible geographic patterns of antibiotic sensitivity,. 8)evaluate the use of bacteriophages as a possible control measure against bacterial infections.. 9)establish disease management programs utilizing restricted feeding practices, antibiotics and vaccines to minimize the impact of bacterial infections, and 10) develop risk assessment models using PCR technologies for proliferative gill disease and enteric septicemia of catfish to predict the occurrence of epizootics in commercial catfish ponds. 7.What science and/or technologies have been transferred and to whom? When is the science and/or technology likely to become available to the end-user (industry, farmer, other scientists)? What are the constraints, if known, to the adoption and durability of the technology products? Question 7: Information concerning the emergence of new diseases, and various disease management strategies has been disseminated to the appropriate user groups through trade journals, technical bulletins, newsletters, and extension workshops and publications. Scientific data that generated this information has also been presented in scientific journals and at professional meetings. Information concerning the cause and treatment of disease has been disseminated to producers through verbal communications during diagnostic and farm visits. On-site demonstration projects are also used to teach producers technical procedures that are effective in disease management. 8.List your most important publications in the popular press and presentations to organizations and articles written about your work. (NOTE: This does not replace your peer-reviewed publications listed below). Question 8: Avery, J., Wise, D. J., Terhune, J. S., Khoo, L. H. New trematode in channel catfish. Thad Cochran National Warmwater Aquaculture Center Fact Sheet Update 004. 2001. Bilodeau, A. L., Wise, D. J., Wolters, W. R. Early detection of Edwardsiella ictaluri in NWAC 103 channel catfish. Thad Cochran NWAC News. 2002. v. 5(2). Bilodeau, A., Wolters, W., Waldbiesser, G., Wise, D. A Real-time PCR Assay of the bacterium Edwardsiella ictaluri in channel catfish. 2002. Patent Disclosure No. 02-0804-14. Camus, A.C. Pathology of Bolbophorus-like trematode infections in channel catfish fingerlings. 8th Biennial Fish Diagnosticians Workshop. Stuttgart, Arkansas. 2002. Camus, A.C. Pathology of Aphanomyces invadans infections in channel catfish and bluegill. 8th Biennial Fish Diagnosticians Workshop. Stuttgart, Arkansas. 2002. Camus, A.C. Pathology of group C streptococcal infection in farmed tilapia. 8th Biennial Fish Diagnosticians Workshop. Stuttgart, Arkansas. 2002. Gaunt, P. Florfenicol antibiotic studies conducted. Thad Cochran NWAC News. 2002. v. 5(2). p. 2, 7. Gaunt, P. Schering-Plough reporting progress with florfenicol. The Catfish Journal. 2003. v. 17(10). p. 21. Huston, C.L., Khoo, L., Gaunt, P.S., Camus, A.C. Longitudinal monitoring of water quality parameters in commercial catfish ponds. Conference of Research Workers in Animals Diseases, St. Louis, Missouri. 2002. Khoo, L. Annual Fish Diagnostic Report. Thad Cochran NWAC News. 2002. v. 5(1). p. 6-7. Mischke, C.C., Li, M. H., Wise, D. J., Zimba, P. U. Zooplankton nutritional value:nursery pond fertilization effects. Thad Cochran NWAC News. 2002. v. 5(2). Mischke, C.C. and Wise, D. J. Zooplankton utilization by channel catfish fry. Thad Cochran National Warmwater Aquaculture Center News. 2001. v. 4(1). Mischke, C. M., Li, M. H., Wise, D. J., Zimba, P. Zooplankton nutritional values: Nursery pond fertilization effects. NWAC Fall Seminar, 2002. Wise. D. J. Cost Issues in Catfish Production and Industry Updates. NWAC Winter Seminar. 2002. Wise, D. J. Catfish parasite transmitted by pelicans. East Mississippi Ag Exposition. 2003. Wise, D. J. Vaccination of channel catfish against Edwardsiella ictaluri. 8th Biennial Fish Diagnosticans Workshop. Stuttgart, Arkansas. 2002. Wise, D. J. MSU research efforts on anemia. 8th Biennial Fish Diagnostcians Workshop. Stuttgart, Arkansas. 2002. Review Publications Bilodeau, A. L., Small, B. C., Waldbieser, G. C., Peterson, B. C., Wise D. J.,Wolters, W. R. Development and application of a real-time PCR pathogendection assay in channel catfish. Plant and Animal Genome XI Conference. San Diego, CA. January 11-15, 2003. Abstract p. 143.