Location: Aquatic Animal Health Research2011 Annual Report
1a. Objectives (from AD-416)
Objective 1 - Determine population and strain responses to vaccines and infectious pathogens (e.g., Edwardsiella ictaluri, Flavobacterium columnare), using genetically characterized fish. Objective 2 - Determine characteristics of coinfections and their role in disease processes in aquaculture and aquatic environments. Objective 3 - Identify microbial pathogen genes and pathways critical for host pathogenesis and immunity. Objective 4 - Develop and validate new and novel pathogen detection tests for Edwardsiella ictaluri, Flavobacterium columnare, Streptococcus iniae and S. agalactiae using genomic, proteomic, microbiological and immunological approaches.
1b. Approach (from AD-416)
Fish farmers continue to identify disease as a significant negative impact on profitability. Therefore, the goal of this project is to improve fish health and reduce this negative impact. Using a multi-disciplinary approach, we will accomplish four objectives that address important questions about bacterial diseases that affect the catfish (e.g., Edwardsiella ictaluri, Flavobacterium columnare) and tilapia (e.g., Streptococcus iniae, S. agalactiae) industries. Studies will be conducted at the gene, protein, individual, and/or population levels. Questions remain about some barriers to optimum vaccine efficacy in the field and about the responses of current and future strains of fish to pathogens and vaccines. Therefore, Objective 1 will determine population and strain responses to vaccines and infectious pathogens (e.g., E. ictaluri, F. columnare), using genetically characterized fish. In most intensive aquaculture production systems, multiple pathogens are present and result in mortality. Objective 2 will determine characteristics of coinfections and their role in disease processes in aquaculture and aquatic environments. Objective 3 will identify microbial pathogen genes and pathways critical for host pathogenesis and immunity that will provide important information for future vaccine development. Objective 4 will develop and validate new and novel pathogen detection tests for E. ictaluri, F. columnare, S. iniae and S. agalactiae so that these can be used in fish health management. The results from this work will contribute to present and future vaccine development, provide useful management information about farm use of vaccines and coinfections, and leverage development of future catfish strains being developed for the industry.
3. Progress Report
Significant progress was made to evaluate the acquired immune response of channel catfish using microarray and genomic technologies following immunization with modified live Edwardsiella (E.) ictaluri and Flavobacterium (F.) columnare vaccines. Microarray and genomic data have been obtained and data analyses are being conducted. Significant progress was made to evaluate channel catfish families which have been selectively bred for resistance against E. ictaluri for susceptibility to F. columnare. All experiments have been completed and no significant disease resistance differences were found between families. Progress was made to determine risk factors for disease and for vaccine efficacy on the catfish farm. Analyses of National Animal Health Monitoring System (NAHMS) data have been completed and Aeromonas (A.) hydrophila field data have been collected. Significant progress was made to determine the effect of parasitism on the susceptibility of channel catfish to E. ictaluri infection, and it has been found that dual infection of protozoan parasite Ich and E. ictaluri significantly increased fish mortality compared to fish only infected by E. ictaluri or only infected by Ich. Significant progress was made to determine whether parasites vector bacterial pathogens of fish. Polymerase Chain Reaction (PCR) assays have been successfully modified and developed to detect bacteria in parasite or fish tissues. Significant progress was made to identify proteins of F. columnare that are differentially regulated following growth in vivo or in media mimicking in vivo conditions and determine their role in pathogenesis. Culture of F. columnare has been completed. Significant progress was made to identify host genes critical for immunity against infectious pathogens and vaccines using subtractive hybridization technique. Studies on immune gene response in channel catfish to F. columnare vaccines have been completed and published. Significant progress was made to construct, produce, and use partial Aeromonas hydrophila protein arrays to investigate the catfish immune response to A. hydrophila. Primers have been designed and genes have been PCR amplified. In addition, expression plasmid constructs have been made. Significant progress was made to develop and evaluate attenuated vaccines to protect catfish and tilapia against Streptococcus (S.) iniae, S. agalactiae, E. tarda, and A. hydrophila. Studies on safety, efficacy, and immunodose of promising S. iniae vaccine in tilapia have been completed and published. In addition, patent application on the promising S. iniae vaccine has been filed. Attenuated S. agalactiae mutants have been produced and studies on their attenuation profiles have been completed. Significant progress was made to develop and evaluate recombinant vaccine against the protozoan parasite Ich. Preparation of recombinant protein IAg has been completed.
1. Vaccine developed to protect fish against streptococcal disease. Streptococcus (S.) iniae is a causative agent of streptococcal diseases that are threatening the aquaculture industry worldwide. Estimated economic impact from infections caused by streptococcal diseases is at least $100 million globally. Methods to control streptococcal diseases in fish include the use of antibiotics. However, antibiotics are expensive and usually ineffective because sick fish normally do not eat. Therefore, an alternative method to control streptococcal disease is urgently needed. ARS scientists at Auburn, AL, have developed a highly effective vaccine to protect fish against streptococcal diseases. Studies on safety, efficacy, and immunization dose of the vaccine have been published. In addition, a patent application on the vaccine has been filed. The use of this vaccine will significantly benefit fish farmers and the aquaculture industry.
2. Vaccine developed to protect fish against columnaris disease. Flavobacterium (F) columnare is the causative agent of columnaris disease. Columnaris disease is threatening both warm water and cold water fish worldwide. Annually, columnaris disease is responsible for economic losses of at least $30 million to fish farmers. To control bacterial diseases, use of antibiotics is a general method. However, antibiotics are too expensive. In addition, frequent use of antibiotics has lead to the development of antibiotic-resistance in fish pathogen. Therefore, alternative methods to control bacterial diseases are urgently needed. ARS scientists at Auburn, AL, developed an attenuated live vaccine against columnaris disease, which offered significant protection for both channel catfish and largemouth bass. This vaccine has been commercially licensed to prevent columnaris disease to benefit fish farmers and the aquaculture industry.
Wei Pridgeon, Y., Klesius, P.H. 2010. Identification and expresion profile of multiple genes in channel catfish fry ten minutes after modified live Flavobacterium columnare vaccination. Veterinary Immunology and Immunopathology. 138:25-33.