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United States Department of Agriculture

Agricultural Research Service

Research Project: Pathogen Surveillance, Control and Vaccine Use on Fish Farms in the Southeastern U.S

Location: Aquatic Animal Health Research

2011 Annual Report

1a. Objectives (from AD-416)
The objective of this project is to conduct pathogen surveillance, control and development and use of vaccines on fish farms in the Southeastern U.S. The work will include surveillance and monitoring, development of prevention or control methods to prevent the spread of diseases, and development and evaluation of vaccines against virulent strains of Aeromonas hydrophila.

1b. Approach (from AD-416)
Work closely with the Auburn University's Department of Fisheries and Allied Aquacultures (AU-DFAA) to conduct pathogen surveillance, epidemiology, control and vaccine research. By applying appropriate tools of epidemiology, pathogen control and vaccinology in responses to new outbreaks of A. hydrophila, it is possible to identify putative factors associated with fish disease outbreaks. Aeromonas hydrophila surveillance and epidemiological research will be conducted using diagnostic tests. ARS will be responsible for epidemiology (including surveillance and monitoring research) and work closely with the professional staff at Fish Farming Center and diagnostic laboratory of AU-DFAA. AU-DFAA will assist ARS with identification of, and access to, work site farms. AU-DFAA and ARS will be responsible for identification of A. hydrophila isolates collected from these and other affected farms. Molecular, microbiological and vaccinology methods will be used to develop fish vaccines that may be given in mass scale. ARS will be responsible for the development of the vaccine and its evaluation in experimental wet laboratory trials. The vaccines will be evaluated under field conditions in farm ponds and in pond raceways. ARS and AU-DFAA will be equally responsible for vaccination and monitoring of catfish for effectiveness of vaccination at the work site farms and experimental ponds. Prior to presentation or publication of data resulting from collaborative efforts related to this agreement, ARS and AU-DFAA must agree to order of authorship content. This approach will expedite the control of A. hydrophila that is responsible for significant economic losses in the Southeastern U.S. fish farms. Furthermore, the public will benefit by having a readily available safe source of protein.

3. Progress Report
The catfish industry suffers an annual loss of almost 100 million dollars from disease problems alone. One focus of our studies has been to understand genes involved in disease resistance in catfish that fall into two main categories, one involving disease resistance genes in host or catfish, the second one involving the genes of disease causing agents or the parasite. We have characterized four genes, ceruloplasmin, calreticulin, ferritin H subunit and matrix metalloprotein-13 genes from catfish, determined their genomic organization, profiled their patterns of tissue expression, and established some of their potential for immune responses after bacterial infection with Edwardsiella (E.) ictaluri and/or iron treatment. Expressions of all four genes are strongly up-regulated during challenge with E. ictaluri. The ciliate protozoan Ichthyophthirius multifiliis (Ich) is a teleost parasite affecting many freshwater fish species causing white spot disease. In order to study gene expression involved in Ich virulence, we have generated a total of 8,432 high quality sequences for the analysis of global gene expression using three life stages. We have also focused on the evaluation of novel biological control strategies to prevent and limit mortalities associated with bacterial pathogens. This project has primarily centered around the use of a recently isolated bacteriophage that is lytic to Edwardsiella ictaluri, one the the most economically damaging pathogens affecting catfish culture in the U.S. and Southeast Asia. The second major focus area is the evaluation of virulence mechanisms associated with a new, emerging strain of Aeromonas hydrophila, that has killed millions of pounds of catfish in West Alabama and has been documented as spreading to other areas of the U.S. New vaccine candidates against the catfish pathogen Flavobacterium (F.) columnare have also been developed. Some of these new avirulent mutants have shown to confer more protection against columnaris disease than currently available vaccines. Safety and efficacy of these vacccines have been proven in channel catfish and ornamental fish species. Newly formulated buffers allow maintaining the vaccines at room temperature for several months without the need to freeze or lyophilize the live cultures. Studies on pathogenic factors in F. columnare included in vivo and in vitro adhesion and chondroiting lyase activity. We have found significant differences in adhesion of F. columnare genomovars to different hosts while adhesion in vitro has shown no correlation with genomovar ascription. Marked significant differences in chondroitin activity have been found in our collection of isolates with no correlation with virulence. The work and monitoring of this agreement is conducted with collaborative work, e-mails and phone calls.

4. Accomplishments

Last Modified: 06/26/2017
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