2012 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.
Cooperating staff at Auburn University, Department of Fisheries and Allied Aquacultures, Auburn, AL, continue to provide studies on columnaris disease. Scientists have optimized vaccination and challenge protocols for catfish (including channel, blue and hybrid catfish), ornamental species, tilapia and sport fishing species. The efficacy of two avirulent-mutants as vaccines against columnaris diseases has been tested in catfish fry, catfish fingerlings, zebrafish, and tilapia. In addition, scientists are conducting investigation into the epidemiology (prevalence and distribution) of high virulent strains of Flavobacterium (F.) columnare in freshwater ecosystems and aquaculture environments. In other investigations, results show that the virulence of an Aeromonas hydrophila emerging strain to channel catfish (90%) is significantly higher than to blue (50%) and hybrid catfish (65%). No significant differences were observed between blue and hybrid catfish. Further investigation will be conducted into the mechanisms for disease as well as susceptibility of other fish species. An epidemic outbreak of motile Aeromonas septicemia (MAS) caused by Aeromonas (A.) hydrophila is a major threat to the catfish industry in the southeastern United States. Researchers will provide further studies into the evolutionary changes in A. hydrophila strains associated with epidemic outbreaks in channel catfish and provide a foundation for studying the specific molecular determinants of virulence in this emerging pathogen.