2011 Annual Report
1a.Objectives (from AD-416)
The overall objective of this cooperative research project is to determine risk factors for vaccine efficacy on catfish farms. Two modified-live vaccines, which were developed at the USDA ARS AAHRU, are available for use by the catfish industry: AQUAVAC-COL (Intervet/Schering-Plough), an aid in the prevention of columnaris disease in catfish due to F. columnare infection, and AQUAVAC-ESC (Intervet/Schering-Plough), an aid in the prevention of enteric septicemia of catfish due to E. ictaluri infection. Laboratory and some efficacy field studies for these vaccines have been published. When vaccines are used on the farm, efficacy can be different than was demonstrated in the laboratory, and can vary from farm to farm. There are many possible explanations for variations in vaccine efficacy when used on the fish farm, including immunosuppression (e.g., due to poor nutrition or poor quality culture environment), and the effect of an overwhelming challenge dose. These factors can be directly related to farm management, with the farm that is managed according to best practices arguably being most likely to experience the greatest benefit from vaccination. If this relationship can be demonstrated, then farmers may be able to increase vaccine efficacy on their farm by improving these practices.
1b.Approach (from AD-416)
A whole-population cross-sectional survey of Alabama, Mississippi, Louisiana, and Arkansas catfish farmers will be used to evaluate putative risk factors that contribute to vaccine efficacy on the catfish farm. Other fish health questions may also be evaluated. The data will be obtained from the 2010 National Animal Health Monitoring System (NAHMS) Catfish Survey, conducted by the U.S. Department of Agriculture, Animal Plant Health Inspection Service, Veterinary Services (USDA, APHIS, VS). Risk factors to be explored will include stocking densities, feeding practices (frequency during winter, form of feed fed, withholding feed during disease outbreak), pond renovation/fallowing/preparation procedures, aerator use, farm size, and record keeping. In addition to descriptive summaries of results, multi-variable regression analysis with potential outcome variables being perceived change in disease loss before and after the use of vaccination, and level of producer satisfaction with the vaccine, will be used to analyze the data. If there are not enough farmers using vaccinated fish in the four states, the number of risk factors in the analysis may be reduced to achieve the statistical power necessary for the regression analysis. Alternatively, survey results will be published as a univariate analysis and/or as a descriptive survey of the use of vaccination by the U.S. catfish industry.
The 2010 National Animal Health Monitoring System Catfish Survey of the U.S. catfish industry was completed by USDA, APHIS early in 2010. Data for analysis of risk factors for vaccine efficacy was transferred to the USDA, ARS in July, 2010. Sample sizes for producers using vaccination were too small to accomplish the original objective. However, the ARS lead investigator and the APHIS co-lead investigator analyzed the available data and wrote a manuscript describing use of vaccination by the catfish industry. Project activities and progress were monitored through the use of telephone calls and e-mails.