1a. Objectives (from AD-416):
The objective of this agreement is to build upon a long-term project designed to evaluate the impact of intervention strategies on Johne’s disease dynamics, milk and beef quality (particularly with respect to zoonotic bacterial pathogens), economics and sustainability through intensive longitudinal follow up of well-characterized research/demonstration dairy farms. Long-term goals are to validate intervention strategies to support best management practices (BMPs) and to optimize intervention and monitoring strategies given the constraints on time, labor and financial resources in modern dairy herds. In addition, a national resource bank (data and biological specimens on well-characterized animals) will be maintained for current and future monitoring and research on dairy cattle diseases. Emphasis will be on longitudinal data collection on endemic infectious diseases of public and animal health concern.
1b. Approach (from AD-416):
Pathogens are of increasing concern on dairy farms and in dairy products. The production of safe and wholesome food from U.S. farms requires control of the production process on the farm. Specific focus areas in this process are biosecurity, food safety and animal health. To be able to scientifically support regional process control programs there is a need for longitudinal research on commercial dairy farms throughout the United States. For several years, Cornell University, the Pennsylvania State University, the University of Vermont, and the University of Pennsylvania, which are all participants in the Regional Dairy Quality Management Alliance (RDQMA), have collaborated with the USDA’s Environmental Microbial Safety Laboratory to study the disease dynamics of endemic infectious diseases on three operating dairy farms. The goal is to identify sites that act as reservoirs for pathogenic microorganisms that affect animal health and/or decrease product quality because of their zoonotic nature. Serum, feces, bulk tank milk, and environmental samples (water, bird and rodent feces, feed, etc.) will be taken on the farm. In addition, tissue samples will be obtained from carcasses of culled animals. Samples will be distributed among the university and ARS researchers for analysis to determine the presence of Mycobacterium avium paratuberculosis (the causative agent of Johne’s disease in cattle) and for Salmonella enterica, Escherichia coli O157:H7 and other enteropathogenic forms of E. coli, and Listeria monocytogenes (human food-borne pathogens of concern in dairy products). This research is the first to attempt a comprehensive analysis of both Johne’s disease and food-borne pathogens on working dairy farms. We have gathered extensive baseline data for these organisms on three farms and have set the stage for investigation of the effect of interventions, in the form of BMPs, on animal health and product quality.
3. Progress Report:
Through this agreement the cooperators provided veterinary expertise and access to samples from dairy farms and slaughterhouses in Pennsylvania for the study of the occurrence, maintenance, and persistence of Salmonella, Listeria monocytogenes, and pathogenic E. coli within the dairy chain. This longitudinal study has demonstrated the nature of long term colonization of dairy herds by Salmonella serotypes Cerro and Kentucky. A vaccine used for the treatment of acute Salmonella infections in cows was tested to determine if it might be useful in the control of commensal infections by Cerro and Kentucky. The vaccine had little or no effect on carriage of these commensal serotypes. Milk, milk filter, fecal, and environmental samples were taken and distributed to participant laboratories as required. Weekly milk samples from participant farms were analyzed for milk quality indicators. They also collected fecal material from cull dairy cows at farms, buying stations, and processing plants as part of a pilot study conducted as a collaboration between USDA/ARS, Food and Drug Adminstration/Center for Veterinary Medicine (FDA/CVM), and several universities to assess antibiotic resistance in bacteria harbored by food-producing animals. The samples collected and the work done throughout the course of this agreement have been instrumental in demonstrating the utility of in-line milk filters for detection of Salmonella on dairy farms, the regional distribution of infections by cow-adapted Salmonella on dairy farms, the transient nature of E. coli O157:H7 infections in lactating dairy animals, and the low rate of antibiotic resistance in Salmonella and E. coli on dairy farms in the Northeast U.S.