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United States Department of Agriculture

Agricultural Research Service

Research Project: DAIRY MANAGEMENT PRACTICES AND THE TRANSMISSION OF ZOONOTIC PATHOGENS IN MILK
2007 Annual Report


1a.Objectives (from AD-416)
Objective 1 - Determine the environmental compartments within dairy farming systems that support the survival of the zoonotic pathogens Salmonella enterica, Escherichia coli, and Listeria monocytogenes and characterize their contribution to the pathogen content of milk.

Objective 2 - Characterize the role of management practices in the introduction and maintenance of Salmonella enterica, Escherichia coli, and Listeria monocytogenes on dairy farms and evaluate changes in management practices that might reduce or eliminate pathogens.

Objective 3 - Use molecular typing methods to determine the relationship between isolates of Listeria, Salmonella, and pathogenic E. coli from dairy cows, the farm environment, and from bulk tank milk with those known to have caused human disease.

Objective 4 - Develop new methods for the rapid and sensitive detection of Bacillus anthracis and Listeria monocytogenes in bulk tank milk and milk products.


1b.Approach (from AD-416)
Although pasteurization and regulations controlling the processing of any products made with unpasteurized milk have an excellent record of assuring the biological safety of dairy products marketed in the US, there is increasing concern about the presence of zoonotic pathogenic microorganisms in raw milk. For various cultural and economic reasons the consumption of raw milk and desire for products made from raw milk seems to be increasing and outbreaks of food-borne gastrointestinal disease due to contamination of dairy products have been documented. This project focuses on the ecology of the zoonotic bacterial pathogens Salmonella, Listeria monocytogenes, and Escherichia coli on dairy farms in the Northeastern United States, and the relationship of the pathogens found in farm animals and the farm environment with those found in bulk tank milk from those farms. Intensive longitudinal sampling will be performed on three ‘typical’ farms with collection of milk, milk filters, blood, feces, and various environmental samples. We will analyze samples for the three pathogens by both molecular and culture techniques; collaborators will analyze samples for MAP, Campylobacter, and enterococci. Molecular characterization techniques will be used to equate any pathogens found in bulk tank milk with those found on the farm. Management changes will be suggested to the farmers and the results of those changes will be documented. The relationships between Listeria monocytogenes from the farm and those associated with human disease will be investigated. Methods will be developed for improved detection of bacterial pathogens in milk and environmental samples.


3.Progress Report
The past year has seen the use of sophisticated molecular tracking techniques to identify and characterize farm isolates of Listeria, Salmonella and E. coli. The longitudinal study of Salmonella, E. coli, and Listeria monocytogenes has continued with samplings increased as required to fully define outbreaks. This, along with participation in the NAHMS 2007 dairy survey has helped to provide a national view of these pathogens on the U.S. dairy farm. It has also provided a mechanism to track pathogens in their various niches on the farm. With access to three specific farms through our collaboration with four northeastern Universities, the laboratory is in a position to become a leader in characterizing molecular epidemiological relationships among a host of important dairy pathogens.


4.Accomplishments
A 2 year, in-depth study of an outbreak of Salmonella enterica serotype Cerro on a dairy farm was completed. The study demonstrated that this strain of Salmonella acts as a commensal organism in dairy cows, causing no apparent illness or drop in milk production. A study done with samples from the same farm demonstrated that the milk filter is a sensitive indicator of Salmonella shedding in a dairy herd. Addresses Program 108 objectives related to action plan component 1.1.1: sampling, isolation, identification and quantification of pathogens in animal fluis and tissues, manure, and the environment, including feed, water, and wild animals.


5.Significant Activities that Support Special Target Populations
None


6.Technology Transfer

Number of non-peer reviewed presentations and proceedings2

Review Publications
Chapagain, P.P., Van Kessel, J.S., Karns, J.S., Wolfgang, D.R., Hovingh, E., Nelen, K., Schukken, Y.H., Grohn, Y.T. 2007. A mathematical model of the dynamics of Salmonella Cerro infection in a U.S. dairy herd. Epidemiology and Infection. Available: http://Journals.Cambridge.org.

Karns, J.S., Van Kessel, J.S., McClusky, B.J., Perdue, M.L. 2007. Incidence of Escherichia coli O157:H7 and E. coli Virulence Factors in U.S. Bulk Tank Milk as Deteremined by Polymerase Chain Reaction. Journal of Dairy Science. 90:3212-3219.

Last Modified: 9/23/2014
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