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Title: Longitudinal study of a clonal, sub-clinical outbreak of Salmonella enterica subsp. enterica Serovar Cerro in a US dairy herd

Author
item Van Kessel, Jo Ann
item Karns, Jeffrey
item WOLFGANG, D - PENN STATE U.,U.PARK,PA
item HOVINGH, E - PENN STATE U.,U.PARK,PA
item SCHUKKEN, Y - CORNELL U.,ITHACA,NY

Submitted to: Foodborne Pathogens and Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/16/2007
Publication Date: 12/1/2007
Citation: Van Kessel, J.S., Karns, J.S., Wolfgang, D.R., Hovingh, E., Schukken, Y. 2007. Longitudinal study of a clonal, sub-clinical outbreak of Salmonella enterica subsp. enterica Serovar Cerro in a US dairy herd. Foodborne Pathogens and Disease. 4(4):449-461.

Interpretive Summary: Salmonella are a major group of food-borne pathogens known to affect both man and animals. Dairy cattle are a known reservoir of these bacteria and human Salmonella infections have been associated with the consumption of improperly processed dairy products. Many of the over 2000 known serotypes of Salmonella are known to infect cattle producing symptoms ranging from none to death. This study describes the course of a Salmonella outbreak on a single dairy farm in Pennsylvania. The outbreak was detected when a few cows were found to be infected with serotype Typhimurium var. copenhagan which caused clinical symptoms and one fatality. Based upon sampling of the farm environment, Typhimurium var. copenhagan was succeeded within three months by serotype Kentucky. Serotype Cerro ultimately supplanted Typhimurium var. copenhagan and Kentucky in individual animals and environmental samples and has remained in the herd at high prevalence for 18 months with no obvious clinical consequences. These data suggest that some serotypes of Salmonella can behave as normal gut inhabitants in dairy cattle and illustrate the difficulties of controlling Salmonella on dairy farms. Although serotype Cerro has not been seen as a major source of human illness, all Salmonella are considered human pathogens and an understanding of the factors that allow this bacterium to survive on the dairy farm may lead to the discovery of management tools to eliminate it and make dairy products even safer than they are today.

Technical Abstract: Salmonellae are a major group of food-borne pathogens known to affect both man and animals. Dairy cattle are a known reservoir of these bacteria and human Salmonella infections have been associated with the consumption of improperly processed dairy products. Many of the over 2000 known serotypes of Salmonella are known to infect cattle producing symptoms ranging from none to fatal salmonellosis. This study describes the course of a Salmonella outbreak on a single dairy farm in Pennsylvania. The outbreak was detected when a few cows were found to be infected with Salmonella enterica enterica Typhimurium var. copenhagan which caused clinical symptoms and one fatality. Based upon sampling of the farm environment, Typhimurium var. copenhagan was succeeded within three months by Salmonella enterica enterica Kentucky. Salmonella enterica enterica Cerro ultimately supplanted Typhimurium var. copenhagan and Kentucky in individual animals and environmental samples and has remained in the herd at high prevalence for 18 months with no obvious clinical consequences. These data suggest that some serotypes of Salmonella enterica enterica can behave as commensal organisms in dairy cattle and illustrate the difficulties of controlling Salmonella in milk production systems.