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Title: Salmonella prevalence and antimicrobial susceptibility from the national animal health monitoring system sheep 2011 study

Author
item DARGATZ, DAVID - Animal And Plant Health Inspection Service (APHIS)
item MARSHALL, KATHERINE - Animal And Plant Health Inspection Service (APHIS)
item FEDORKA-CRAY, PAULA - Former ARS Employee
item ERDMAN, MATTHEW - Animal And Plant Health Inspection Service (APHIS)
item KOPRAL, CHRISTINE - Animal And Plant Health Inspection Service (APHIS)

Submitted to: Foodborne Pathogens and Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/5/2015
Publication Date: 12/5/2015
Citation: Dargatz, D.A., Marshall, K.L., Fedorka-Cray, P.J., Erdman, M.M., Kopral, C.A. 2015. Salmonella prevalence and antimicrobial susceptibility from the national animal health monitoring system sheep 2011 study. Foodborne Pathogens and Disease. 12(12):953-957.

Interpretive Summary: Salmonella is a major cause of foodborne disease in humans and can also affect production of farm animals. Very little is known about the occurrence of Salmonella in sheep and this study was undertaken to determine how often sheep are infected with Salmonella and to characterize the Salmonella that was found for its type and whether it was resistant to antimicrobial treatment. 3722 fecal samples were collected from 247 farms in 22 states. 72.1% of the farms had at least one sample positive for Salmonella and 26.9% of all the samples were positive. Ewes that were nursing lambs were most likely to be infected. Antimicrobial resistance was rare among the observed isolates. The vast majority of the Salmonella that were isolated were of the type known as Salmonella enterica subspecies diarizonae. This is a type that is rare outside of sheep. Thus, the salmonellae typically associated with foodborne disease transmission are infrequently found on sheep operations in the United States.

Technical Abstract: Salmonella is a major cause of foodborne illness and can cause clinical disease in animals. Understanding the on-farm ecology of Salmonella will be helpful in decreasing the risk of foodborne transmission. An objective of this study was to determine the prevalence of Salmonella among fecal samples collected on sheep operations in the United States. Another objective was to compare the use of composite fecal samples with fecal samples collected from individual sheep as a tool for screening sheep flocks for Salmonella. Sheep fecal samples (individual and composite) were collected on operations in 22 states. Salmonella isolates were characterized with regard to species, serotype, and antimicrobial susceptibility profile. Most operations (72.1%) had at least one positive sample and overall 26.9% of samples were positive. The percentage of positive samples varied by animal age class. Composite and individual samples gave similar results. The majority of the isolates (94%) were Salmonella enterica subspecies diarizonae serotype 61:-:1,5,7. Nearly all of the isolates (91.2%) tested for antimicrobial susceptibility were susceptible to all antimicrobials in the panel. The findings suggest that salmonellae typically associated with foodborne disease transmission are infrequently found on sheep operations in the United States.