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Animal-Level Predictors of Multiply Drug-Resistant Salmonella Carriage by Cull Dairy Cattle

Investigators
McCarthy, Rebecca; Loneragan, Guy; Besser, Thomas; Nisbet, David; Edrington, Thomas; Brashears, Mindy; Daniels, Angela
Institutions
Texas Tech University
Washington State University
USDA - Agricultural Research Service
West Texas A&M University
Circle H Animal Health LLC
Start date
2008
End date
2009
Objective
Salmonella is an important cause of food-borne illness in the US and beef has been identified as a source. Culled dairy cows are a significant source of beef products, particularly ground beef, and they also frequently carry Salmonella. Understanding factors that contribute to Salmonella carriage in dairy cattle is important for control purposes.

This study was undertaken to estimate herd-level burden and identify animal-level predictors of Salmonella carriage in dairy cattle of the southern High Plains.

More information
Findings: Animals harbor multiple serovars in their feces and to an even greater extent on their hides. In other words, Salmonella appears ubiquitous in cattle populations of the Texas High Plains. Salmonella burden appears to be driven primarily by herd-level factors. The consequence of which is that individual-level factors are relatively meaningless when the likelihood of being Salmonella positive depends primarily in which herd the animal is housed. While not designed to evaluate herd-level determinants, one such factor may be the use of SRP-containing vaccine as those dairies that practiced whole-herd vaccination had an 81% lower prevalence compared to those herds that did not vaccinate (RR=0.19; P < 0.01). Beyond vaccine use, however, substantial farm-to-farm variation is evident and further research is warranted to a) evaluate effect of the vaccine at the herd-level; and b) uncover other herd-level factors that drive Salmonella burden.
Funding Source
Nat'l. Cattlemen's Beef Assoc.
Project number
BC-2008-2
Categories
Natural Toxins
Bacterial Pathogens