Lesion Severity at Processing as a Predictor of Salmonella Contamination of Pig Carcasses

The presence of lesions may be used to predict Salmonella contamination of pig carcasses, according to new research from Iowa State University. They also found that non–experts on the processing line could use their assessment of the lesions to discriminate between healthy and ill animals before the pigs entered the food chain.
calendar icon 15 March 2012
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In a paper published recently in American Journal of Veterinary Research, Dr Scott Hurd of Iowa State University and co-authors there and at Michigan State University state that the objective of their work was to measure the relationship between gross lesions in pig carcasses observed at a processing plant and Salmonella contamination and to determine whether non–expert assessments of lesion status would correspond with swine pathologists’ judgments.

Carcasses of 202 conventionally raised and 156 antimicrobial–free pigs were examined between December 2005 and January 2006 in a Midwestern US processing plant.

Four replicates were conducted. For each, freshly eviscerated carcasses were identified as having or lacking visceral adhesions by a non–expert evaluator and digital carcass photographs were obtained. Swab specimens were obtained from carcasses before the final rinse stage of processing, and bacterial cultures for Salmonella spp and Enterococcus spp were performed. Subsequently, carcass photographs were numerically scored for lesion severity by three veterinary pathologists. The results were used to test the ability of lesion detection to predict bacterial contamination of carcasses and the agreement between judgments of the inexperienced and experienced assessors.

The researchers found that the probability of Salmonella contamination in carcasses with lesions identified at the abattoir was 90 per cent higher than that in carcasses lacking lesions, after controlling for replicate identity and antimicrobial use. The receiver operating characteristic curve and Cohen K indicated close agreement between lesion detection at the abattoir and by the three pathologists.

Hurd and co-authors state that their findings indicated the presence of lesions could be used to predict Salmonella contamination of pig carcasses and that a non–expert processing–line assessment of lesions could be used to discriminate between healthy and chronically ill swine before their entry into the human food supply.


Hurd H.S., M.J. Yaeger, J.M. Brudvig, D.D. Taylor and B. Wang. 2012. Lesion severity at processing as a predictor of Salmonella contamination of swine carcasses. American Journal of Veterinary Research, 73(1):91-97. doi:10.2460/ajvr.73.1.91

Further Reading

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March 2012
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