Submitted to: Epidemiology and Infection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/3/2003
Publication Date: 2/20/2004
Citation: HURD, H.S., MCKEAN, J.D., GRIFFITH, R.D., ROSTAGNO, M.H. ESTIMATION OF THE SALMONELLA ENTERICA PREVALENCE IN FINISHING SWINE. EPIDEMIOLOGY AND INFECTION. 2004. V. 132. P. 127-135.
Interpretive Summary: It is critical to measure the number of Salmonella infected swine on a farm, for research and intervention purposes. Only a limited number of methods are available. A comparison of those methods is needed. The fecal sample, which is the most commonly used method, severely underestimates the true number of infected animals on a farm. Samples collected at the abattoir do not accurately reflect the on-farm prevalence due to infection of the pigs in the holding pens, shortly before slaughter. This study demonstrates that better methods are needed before preharvest Salmonella research can progress. This research is of benefit to scientists, packing plants, pork producers, practitioners, and APHIS and FSIS.
Technical Abstract: The study objective was to evaluate three methods of Salmonella enterica prevalence estimation in swine herds (fecal culture, culture of abattoir collected samples, and serum ELISA). From each of six swine herds, we necropsied ~100 finishing pigs (> 70 Kg); one-half on-farm and the other half at the abattoir, after transport and ~ 2.5 hours holding. We collected the same samples for S. enterica culture at both locations (1 g fecal, 10 g cecal contents, ileocecal lymph nodes, superficial inguinal lymph nodes, 25 g of gluteal muscle for serum ELISA). On-farm, the 1 g fecal sample only detected 13.3% (2 of 15) of all infected pigs. However, with abattoir and on-farm results combined, the fecal sample detected 57.4% (74/129) of infected pigs. Abattoir collected samples provided prevalence estimates much higher than on-farm collected samples (39.9% versus 5.3%; P < 0.001). This study shows that fecal samples have a low sensitivity for detecting infected pigs and that abattoir collected samples will overestimate the farm S. enterica prevalence.