Submitted to: Research Workers in Animal Diseases Conference Proceedings
Publication Type: Abstract only
Publication Acceptance Date: 10/4/2004
Publication Date: 11/14/2004
Citation: Rostagno, M.H., Hurd, H.S., McKean, J.D. 2004. Bacteriological and serological Salmonella prevalence in finishing pigs [abstract]. Conference of Research Workers in Animal Diseases. p. 121. Interpretive Summary:
Technical Abstract: This study consisted of an on-farm survey to determine the Salmonella enterica infection prevalence in finishing pigs from multiple production sites. The aim was to evaluate the stability of Salmonella prevalence (bacteriological and serological) in finishing pig groups produced by each site. Six finishing production sites were visited 6 times each, where market-aged swine were sampled. For each group of pigs, 30 individual fecal samples were collected on-farm, and 50 individual meat samples (diaphragm) were collected at the abattoir. Fecal samples were selectively enriched, and analyzed for the presence of Salmonella enterica. Meat samples were frozen and thawed, and the resulting liquid ("meat juice") was collected and analyzed for the presence of antibodies against Salmonella. All finishing production sites were Salmonella-positive in at least 2 fecal (bacteriological) and 4 meat (serological) samplings. The overall bacteriological prevalence of Salmonella-positive pigs was 12.9% (95% C.I. 8.0 - 17.8%), whereas the serological prevalence found was 35.4% (95% C.I. 24.5 - 46.4%). Although the overall prevalence estimated by fecal and meat samplings differed (p < 0.05), a Pearson's correlation coefficient (r) of 0.64 (p < 0.01) was found. A striking result found in this study consisted in a wide variation in the Salmonella prevalence (bacteriological and serological) from different finishing pig groups within individual production sites. The wide variation found did not allow the categorization of the sites (statistically) as high or low prevalence. Possible reasons for the wide variation found within production sites are: 1) occurrence of intermittent shedding and clusters, and 2) evolution and resolution of Salmonella infection epidemics. This study demonstrates that both, bacteriological and serological estimates of Salmonella enterica prevalence in swine production systems are not consistent among cohorts over time, and also, that Salmonella infections in swine populations are very dynamic. As a direct consequence of the results obtained in this study, a critical question remains: Are there high and low Salmonella prevalence sites, or is it just a matter of timing?