Epidemiology and Infection

Original Papers


Longitudinal study of Salmonella shedding in naturally infected finishing pigs

A. F. A. PIRESa1 c1, J. A. FUNKa1 and C. A. BOLINa2

a1 Department of Large Animal Clinical Sciences, College of Veterinary Medicine, Michigan State University, East Lansing, MI, USA

a2 Diagnostic Center for Population and Animal Health, College of Veterinary Medicine, Michigan State University, East Lansing, MI, USA


A 3-year longitudinal study was conducted on a multi-site farrow-to-finish production system. For each of 18 cohorts at three finishing sites, 50 pigs were randomly selected. Faecal samples were collected every 2 weeks for 16 weeks. Salmonella was cultured from 453 (6·6%) of 6836 faecal samples. The pig-level incidence of Salmonella was 20·8% (187/899 pigs). Salmonella prevalence varied between cohorts and within pigs. The adjusted Salmonella prevalence decreased over the finishing period from 6·4% to 0·8%. Intermittent detection of Salmonella was found in more than 50% of pigs that were positive at more than one collection. The finding that the majority of pigs shed intermittently has implications for surveillance and research study design when determining Salmonella status. The variability in shedding over time, as well as between and within cohorts and pigs suggests that there may be time-variant risk factors for Salmonella shedding in swine.

(Received June 07 2012)

(Revised September 18 2012)

(Accepted October 10 2012)

(Online publication November 13 2012)

Key words

  • Longitudinal;
  • Salmonella ;
  • swine


c1 Author for correspondence: Dr A. F. A. Pires, Food Safety and Toxicology Building, 1129 Farm Lane B 41, East Lansing, MI 48824-1314, USA. (Email: afapires11@gmail.com)