Frequencies of Salmonella enterica in Growing Pigs in Paraguay

Abstract

The objective of this study was to (1) estimate frequencies of Salmonella enterica in growing pigs and (2) investigate farmers? perception and practices towards pig farming in Central Department, Paraguay. Twelve out of 19 districts in the department were selected and 33 farms with growers in the selected districts were recruited. Questionnaire interviews for each study farm, in combination with faecal sample collections (n = 30 per farm), which were microbiologically examined and visual inspection of pig production facilities were performed between March and November 2009. A questionnaire was designed to obtain basic information of a farm such as the number of pigs owned and some selected farming management practices. Faecal samples were used for Salmonella isolation, using buffered peptone water to have salmonellae pre-enriched, followed by xylose lysine tergitol 4 agar and brilliant green sulfapyridine agar. Suspect colonies were biochemically tested by triple sugar iron agar in combination with lysine iron agar to confirm the identity. The true frequency probability and associated 95% Bayesian credible intervals (95% BCI) were computed via the Gibbs sampler, a Markov chain Monte Carlo technique. Overall, 18% (95% BCI: 8-31%) of the tested 1000 faecal samples were classified as positive for Salmonella enterica. All the study farms had at least one positive sample for Salmonella enterica (frequency range: 3-60%). Apparent prevalence at farm-level was therefore 100% (one-sided 97.5% confidence limit: 89%). Twenty-eight different serovars for Salmonella enterica were found. Based on increase the number of study districts, farms as well as animals in combination with improvement of sampling methods, possible spatial differences and risk factors/indicators should be clarified by further investigations.