Observations on the distribution of Salmonella on primary pig breeding farms

Davies, Robert
McLaren, I.
Wales, A.
Bedford, S.
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Salmonella infection in pigs has emerged as an important potential public health issue in recent years and several countries have introduced monitoring and control programmes. However, the Salmonella status of most primary breeding herds remains unknown. This paper describes the results of intensive sampling carried out on four occupied primary pig breeding farms and one breeding farm which was purchased and cleaned and disinfected before being used for primary breeding. All premises were sampled intensively by taking large gauze swab samples from every pen of breeding sows, boars and rearing gilt and boar progeny. Samples of equipment and faeces plus carcases of wildlife vectors were also collected. On one farm (A) S. Derby, S. Kedougou and S. Newport were found in all locations whereas S. Typhimurium (DT1 04, DT20) was restricted to gilts retained for the herd and gilts and boars being reared for sale. There was considerable involvement of rodents and evidence of ineffective disinfection of farrowing crates. On a second farm (B), owned by the same company, there were similar findings, with S. Meleagridis also present. Improvements to rodent control but not disinfection produced no reduction in the overall prevalence of Salmonella. On two other farms, belonging to a separate company, S. Give predominated in adult breeding stock and rearing gilts and boars but some S. Typhimurium (OT1 04, DT193) was also present in the young stock on the larger unit (C). In the smaller unit (D), in which hygiene and rodent control was much better, only S. Give and S. Kedougou were found. In another farm (E) S. Stanley, S. Bredeney, S. Mbandaka and S. Typhimurium were found before total depopulation. Cleaning and disinfection was poor initially but successful after improvements, but no sampling was permitted in the new primary breeding herd by the new owners of the arm.