Distribution of Salmonella in swine herds in Quebec

Five porcine finishing units, previously identified as contaminated by Salm onella, were sampled to identify possible sources of contamination and to s tudy the distribution of Salmonella within the herds. A total of 208 enviro nmental samples were taken and 87 samples (42%) were found contaminated by Salmonella spp. Salmonella was recovered from several types of samples. Amo ng these, fecal material from pens, building environment such as doors, flo ors, ventilation units, dust and farm accessories were most often found pos itive. Some of the flies and rodents were also positive. Two of the finishi ng units were part of an integrated production system and the prevalence an d distribution of Salmonella spp. at different production steps of the inte grated facilities were studied. Forty-one farms were sampled and a total of 1923 faecal samples in randomly selected pens were analysed. One hundred a nd fifty-one samples (7.9%) were positive for Salmonella spp. Among the far ms sampled, 70.7% (29/41) were positive for isolation of Salmonella. The di fferent levels in the integrated production were unevenly contaminated. Rep lacement sow (15.9%) and finishing unit for gilts (21.9%) were the most con taminated levels. Ten serotypes of Salmonella (n = 132) were identified in the production pyramid with a predominance of Salmonella Derby (37.1%) and Salmonella Typhimurium (34.1%). Pulse Field Gel Electrophoresis analysis of the various isolates from serotypes and Salmonella Typhimurium, Salmonella Derby and Salmonella Anatum showed no variation in the genetic profiles, w ithin each serotype, suggesting a vertical contamination throughout the dif ferent production steps. (C) 1999 Elsevier Science B.V. All rights reserved .