HERD PREVALENCE OF SALMONELLA-ENTERICA INFECTIONS IN DANISH SLAUGHTERPIGS DETERMINED BY MICROBIOLOGICAL TESTING

As a part of a nationwide programme to survey and control salmonella i n pig herds, a microbiological survey of 1363 pig herds was performed in Denmark. A total of 13 468 slaughter pigs were examined at slaughte r by culture of 5 g of caecal contents. Overall, 30 different serotype s of Salmonella enterica were isolated from 832 pigs (6.2%). The predo minant serotype was S. Typhimurium, comprising 536 (64.4%) of the isol ates. Four hundred and forty-eight isolates of S. Typhimurium were exa mined by phage typing, resulting in detection of 17 different phage ty pes (definitive types, DT) with DT12 being the most frequent (49.1%). Salmonella enterica was found in 302 herds (22.2%), S. Typhimurium was found in 61.1% of these. 279 (23.1%) large herds (producing more than 2600 slaughter pigs per year) were found to be salmonella positive co mpared with 23 (14.7 %) small herds (annual production of 500 to 550 s laughter pigs). Practical constraints in the study design did not allo w for a firm conclusion on the interplay among herd size, geographical location and occurrence of salmonella. In 284 of 302 infected herds ( 94.0%) only one serotype was detected, Infections with two different s erovars were seen in 18 herds (6.0%).