Salmonella status in swine units characterization: comparative study of serology and bacteriology

Salmonella are the main cause of human collective food toxi-infections. A new European regulation published in November 2003 imposes to set up a control of these bacteria in the swine industry. Detection of asymptomatic pigs carrying Salmonella and a specific slaughtering process should reduce contamination of pork products. The interest of a serological method compared with the bacteriological method to evaluate levels of Salmonella in swine herds was investigated in 2,000 pigs. Five batches of 20 pigs stemming from 20 finishing pig herds were tested. Caecal contents were analysed with a bacteriological method and meat juice samples with a serological test. The concordance between these two methods was low at the individual level and moderate at the batch level. The instability of the serological and bacteriological status of the herds was also established. An effect of waiting time at slaughterhouse on bacteriological results was observed. Finally, this survey highlighted a clear influence of dry feeding on bacteriological and serological results.