Low prevalence of Salmonella enterica in cull dairy cattle at slaughter in Northern Italy

Abstract

In order to evaluate <em>Salmonella</em> carrier status of cull dairy cattle at slaughter, 125 animals were randomly selected during the period February-May 2016. Dairy cows were reared in 89 farms located in two regions of Northern Italy (Lombardy and Emilia-Romagna regions), where bovine milk is primarily used for <em>Parmigiano- Reggiano</em> cheese and <em>Grana Padano</em> cheese production. Samples were collected by swabbing a 400-cm² area of the brisket hide and by rectoanal mucosal swabs. They were tested following the reference ISO 6579 method and the isolates were serotyped following the Kauffmann-White-Le Minor scheme and genotyped by <em>Xba</em>I PFGE. <em>Salmonella</em> was detected in 1.6% of the brisket hide samples (2/125) (95% CI: 0.4-5.6) and never found in faecal samples (95% CI: 0-3%). The positive cattle were reared in two farms located only in Emilia- Romagna region. The isolates were typed as <em>S.</em> Derby and <em>S.</em> Seftenberg. The comparison of the pulsed-field gel electrophoresis (PFGE) patterns of the bovine strains with all the PFGE patterns of the same serotypes responsible for human salmonellosis cases notified in Emilia-Romagna region in the years 2013-2015 did not find any correspondence. Therefore, the role of cull dairy cattle in transmitting <em>Salmonella</em> to humans seems to be less important than those of pigs and poultry in EU, but more data are needed for completing attribution source studies.