References
Salmonella spp. in pigs: an update on diagnostics and control

Abstract
Salmonella spp. is an important topic for both human and animal health, particularly Salmonella enterica ser. Typhimurium including its monophasic strains. Salmonella is an increasing problem on pig farms and the bacteria are transmitted through breeding pyramids, and can spread rapidly due to the high number of subclinical cases. Therefore, diagnosis on farm is extremely important, ensuring sampling from all areas of the unit to gain the overall infection picture. Modern diagnostic techniques allow differentiation between field and vaccine strains which is extremely important when implementing a vaccination programme on the farm. Vaccination accompanied by hygiene and biosecurity measures make up the three pillars of Salmonella spp. control, each of which should be given equal attention. Vaccination has been shown to be very effective in reducing environmental pressure and therefore prevalence and clinical signs due to S. enterica ser. Typhimurium. Vaccination forms part of successful Salmonella spp. control, although it is important to remember that Salmonella spp. control requires a long-term approach using a combination of interventions and avoiding the long-term use of antimicrobial treatment.
Salmonella spp. is still the second most common zoonosis within the EU with over 91 000 cases reported in 2017 (European Food Safety Authority (EFSA), 2018). In pig meat, S. enterica ser. Typhimurium was the commonest reported serovar and accounted for 161 (27%) out of the 595 Salmonella spp. isolates serotyped. The group of monophasic variants of Salmonella Typhimurium was the commonest reported serovar from pigs and pig meat accounting for, respectively, 167 (37.4%) and 129 (22%) isolates. These results confirm that pigs are the main animal reservoir for monophasic variants of Salmonella Typhimurium. Farm animals are an important source of infections to humans, with risk of contamination of the food chain when infected animals are transported to slaughter facilities. Salmonella Typhimurium prevalence in UK and Irish herds in both breeding and slaughter pigs have historically been the highest in the EU, with figures of 19.4% and 17.5% respectively (EFSA, 2009) (Figure 1).
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