Bacteriological evaluation of vaccination against Salmonella Typhimurium with an attenuated vaccine in subclinically infected pig herds.

anglais. peer reviewed

anglais. Subclinical infections withSalmonellaTyphimurium occur frequently in pigs. They constitute a risk for humansalmonellosis and are difficult to control with currently available control measures. Vaccination againstSalmonellaTyphimurium in pigs can be an effective tool to controlSalmonellainfections at farm level.In the present study, the efficacy of an attenuatedSalmonellaTyphimurium vaccine (Salmoporc®, IDTBiologika) to controlSalmonellainfections in pigs was evaluated in three subclinically infected pig herds. Theeffect onSalmonellaexcretion and the number of pigs positive forSalmonellaTyphimurium field and vaccinestrains in ileocecal lymph nodes at slaughter were evaluated using five different vaccination strategies: 1.vaccination of sows, 2. vaccination of sows and piglets, 3. vaccination of sows and fattening pigs, 4. vaccinationof piglets, 5. vaccination of fattening pigs, which were all compared to a non-vaccinated control group (ex-perimental group 6). Each vaccination strategy was implemented in each farm, during two consecutive pro-duction cycles of the same sows.The prevalence ofSalmonellaTyphimurium field strain excretion was low; in total, 4% of the fecal andovershoe samples collected in the non-vaccinated control group wereSalmonellaTyphimurium field strain po-sitive. The excretion ofSalmonellaTyphimurium field strain did not significantly differ between farms, pro-duction cycles and experimental groups. Applying vaccination in either sows and piglets, sows and fatteningpigs, or in piglets only, resulted in a significantly reduced number ofSalmonellaTyphimurium field strain po-sitive lymph nodes of slaughter pigs in the second production cycle, but not in the first production cycle.Vaccination of sows and piglets resulted in the most consistent reduction ofSalmonellaTyphimurium field strainpositive lymph nodes at slaughter. The vaccine strain was detected in the lymph nodes of 13 pigs at slaughter,indicating the possible persistence of the vaccine strain until slaughter.Because of limitations in the study design, and the variability between farms and production cycles, theresults of the current observational study should be extrapolated with care. Nevertheless, the results provideevidence that applying vaccination againstSalmonellaTyphimurium in sows and piglets (preferred), sows andfattening pigs, and piglets only can support the control ofSalmonellaTyphimurium infections by decreasing theprevalence ofSalmonellaTyphimurium field strain positive lymph nodes at slaughter