Salmonella represents the most common group of bacteria to cause human food poisoning, according to USDA’s Food Safety and Inspection Service.

Pork producers want to reduce salmonella before their pigs enter the food chain. To help them achieve this goal, a team of Boehringer Ingelheim Vetmedica veterinary researchers, led by John Kolb, DVM, evaluated the effect of the company’s oral salmonella vaccine Enterisol SC-54, on post-harvest salmonella contamination of pig carcasses.

In the experiment, litters were randomly treated with the vaccine seven days before weaning, and diagnosticians and statisticians were blinded as to treatment groups, Kolb says.

At weaning, pigs were transported to a wean-to-finish barn. Non-vaccinates were placed on the upper deck, vaccinates on the lower deck. Upon arrival, treatment groups were randomly mixed within pens.

Pigs were tested near the time of marketing, and more than 89% were positive for salmonella infection by enzyme-linked immunosorbent assay, Kolb reports.

At harvest, 100 pigs were randomly selected and transported for three hours to a regional abbatoir, with each treatment loaded into separate compartments of cleaned and disinfected trailers. Pigs were unloaded and placed into washed and disinfected lairage pens. Both vaccinated and non-vaccinated groups were slaughtered during the plant’s first shift.

On the day of slaughter, the transport trailer, lairage and pig cavities were swabbed and lymph nodes collected. After overnight chilling, carcasses were swabbed at the jowl (shown above), midline and tailhead for indications of salmonella. All samples were shipped to the ISU-VDL after each day of sampling and tested for the organism.

The results indicated that no salmonella organisms were isolated from Enterisol SC-54 vaccinates, and the oral vaccine “significantly reduced post-harvest salmonella contamination in this infected barn and in transport, proving that vaccination can be a viable pork safety tool,” Kolb says.