Results of a study suggest that Salmonella prevalence in pigs at slaughter in the United Kingdom did not change much from 2013 to 2019.

Findings are from an abattoir-based survey that sampled cecal contents pigs in nine British pig abattoirs during 2019. The cecum is at the start of the large intestine.

Salmonella was isolated from 112 of 348 samples collected at slaughter from animals at 286 farms; a prevalence of 32.2 percent. Most pigs came from farms in England with some from Scotland and Wales, according to the study published in the journal Epidemiology and Infection.

Twelve different Salmonella serovars were isolated, with the most common being Salmonella 4,[5],12:i:-, a monophasic variant of Salmonella Typhimurium, followed by Salmonella Derby. Salmonella Ohio and Salmonella Kedougou were only found in a single sample each.

Similar results to 2013
Industry has tried measures to control Salmonella in pig herds, through increased biosecurity, improved cleaning and disinfection, use of organic acids and vaccination.

There was no significant change compared to the overall prevalence of 30.5 percent in the last abattoir survey in the UK in 2013.

There was also no major difference in Salmonella isolation from the cecal samples collected at each of the nine abattoirs.

Cecal samples were collected during 12 months, with between 19 and 38 tested each month. Month-to-month variations in positive samples were seen with peaks in Salmonella isolated from cecal contents in February, March and October.

“Continuing surveillance at slaughter is recommended to assess impacts of farm-based and abattoir-based interventions and to monitor potential public health risk associated with consumption of Salmonella-contaminated pork products,” said researchers.

Difference between types of swabs
In 2019, of the 3,785 carcasses tested in the UK, 1.72 percent were Salmonella positive. This was down from 2018, when 2.87 percent of 3,839 carcasses were positive. These samples were taken by food businesses and tested in private laboratories.

Carcass swabs provide an indication of Salmonella contamination on the pig after the slaughter process, and is a better marker for the risk to public health.

Pigs arriving at slaughter normally have higher Salmonella prevalence than at the farm. This is because they might restart shedding after being exposed to stressful events such as transport or because of new contamination and infection during transit or at the abattoir.

Slaughter hygiene practices contribute to the prevalence of pork carcass contamination, and a significant difference between Salmonella prevalence in cecal contents and carcass swabs is to be expected, according to the research.