Sock and Environmental Swabs as an Efficient, Non-Invasive Tool to Assess the Salmonella Status of Sow Farms

SIMPLE SUMMARY: Salmonella is an important pathogen in both livestock and humans, therefore much research has been conducted aiming to improve control methods and consequently reduce prevalence. Salmonella monitoring systems have been implemented in swine slaughter plants across Germany to test meat juices or blood of finisher animals being processed. The farms are placed into categories according to the level of Salmonella positivity, which then dictate actions required to be taken by the farmer as well as any price penalties applied to the meat sold. Since the implementation of this monitoring system, the distribution of farms across categories has not drastically altered, indicating that the national Salmonella situation is not necessarily improving. More action seems to be required at the breeding and multiplying levels of production rather than simply monitoring the finisher farms. Improving the diagnostic methods at these early stages of production in sows and nursery pigs, and consequently the control of Salmonella, would aid improvement of the Salmonella situation across the whole pig stock across Germany, including finishing farms. Sock and swab sampling has been demonstrated as a simple, cheap and effective sampling method for other enteric pathogens and therefore may be a useful tool for the diagnosis of Salmonella on swine farms. Availability of an easily accessible diagnostic method for Salmonella may increase investigations into the pathogen on sow farms and consequently improve the control methods implemented and reduce Salmonella positivity at slaughter. ABSTRACT: Salmonellosis is the second most reported gastrointestinal infection in humans after campylobacteriosis and a common cause of foodborne outbreaks in the European Union (EU). In addition to consumption of contaminated animal-based foods, such as poultry, beef and eggs, pork is an important source of human salmonellosis outbreaks; therefore, Salmonella (S.) control should start in the early stages of pig production. To be able to implement effective control measures to reduce the risk of pigs being infected by Salmonella, it is important to identify the serovars circulating on farm within the different stages of production, including as early as sow and piglet breeding. The aim of the present study was to assess the Salmonella status of sow farms either producing their own finishers or delivering piglets to fattening farms with a known high serological prevalence identified within the QS Salmonella monitoring system. Overall, 97 (92.4%) of 105 investigated piglet-producing farms across Germany tested positive in at least one sample. Salmonella was detected in 38.2% of the sock and 27.1% of the environmental swab samples. S. Typhimurium was the most frequent serovar. In conclusion, sock and environmental swab samples are well suited for non-invasive Salmonella detection in different production units in farrowing farms. To establish a holistic Salmonella control program, all age classes of pig production should be sampled to enable intervention and implementation of countermeasures at an early stage if necessary.