Abstract
Simple SummarySalmonella is one of the most important bacterial zoonotic pathogens worldwide that can lead to infections in humans, particularly through the consumption of contaminated food. The percentage of diarrhoeal diseases attributable to the consumption of pork products has risen in recent years, whereas cases associated with poultry meat have considerably decreased. In the present study, the Salmonella prevalence on piglet-producing farms was determined on the basis of environmental samples and blood samples on 24 pig farms previously classified as Salmonella-inconspicuous (SI) and Salmonella-conspicuous (SC). In addition, the effects of sow vaccination against Salmonella prevalence in piglets on SC farms were investigated. The evaluation confirmed the previous classification into SC and SI farms—SC-farms showed significantly higher Salmonella prevalence in environmental samples and significantly higher OD% values in blood samples from piglets. Furthermore, vaccination of sows on SC farms was accompanied by the highest Salmonella prevalence in the environment, and by the highest antibody titer values in piglets, and therefore cannot influence the Salmonella prevalence solely at the farm level.Due to the zoonotic potential of Salmonella, the high prevalence of Salmonella on pig farms deserves particular attention. Because there is limited precise data on piglet-producing farms, this survey evaluated the Salmonella status of 24 different pig farms that had previously been divided into 12 Salmonella-conspicuous (SC) and 12 Salmonella-inconspicuous (SI) farms on the basis of the serological status of their piglets (25 kg). The evaluation was based on 498 environmental samples and 2641 blood samples, as well as on a biosecurity screening. SC farms were subdivided into farms with sow vaccination against Salmonella (n = 3) and those without vaccination (n = 9). In accordance with the previous classification, both the highest Salmonella prevalence in the environment and the highest antibody titers of the examined piglets were determined on SC farms at both defined time points. Piglets from vaccinated sows showed the highest OD% values, before and after vaccination. On SC farms, most Salmonella-positive samples could be obtained in rearing areas (2017: 40.8%, 2019: 26.0%). The results of this study indicate that sow vaccination alone cannot influence Salmonella prevalence at the farm level. Above all, general infection pressure seems to play a major role for Salmonella prevalence in the environment and for high OD% values of related pigs.
Highlights
Salmonella is one of the most important bacterial zoonotic and coincident food-borne pathogens worldwide and one of the main causes of food-borne diseases in humans, especially caused by the serovars Salmonella enteritidis and Salmonella typhimurium [1,2]
The evaluation of environmental samples in the present study showed a significantly higher prevalence of Salmonella in the environment of SC farms, especially in rearing areas despite increased biosecurity measures
Salmonella prevalence compared to the investigated SI farms
Summary
Salmonella is one of the most important bacterial zoonotic and coincident food-borne pathogens worldwide and one of the main causes of food-borne diseases in humans, especially caused by the serovars Salmonella enteritidis and Salmonella typhimurium [1,2]. Due to the demonstrated high correlations between Salmonella prevalence on pig farms and carcass contamination, control mechanisms at the farm level are of major importance [5,6]. As some studies have already identified the acquisition of asymptomatic carriers as the main source of Salmonella in herds [8,9,10], and no related monitoring programmes have involved the piglet producers so far, there is a need to investigate appropriate approaches to reducing cases of Salmonella already in piglet rearing at the beginning of the chain [11,12]. Vaccines can be used to control clinical diseases whereby in modern pig production, vaccination is mainly used to reduce infection pressure by suppressing the shedding of Salmonella [14]. Salmonella prevalence on piglet-producing farms was investigated using blood samples and environmental samples with regard to distribution on the farm, compliance with previous classification into Salmonella-inconspicuous and Salmonella-conspicuous farms, as well as effects of sow immunisation on Salmonella prevalence in environmental samples and on optical density (OD%) values of the piglets
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