Abstract
BackgroundThe prevalence of Salmonella in food producing animals is very low in Sweden due to rigorous control programmes. However, no active surveillance is in place in sheep. The authorities decided to perform a prevalence study in sheep herds because findings at slaughter indicated that sheep associated S. diarizonae (S. enterica subspecies diarizonae serovar 61:(k):1, 5, (7)) might be common in sheep. Sampling was stratified by herd size in two groups, small herds with ≤ 30 animals and large herds with > 30 animals. In each stratum, 237 herds were selected at random. Faecal samples received from 244 out of the 474 randomly selected herds were analysed.ResultsA total of 40 of 100 (40%) of large herds and 17 of 144 (12%) of small herds were positive. The overall adjusted prevalence was 17.6% (95% CI, 12.9-22.2). Sheep associated S. diarizonae was detected in all counties (n = 21). Scientific opinions and an evaluation of on-farm control measures performed concluded that the impact of sheep associated S. diarizonae on human health is very low, and that risk management measures applied in response to findings of sheep associated S. diarizonae in sheep or sheep meat can be expected to have very little impact on reducing risks to human health. As a result, Swedish authorities decided to make an exemption for sheep associated Salmonella diarizonae in sheep and sheep meat in the current Salmonella control measures.ConclusionsSheep associated S. diarizonae is endemic in Swedish sheep herds. It is more common in large herds and not limited to certain parts of the country. The responsible authorities concluded that current risk management actions regarding sheep associated S. diarizonae in sheep and sheep meat are not proportional to the risk. This is the first time in the history of the Swedish Salmonella control programme that an exemption from the legislation has been made for a specific serovar. If there is any future indication of an increasing risk, due to e.g. change in the pathogenicity or development of antimicrobial resistance, the risk assessment will be re-evaluated and control measures reinforced if needed.
Highlights
The prevalence of Salmonella in food producing animals is very low in Sweden due to rigorous control programmes
The aim of the present paper is to describe the prevalence study conducted during the winter 2012 and the actions taken by authorities due to the result of the study
The responsible authorities concluded that current risk management actions regarding sheep associated S. diarizonae (SASd) in sheep and sheep meat are not proportional to the risk
Summary
The prevalence of Salmonella in food producing animals is very low in Sweden due to rigorous control programmes. The authorities decided to perform a prevalence study in sheep herds because findings at slaughter indicated that sheep associated S. diarizonae (S. enterica subspecies diarizonae serovar 61:(k): , (7)) might be common in sheep. Faecal samples received from 244 out of the 474 randomly selected herds were analysed. Bacteria of the species Salmonella enterica occur worldwide and are a common cause of gastro-intestinal infections in both humans and animals. Bacteria belonging to S. enterica are divided into six subspecies consisting of more than 2,500 different serovars [1]. S. enterica subspecies diarizonae serovar 61:(k): , (7). The bacteria have been reported to be commonly found in sheep in the United Kingdom (UK), Norway and Switzerland [5,6,7,8]. SASd is only occasionally isolated from other species [12] and seldom reported in humans. In the UK two human cases were reported during the time period 1966–1990, in the USA, 27 cases were reported between
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