Austrian Agency for Health and Food Safety (AGES), Institute for Veterinary Disease Control Linz, Austria.
University Clinic for Ruminants, Department for Farm Animals and Veterinary Public Health, University of Veterinary Medicine Vienna, Austria.
Prev Vet Med. 2024 Sep;230:106277. doi: 10.1016/j.prevetmed.2024.106277. Epub 2024 Jul 5.
Due to its increasing occurrence in cattle farms in various countries, leading to significant economic losses in affected livestock, Salmonella enterica subspecies enterica serovar Dublin (S. Dublin) has become a highly investigated pathogen in cattle production. In Austria, there have been occasional human cases of S. Dublin as well as an increase in laboratory-confirmed cases in cattle, indicating the need for a screening programme to determine the current status in Austria. The aims of this study were, firstly, to determine the seroprevalence of S. Dublin in dairy herds through bulk milk screenings in two federal states (Salzburg, Tyrol) of Austria. Secondly, the study aimed to identify the infection status of the herds through individual animal and herd level detection, comparing microbiological, molecular and serological detection methods. The results of the study will allow the development of a sampling strategy for a surveillance programme in Austria. A total of 6973 dairy farms were tested through serological bulk milk screening. The seroprevalence for the federal state of Tyrol was 14.8 % and for Salzburg it was 18.2 %, resulting in an average seroprevalence of 16.5 %. At an individual animal level, 205 (11.3 %) animals tested positive for shedding of S. Dublin in the faeces through microbiological detection, and 268 (17.0 %) animals had positive values (ct value ≤ 38) by qPCR. The association between microbiological and molecular detection was statistically significant (p < 0.001), with a calculated kappa value of 0.65 ± 0.27 (p ≤ 0.001), assuming a substantial level of agreement. In 17 herds, where an individual animal tested positive for shedding of S. Dublin, environmental sampling and testing were carried out. At a herd level 16 (94.1 %) out of the 17 participating herds, tested positive for S. Dublin either microbiologically or by molecular assay in boot swab samples. Bulk milk samples from 14 out of the 17 participating herds were analysed for antibodies to S. Dublin and 12 samples (85.7 %) were positive. In total 111 (18.9 %) out of 587 blood samples tested positive for S. Dublin antibodies, demonstrating a statistically significant correlation (p < 0.001) both with microbiological (κ = 0.32 ± 0.49; p ≤ 0.001) and molecular (κ=0.23 ± 0.06; p ≤ 0.001) findings. It was possible to identify S. Dublin by culture from boot swabs in 14 (82.4 %) out of 17 herds and by molecular assay using qPCR in 15 (88.2 %) out of 17 herds, indicating a suitable sample type for screening on a herd level-basis for acute infections, but not for identifying chronic infections or asymptomatic carriers. Other environmental samples, such as sponge-sticks, are only suitable to a limited extent for the detection of S. Dublin. The results of this study demonstrate a moderate S. Dublin prevalence in dairy herds in the selected Austrian regions, signalling further screening and management programmes for the future.
由于其在各国奶牛场的发病率不断上升,给受感染的牲畜造成了重大的经济损失,因此,都柏林沙门氏菌亚种都柏林血清型(S. Dublin)已成为牛群生产中研究的重点病原体。在奥地利,曾偶尔有人类感染 S. Dublin 的病例,以及实验室确诊病例在牛群中有所增加,这表明需要开展一项筛查计划来确定奥地利目前的情况。本研究的目的首先是通过对奥地利两个联邦州(萨尔茨堡州、蒂罗尔州)的牛奶进行批量筛选,确定都柏林沙门氏菌在奶牛群中的血清流行率。其次,该研究旨在通过个体动物和畜群水平的检测,比较微生物学、分子和血清学检测方法,确定畜群的感染状况。该研究的结果将有助于制定奥地利监测计划的抽样策略。共对 6973 个奶牛场进行了血清学批量牛奶筛选。蒂罗尔州的血清流行率为 14.8%,萨尔茨堡州为 18.2%,平均血清流行率为 16.5%。在个体动物水平上,通过微生物检测在粪便中检测到 205 头(11.3%)动物有 S. Dublin 脱落,通过 qPCR 检测到 268 头(17.0%)动物的阳性值(ct 值≤38)。微生物学和分子检测之间的关联具有统计学意义(p<0.001),假设一致性程度较高,计算得到的kappa 值为 0.65±0.27(p<0.001)。在 17 个个体动物检测到 S. Dublin 脱落的畜群中,进行了环境采样和检测。在 17 个参与的畜群中,有 16 个(94.1%)在靴拭子样本中通过微生物学或分子检测呈 S. Dublin 阳性。对 17 个参与畜群中的 14 个畜群的牛奶样本进行了都柏林沙门氏菌抗体分析,其中 12 个样本(85.7%)为阳性。总共从 587 份血液样本中检测到 111 份(18.9%)对 S. Dublin 抗体呈阳性,表明与微生物学(κ=0.32±0.49;p≤0.001)和分子(κ=0.23±0.06;p≤0.001)检测结果均存在统计学显著相关性。通过从靴拭子中培养的方法在 17 个畜群中的 14 个(82.4%)中可以鉴定出 S. Dublin,通过使用 qPCR 的分子检测在 17 个畜群中的 15 个(88.2%)中可以鉴定出 S. Dublin,表明在畜群水平上进行急性感染的筛查,靴拭子是一种合适的样本类型,但不能用于鉴定慢性感染或无症状携带者。其他环境样本,如海绵棒,仅在一定程度上适合检测 S. Dublin。本研究的结果表明,在所选的奥地利地区的奶牛群中,都柏林沙门氏菌的流行率适中,表明未来需要进一步开展筛查和管理计划。