PDF(Pubmed)
Abstract：
BACKGROUND: Monitoring of infectious diseases on swine farms requires a high diagnostic sensitivity and specificity of the test system. Moreover, particularly in cases of swine influenza A virus (swIAV) it is desirable to include characterization of the virus as precisely as possible. This is indispensable for strategies concerning prophylaxis of swIAV and furthermore, to meet the requirements of a purposeful monitoring of newly emerging swIAV strains in terms of vaccine design and public health. Within the present cross-sectional study, we compared the diagnostic value of group samples (wipes of surfaces with direct contact to mouth/nose, dust wipes, udder skin wipes, oral fluids) to individual samples (nasal swabs, tracheobronchial swabs) for both swIAV identification and characterization. Sampling included different stages of pig production on 25 sow farms with attached nursery considered as enzootically infected with swIAV. Firstly, samples were analyzed for IAV genome and subsequently samples with Ct-values < 32 were subtyped by multiplex RT-qPCR.
RESULTS: Nasal swabs of suckling piglets and nursery pigs resulted in a higher odds to detect swIAV (p < 0.001) and to identify swIAV subtypes by RT-qPCR (p < 0.05) compared to nasal swabs of sows. In suckling piglets, significant higher rates of swIAV detection could be observed for nasal swabs (p = 0.007) and sow udder skin wipes (p = 0.036) compared to contact wipes. In the nursery, group sampling specimens were significantly more often swIAV positive compared to individual samples (p < 0.01), with exception of the comparison between contact wipes and nasal swabs (p = 0.181). However, in general nasal swabs were more likely to have Ct-value < 32 and thus, to be suitable for subtyping by RT-qPCR compared to dust wipes, contact wipes, udder skin wipes and tracheobronchial swabs (p < 0.05). Interestingly, different subtypes were found in different age groups as well as in different specimens in the same holding.
CONCLUSIONS: Although population-based specimens are highly effective for swIAV monitoring, nasal swabs are still the preferable sampling material for the surveillance of on-farm circulating strains due to significantly higher virus loads. Remarkably, sampling strategies should incorporate suckling piglets and different age groups within the nursery to cover as many as possible of the on-farm circulating strains.
RESULTS: Nasal swabs of suckling piglets and nursery pigs resulted in a higher odds to detect swIAV (p < 0.001) and to identify swIAV subtypes by RT-qPCR (p < 0.05) compared to nasal swabs of sows. In suckling piglets, significant higher rates of swIAV detection could be observed for nasal swabs (p = 0.007) and sow udder skin wipes (p = 0.036) compared to contact wipes. In the nursery, group sampling specimens were significantly more often swIAV positive compared to individual samples (p < 0.01), with exception of the comparison between contact wipes and nasal swabs (p = 0.181). However, in general nasal swabs were more likely to have Ct-value < 32 and thus, to be suitable for subtyping by RT-qPCR compared to dust wipes, contact wipes, udder skin wipes and tracheobronchial swabs (p < 0.05). Interestingly, different subtypes were found in different age groups as well as in different specimens in the same holding.
CONCLUSIONS: Although population-based specimens are highly effective for swIAV monitoring, nasal swabs are still the preferable sampling material for the surveillance of on-farm circulating strains due to significantly higher virus loads. Remarkably, sampling strategies should incorporate suckling piglets and different age groups within the nursery to cover as many as possible of the on-farm circulating strains.
摘要：
背景：监测猪场的传染病需要测试系统的高诊断灵敏度和特异性。此外，特别是在猪甲型流感病毒(swIAV)的情况下,期望尽可能精确地包括病毒的表征。这对于预防swIAV的策略是必不可少的，此外，在疫苗设计和公共卫生方面满足有目的地监测新出现的SwIAV毒株的要求。在目前的横断面研究中，我们比较了组样本的诊断价值(直接接触口/鼻的表面擦拭物，防尘湿巾,乳房皮肤湿巾，口腔液)到单个样本(鼻拭子，气管支气管拭子）用于SwIAV鉴定和表征。采样包括25个母猪养殖场的养猪生产的不同阶段，这些母猪养殖场被认为是对SwIAV的植物性感染。首先,分析样品的IAV基因组,随后通过多重RT-qPCR对Ct值<32的样品进行亚分型。
结果：与母猪的鼻拭子相比，乳猪和保育猪的鼻拭子检测swIAV（p<0.001）和通过RT-qPCR鉴定swIAV亚型（p<0.05）的几率更高。在哺乳仔猪中，与接触湿巾相比，鼻拭子（p=0.007）和母猪乳房皮肤湿巾（p=0.036）的swIAV检测率明显更高。在托儿所，与单个样本相比，整群抽样样本明显更容易出现swIAV阳性（p<0.01），除了接触湿巾和鼻拭子之间的比较（p=0.181）。然而,一般来说，鼻拭子更有可能具有<32的Ct值，因此，与防尘湿巾相比，适合通过RT-qPCR进行分型，接触湿巾,乳房皮肤湿巾和气管支气管拭子（p<0.05）。有趣的是,不同的亚型在不同的年龄组，以及在不同的标本在同一持有。
结论：尽管基于人群的样本对于SwIAV监测非常有效，由于病毒载量明显较高,鼻拭子仍然是监测农场流行毒株的首选取样材料.值得注意的是,采样策略应将哺乳仔猪和不同年龄段的仔猪纳入苗圃中，以覆盖尽可能多的农场循环菌株。
结果：与母猪的鼻拭子相比，乳猪和保育猪的鼻拭子检测swIAV（p<0.001）和通过RT-qPCR鉴定swIAV亚型（p<0.05）的几率更高。在哺乳仔猪中，与接触湿巾相比，鼻拭子（p=0.007）和母猪乳房皮肤湿巾（p=0.036）的swIAV检测率明显更高。在托儿所，与单个样本相比，整群抽样样本明显更容易出现swIAV阳性（p<0.01），除了接触湿巾和鼻拭子之间的比较（p=0.181）。然而,一般来说，鼻拭子更有可能具有<32的Ct值，因此，与防尘湿巾相比，适合通过RT-qPCR进行分型，接触湿巾,乳房皮肤湿巾和气管支气管拭子（p<0.05）。有趣的是,不同的亚型在不同的年龄组，以及在不同的标本在同一持有。
结论：尽管基于人群的样本对于SwIAV监测非常有效，由于病毒载量明显较高,鼻拭子仍然是监测农场流行毒株的首选取样材料.值得注意的是,采样策略应将哺乳仔猪和不同年龄段的仔猪纳入苗圃中，以覆盖尽可能多的农场循环菌株。
