Stadler Julia, Zwickl Sophia, Gumbert Sophie, Ritzmann Mathias, Lillie-Jaschniski Kathrin, Harder Timm, Graaf-Rau Annika, Skampardonis Vassilis, Eddicks Matthias
Clinic for Swine, Centre for Clinical Veterinary Medicine, Ludwig-Maximilians-Universität München, Oberschleißheim, Germany.
CEVA Tiergesundheit, Duesseldorf,, Germany.
Porcine Health Manag. 2024 May 19;10(1):19. doi: 10.1186/s40813-024-00367-9.
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.
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.
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.
猪场传染病监测需要检测系统具有高诊断敏感性和特异性。此外，特别是对于甲型猪流感病毒（swIAV），尽可能精确地对病毒进行特征鉴定是很有必要的。这对于swIAV的预防策略不可或缺，而且对于在疫苗设计和公共卫生方面有针对性地监测新出现的swIAV毒株的要求来说也是必不可少的。在本横断面研究中，我们比较了用于swIAV鉴定和特征鉴定的群体样本（直接接触口鼻的表面擦拭物、灰尘擦拭物、乳房皮肤擦拭物、口腔液体）和个体样本（鼻拭子、气管支气管拭子）的诊断价值。采样涵盖了25个被认为存在swIAV地方流行感染的母猪场及其附属保育舍的生猪生产不同阶段。首先，对样本进行IAV基因组分析，随后对Ct值<32的样本通过多重RT-qPCR进行亚型鉴定。
与母猪鼻拭子相比，哺乳仔猪和保育猪的鼻拭子检测到swIAV的几率更高（p<0.001），并且通过RT-qPCR鉴定swIAV亚型的几率更高（p<0.05）。在哺乳仔猪中，与接触擦拭物相比，鼻拭子（p=0.007）和母猪乳房皮肤擦拭物（p=0.036）检测到swIAV的比率显著更高。在保育舍中，与个体样本相比，群体采样标本的swIAV阳性率显著更高（p<0.01），接触擦拭物与鼻拭子的比较除外（p=0.181）。然而，一般来说，与灰尘擦拭物、接触擦拭物、乳房皮肤擦拭物和气管支气管拭子相比，鼻拭子的Ct值更有可能<32，因此更适合通过RT-qPCR进行亚型鉴定（p<0.05）。有趣的是，在不同年龄组以及同一养殖场的不同样本中发现了不同的亚型。
尽管群体样本对于swIAV监测非常有效，但由于病毒载量显著更高，鼻拭子仍然是监测猪场流行毒株的首选采样材料。值得注意的是，采样策略应纳入哺乳仔猪和保育舍内的不同年龄组，以涵盖尽可能多的猪场流行毒株。
