Foddai Alessandro, Stockmarr Anders, Boklund Anette
Section of Epidemiology, National Veterinary Institute, Technical University of Denmark, Bülowsvej 27, DK-1870, Frederiksberg C, Denmark.
Statistics and Data Analysis Section, Department of Applied Mathematics and Computer Science, Technical University of Denmark, Matematiktorvet, DK-2800, Lyngby, Denmark.
BMC Vet Res. 2016 Jun 21;12(1):118. doi: 10.1186/s12917-016-0744-2.
The temporal sensitivity of the surveillance system (TemSSe) for Bovine Viral Diarrhea (BVD) in Danish dairy herds was evaluated. Currently, the Danish antibody blocking ELISA is used to test quarterly bulk tank milk (BTM). To optimize the surveillance system as an early warning system, we considered the possibility of using the SVANOVIR ELISA, as this test has been shown to detect BVD-positive herds earlier than the blocking ELISA in BTM tests. Information from data (2010) and outputs from two published stochastic models were fed into a stochastic scenario tree to estimate the TemSSe. For that purpose we considered: the risk of BVD introduction into the dairy population, the ELISA used and the high risk period (HRP) from BVD introduction to testing (at 90 or 365 days). The effect of introducing one persistently infected (PI) calf or one transiently infected (TI) milking cow into 1 (or 8) dairy herd(s) was investigated. Additionally we estimated the confidence in low (PLow) herd prevalence (<8/4109 infected herds) and the confidence in complete freedom (PFree) from BVD (< 1/4109).
The TemSSe, the PLow, and the PFree were higher, when tests were performed 365 days after BVD introduction, than after 90 days. Estimates were usually higher for the SVANOVIR than for the blocking ELISA, and when a PI rather than a TI was introduced into the herd(s). For instance, with the current system, the median TemSSe was 64.5 %, 90 days after a PI calf was introduced into eight dairy herds. The related median PLow was 72.5 %. When a PI calf was introduced into one herd the median TemSSe was 12.1 %, while the related PFree was 51.6 %. With the SVANOVIR ELISA these estimates were 99.0 %; 98.9 %, 43.7 % and 62.4 %, respectively.
The replacement of the blocking ELISA with the SVANOVIR could increase the TemSSe, the PLow and PFree remarkably. Those results could be used to optimize the Danish BVD surveillance system. Furthermore, the approach proposed in this study, for including the effect of the HRP within the scenario tree methodology, could be applied to optimize early warning surveillance systems of different animal diseases.
对丹麦奶牛群中牛病毒性腹泻（BVD）监测系统的时间敏感性（TemSSe）进行了评估。目前，丹麦抗体阻断ELISA用于每季度检测一次散装罐牛奶（BTM）。为了将监测系统优化为早期预警系统，我们考虑了使用SVANOVIR ELISA的可能性，因为在BTM检测中，该检测已被证明比阻断ELISA能更早地检测出BVD阳性牛群。将数据（2010年）信息和两个已发表的随机模型的输出结果输入到一个随机情景树中，以估计TemSSe。为此，我们考虑了：BVD传入奶牛群体的风险、所使用的ELISA以及从BVD传入到检测（90天或365天）的高风险期（HRP）。研究了向1个（或8个）奶牛群引入1头持续感染（PI）犊牛或1头短暂感染（TI）泌乳奶牛的影响。此外，我们估计了对低群体流行率（PLow）（<8/4109个感染牛群）的置信度以及对BVD完全无感染（PFree）（<1/4109）的置信度。
在BVD传入365天后进行检测时，TemSSe、PLow和PFree高于传入90天后。通常，SVANOVIR的估计值高于阻断ELISA，并且当向牛群引入PI而非TI时。例如，在当前系统下，将1头PI犊牛引入8个奶牛群90天后，TemSSe中位数为64.5%。相关的PLow中位数为72.5%。当将1头PI犊牛引入1个牛群时，TemSSe中位数为12.1%，而相关的PFree为51.6%。使用SVANOVIR ELISA时，这些估计值分别为99.0%、98.9%、43.7%和62.4%。
用SVANOVIR取代阻断ELISA可显著提高TemSSe、PLow和PFree。这些结果可用于优化丹麦的BVD监测系统。此外，本研究中提出的将HRP的影响纳入情景树方法的途径，可应用于优化不同动物疾病的早期预警监测系统。
