Balmer Sandra, Vögtlin Andrea, Thür Barbara, Büchi Martina, Abril Carlos, Houmard Matthias, Danuser Jürg, Schwermer Heinzpeter
Federal Food Safety and Veterinary Office FSVO, Schwarzenburgstrasse 155, CH-3003 Bern, Switzerland.
Institute of Virology and Immunology IVI, Sensemattstr. 293, CH-3147 Mittelhäusern, Switzerland.
Prev Vet Med. 2014 Oct 15;116(4):370-9. doi: 10.1016/j.prevetmed.2014.03.026. Epub 2014 Apr 5.
Infections with Schmallenberg virus (SBV), a novel Orthobunyavirus transmitted by biting midges, can cause abortions and malformations of newborns and severe symptoms in adults of domestic and wild ruminants. Understanding the temporal and spatial distribution of the virus in a certain territory is important for the control and prevention of the disease. In this study, seroprevalence of antibodies against SBV and the spatial spread of the virus was investigated in Swiss dairy cattle applying a milk serology technique on bulk milk samples. The seroprevalence in cattle herds was significantly higher in December 2012 (99.5%) compared to July 2012 (19.7%). This high between-herd seroprevalence in cattle herds was observed shortly after the first detection of viral infections. Milk samples originating from farms with seropositive animals taken in December 2012 (n=209; mean 160%) revealed significantly higher S/P% ratios than samples collected in July 2012 (n=48; mean 103.6%). This finding suggests a high within-herd seroprevalence in infected herds which makes testing of bulk tank milk samples for the identification farms with past exposures to SBV a sensitive method. It suggests also that within-herd transmission followed by seroconversion still occurred between July and December. In July 2012, positive bulk tank milk samples were mainly restricted to the western part of Switzerland whereas in December 2012, all samples except one were positive. A spatial analysis revealed a separation of regions with and without positive farms in July 2012 and no spatial clustering within the regions with positive farms. In contrast to the spatial dispersion of bluetongue virus, a virus that is also transmitted by Culicoides midges, in 2008 in Switzerland, the spread of SBV occurred from the western to the eastern part of the country. The dispersed incursion of SBV took place in the western part of Switzerland and the virus spread rapidly to the remaining territory. This spatial pattern is consistent with the hypothesis that transmission by Culicoides midges was the main way of spreading.
施马伦贝格病毒（SBV）是一种由叮咬蠓传播的新型正布尼亚病毒，其感染可导致家养和野生反刍动物的新生儿流产和畸形以及成年动物出现严重症状。了解病毒在某一地区的时空分布对于疾病的控制和预防至关重要。在本研究中，采用牛奶血清学技术对瑞士奶牛的散装牛奶样本进行检测，调查了抗SBV抗体的血清阳性率和病毒的空间传播情况。与2012年7月（19.7%）相比，2012年12月牛群中的血清阳性率显著更高（99.5%）。在首次检测到病毒感染后不久，就观察到牛群中这种较高的群体间血清阳性率。2012年12月采集的来自血清阳性动物农场的牛奶样本（n = 209；平均160%）显示，其S/P%比值显著高于2012年7月采集的样本（n = 48；平均103.6%）。这一发现表明，感染牛群中群体内血清阳性率较高，这使得检测散装牛奶样本以识别过去接触过SBV的农场成为一种敏感方法。这也表明，在7月至12月期间，群体内传播以及随后的血清转化仍在发生。2012年7月，阳性散装牛奶样本主要局限于瑞士西部，而2012年12月，除一个样本外，所有样本均为阳性。空间分析显示，2012年7月有阳性农场和无阳性农场的区域相互分离，且阳性农场所在区域内无空间聚集现象。与2008年在瑞士也由库蠓传播的蓝舌病毒的空间扩散情况相反SBV的传播是从该国西部向东部扩散。SBV的分散式入侵发生在瑞士西部，病毒迅速传播到其余地区。这种空间模式与库蠓传播是主要传播方式的假设一致。
