Golender Natalia, Eldar Avi, Ehrlich Marcelo, Kenigswald Gabriel, Shlamovitz Ily, Even-Tov Boris, Zamir Lior, Klement Eyal, Bumbarov Velizar
Division of Virology, Kimron Veterinary Institute, Beit Dagan 5025001, Israel.
Koret School of Veterinary Medicine, The Robert H. Smith Faculty of Agriculture, Food & Environment, The Hebrew University of Jerusalem, Rehovot 7628604, Israel.
Microorganisms. 2021 Sep 14;9(9):1955. doi: 10.3390/microorganisms9091955.
Outbreaks of the European Bluetongue virus (BTV) serotype 8 (BTV-8), which are characterized by activity cycles separated by years of inactivity, may be influenced by genetic changes of the virus or by herd immunity. BTV activity in Israel is characterized by similar dynamics, but differs from European countries in its vector population, environmental conditions, and lack of cattle vaccination against this serotype. Comparison of these two geographical systems and characterization of their epidemiological connection is therefore of high interest in-order to better understand the factors influencing BTV-8 evolution. BTV-8, closely related to the European strain, was introduced to Israel in 2008. It was at the center of BT outbreaks in 2010 and 2015-2016 and thereafter was lastly isolated in Israel in 2019. We performed genetic analyses of twelve BTV-8 Israeli strains isolated between 2008 and 2019 and compared them with published sequences of BTV-8 isolated in other countries. The analysis revealed a single introduction of BTV-8 into Israel and thereafter extensive occurrence of genomic drifts and multiple reassortments with local BTV strains. Comparison of the Israeli and Cypriot BTV-8 from 2015 to 2016 suggests transmission of the virus between the two countries and a separate and parallel development from European or other Israeli BTV-8 strains. The parallel development of other BTV-8 strains was demonstrated by the identification of the Israeli BTV-8 ISR-1194/1/19 strain, which exhibited common origin with reassorted Israeli BTV-8 strains from 2010 and additional reassortment of seven segments. In order to reveal the source of BTV-8 introduction into Israel we performed BEAST analysis which showed that a probable common ancestor for both European and Israeli BTV-8 presumably existed in 2003-2004. In 2019, a possible new introduction occurred in Israel, where a novel BTV-8 strain was detected, sharing ~95% identity by segments 2 and 6 with Nigerian BTV-8NIG1982/07 and European-Middle Eastern strains. The results of the study indicate that Israel and neighboring countries consist a separate environmental and evolutionary system, distinct from European ones.
欧洲蓝舌病病毒8型（BTV-8）的疫情以数年无活动期分隔的活动周期为特征，可能受到病毒的基因变化或群体免疫的影响。以色列的BTV活动具有相似的动态，但在媒介种群、环境条件以及缺乏针对该血清型的牛疫苗接种方面与欧洲国家不同。因此，比较这两个地理系统并表征它们的流行病学联系对于更好地理解影响BTV-8进化的因素具有很高的研究价值。与欧洲毒株密切相关的BTV-8于2008年传入以色列。它在2010年以及2015 - 2016年的蓝舌病疫情中处于中心位置，此后于2019年在以色列最后一次被分离出来。我们对2008年至2019年间分离的12株以色列BTV-8毒株进行了基因分析，并将它们与其他国家分离的BTV-8已发表序列进行了比较。分析显示BTV-8单次传入以色列，此后基因组漂移广泛发生，并与当地BTV毒株发生多次重配。对2015年至2016年以色列和塞浦路斯的BTV-8进行比较表明，该病毒在两国之间传播，并且与欧洲或其他以色列BTV-8毒株独立并行发展。通过鉴定以色列BTV-8 ISR-1194/1/19毒株证明了其他BTV-8毒株的并行发展，该毒株与2010年重配的以色列BTV-8毒株有共同起源，并发生了七个片段的额外重配。为了揭示BTV-8传入以色列的来源，我们进行了贝叶斯进化分析，结果表明欧洲和以色列BTV-8可能的共同祖先大概存在于2003 - 2004年。2019年，以色列可能发生了一次新的传入事件，检测到一种新型BTV-8毒株，其第2和第6片段与尼日利亚BTV-8NIG1982/07以及欧洲 - 中东毒株具有约95%的同一性。研究结果表明，以色列及其邻国构成了一个与欧洲不同的独立环境和进化系统。
