Crimean-Congo Hemorrhagic Fever Virus Clades V and VI (Europe 1 and 2) in Ticks in Kosovo, 2012

Despite being a small country, Kosovo represents one of the few foci of Crimean-Congo hemorrhagic fever (CCHF) in Europe. The distribution of Kosovar tick vectors and the evolution of CCHF virus in ticks are both as yet unknown. A better description of the extent and the genetic diversity of CCHFV in ticks from endemic settings is essential, in order to be controlled. We investigated the 2012 distribution of Kosovar ticks alongside the prevalence and the phylogeography of tick-derived CCHFV. Hyalomma marginatum dominated in the endemic municipalities with 90.2% versus 24.3% in the non-endemic regions. Of 1,102 tested ticks, 40 (3.6%) were CCHFV-positive, belonging to H. marginatum (29), Rhipicephalus bursa (10), and Ixodes ricinus (1). The virus strains clustered with clade V and VI related sequences. They fell into two lineages: Kosovo I and II. Kosovo I comprised strains recovered exclusively from R. bursa ticks and was closely related to AP92 prototype strain. Kosovo II clustered into Kosovo IIa, including human-derived strains, and IIb including only strains detected in H. marginatum and I. ricinus. Our phylogeographic reconstruction suggests two temporally distinct CCHFV introductions: the most probable location of the most recent common ancestor of Kosovo I lineage was in Greece (63 years ago) and that of lineages IIa-b in Turkey (35 years ago). After each CCHFV introduction into Kosovo, subsequent lineage expansions suggest periods of in situ evolution. The study provides the first insight into the genetic variability and the origin of CCHFV in ticks from Kosovo. Our findings indicate the spreading of CCHFV to non-endemic areas, which underlines the importance of further studies in order to monitor and predict future CCHF outbreaks in Kosovo. The AP92-like strains appear to be more widespread than previously thought and may provide a promising target for experimental studies due to their assumed low pathogenicity.

尽管科索沃领土面积狭小，却是欧洲少数克里米亚-刚果出血热（Crimean-Congo hemorrhagic fever, CCHF）疫区之一。目前，科索沃地区媒介蜱类的分布特征，以及蜱体内克里米亚-刚果出血热病毒（CCHFV）的演化规律均尚不明确。为实现有效防控，明确该病毒在疫区蜱体内的流行范围与遗传多样性至关重要。本研究针对2012年科索沃地区蜱类分布情况，以及蜱源CCHFV的流行率与系统地理学特征展开了调查。边缘璃眼蜱（Hyalomma marginatum）为疫区优势蜱种，占比达90.2%，而非疫区中其占比仅为24.3%。本次检测的1102只蜱样本中，共有40只（3.6%）CCHFV检测呈阳性，其中29只为边缘璃眼蜱，10只为囊形扇头蜱（Rhipicephalus bursa），1只为蓖子硬蜱（Ixodes ricinus）。该病毒毒株与进化枝V、VI的相关序列聚为一支，可划分为两个进化支：科索沃I型与科索沃II型。科索沃I型毒株仅分离自囊形扇头蜱，与AP92原型毒株亲缘关系密切。科索沃II型可进一步分为两个亚型：IIa亚型包含人源毒株，IIb亚型仅包含从边缘璃眼蜱与蓖子硬蜱中检出的毒株。系统地理学重建结果显示，CCHFV存在两次时间上独立的传入事件：科索沃I型进化支的最近共同祖先最可能起源于希腊（距今63年），而IIa-b进化支的最近共同祖先起源于土耳其（距今35年）。每次CCHFV传入科索沃后，后续的进化支扩张均提示病毒在当地发生了原位演化。本研究首次揭示了科索沃地区蜱源CCHFV的遗传变异特征与起源。研究结果表明CCHFV已扩散至非疫区，这凸显了开展后续监测与预测科索沃未来CCHF暴发相关研究的必要性。AP92样毒株的分布范围较此前认知更为广泛，由于其假定的低致病性，有望成为实验研究的理想靶点。