Laboratory of Vector-Borne Infections, FSPSI Scientific Centre for Family Health and Human Reproduction Problems (SC FHHRP), Irkutsk, Russian Federation.
Selengie Aimag Department, National Center For Zoonotic Diseases, Sukhbaatar, Mongolia.
Parasit Vectors. 2022 Jun 28;15(1):236. doi: 10.1186/s13071-022-05356-x.
In Mongolia, the taiga tick Ixodes persulcatus is the major vector of tick-borne pathogens. Knowledge about co-infections of these pathogens in ticks is necessary both for understanding their persistence in nature and for diagnosing and treating tick-borne diseases.
The prevalence of seven tick-borne infections in 346 I. persulcatus collected from the Selenge and Bulgan provinces of Mongolia was evaluated using real-time PCR. Quantification of Borrelia spp. was performed using multiplex quantitative PCR targeting the 16S rRNA gene. Genetic analysis of Borrelia spp. in 11 ticks infected with Borrelia miyamotoi, including six ticks co-infected with Borrelia burgdorferi sensu lato (s.l.), was performed by high-throughput sequencing of the flaB gene fragment.
Six ticks (1.7%) were infected with tick-borne encephalitis virus (TBEV); 171 (49.4%), with B. burgdorferi sensu lato; 17 (4.9%), with B. miyamotoi; 47 (13.6%), with Anaplasma phagocytophilum; and 56 (16.2%), with Ehrlichia sp. Neither Rickettsia sibirica nor R. heilongjiangensis were detected. Borrelia burgdorferi s.l. occurred as co-infection in 55 (32.2%) of all infected ticks. The other pathogens co-infected ticks in 58.8-70.2% of cases. No pairwise associations between co-infecting pathogens were observed, with the exception of a positive association between A. phagocytophilum and Ehrlichia sp.
The spirochete loads of B. miyamotoi were significantly higher than those of B. burgdorferi s.l. (mean: 5.2 vs 4.0 log10 genome copies/tick, respectively). Ten isolates of B. miyamotoi belonged to the Siberian lineage. Borrelia burgdorferi s.l was represented by nine isolates of B. afzelii, B. bavariensis and B. garinii.
In populations of I. persulcatus inhabiting the Selenge and Bulgan provinces of Mongolia, five vector-borne pathogens, i.e. TBEV, B. burgdorferi s.l., B. miyamotoi, A. phagocytophilum and Ehrlichia sp., persist independently from each other, with the exception of A. phagocytophilum and Ehrlichia sp. which seem to share the circulation mode. The discrepancies in B. burgdorferi s.l. and B. miyamotoi prevalence and spirochete load per tick suggest that different ecological niches are occupied by Lyme disease and relapsing fever agents. High-throughput sequencing allows genetic identification of borreliae species in co-infected ticks.
在蒙古，长角血蜱Ixodes persulcatus 是蜱传病原体的主要媒介。了解这些病原体在蜱中的共同感染情况，对于理解它们在自然界中的持续存在以及诊断和治疗蜱传疾病都是必要的。
使用实时 PCR 评估从蒙古 Selenge 和 Bulgan 省采集的 346 只长角血蜱中七种蜱传感染的流行情况。使用针对 16S rRNA 基因的多重定量 PCR 对 Borrelia spp. 进行定量。对 11 只感染 Borrelia miyamotoi 的蜱进行 Borrelia spp. 的基因分析，包括 6 只感染 Borrelia burgdorferi sensu lato (s.l.) 的蜱，通过 flaB 基因片段的高通量测序进行。
6 只蜱（1.7%）感染了蜱传脑炎病毒（TBEV）；171 只（49.4%）感染了 Borrelia burgdorferi sensu lato；17 只（4.9%）感染了 Borrelia miyamotoi；47 只（13.6%）感染了嗜吞噬细胞无形体；56 只（16.2%）感染了埃立克体。未检测到西伯利亚立克次体或黑龙江立克次体。Borrelia burgdorferi s.l. 是所有感染蜱中的 55 只（32.2%）的共感染。其他病原体在 58.8-70.2%的情况下共感染蜱。除了嗜吞噬细胞无形体和埃立克体之间存在正相关外，未观察到共感染病原体之间存在任何关联。
Borrelia miyamotoi 的螺旋体负荷明显高于 Borrelia burgdorferi s.l.（平均：5.2 与 4.0 log10 基因组拷贝/蜱，分别）。10 株 Borrelia miyamotoi 属于西伯利亚谱系。Borrelia burgdorferi s.l. 由 9 株分离株组成，分别为 B. afzelii、B. bavariensis 和 B. garinii。
在蒙古 Selenge 和 Bulgan 省的长角血蜱种群中，五种虫媒病原体，即 TBEV、Borrelia burgdorferi s.l.、Borrelia miyamotoi、嗜吞噬细胞无形体和埃立克体，彼此独立存在，除了嗜吞噬细胞无形体和埃立克体似乎共享循环模式外。Borrelia burgdorferi s.l. 和 Borrelia miyamotoi 的流行率和每只蜱的螺旋体负荷的差异表明，莱姆病和回归热病原体占据不同的生态位。高通量测序允许对共感染蜱中的伯氏疏螺旋体进行基因鉴定。
