Department of Veterinary Microbiology, Western College of Veterinary Medicine, University of Saskatchewan, 52 Campus Drive, Saskatoon, SK, S7N 5B4, Canada.
Department of Entomology, Faculty of Agricultural and Food Sciences, University of Manitoba, 12 Dafoe Road, Winnipeg, MB, R3T 2N2, Canada.
Parasit Vectors. 2022 Oct 13;15(1):366. doi: 10.1186/s13071-022-05446-w.
Bartonella are intracellular bacteria that are transmitted via animal scratches, bites and hematophagous arthropods. Rodents and their associated fleas play a key role in the maintenance of Bartonella worldwide, with > 22 species identified in rodent hosts. No studies have addressed the occurrence and diversity of Bartonella species and vectors for small mammals in Arctic and Subarctic ecosystems, which are increasingly impacted by invasive species and climate change.
In this study, we characterized the diversity of rodent fleas using conventional PCR targeting the mitochondrial cytochrome c oxidase II gene (COII) and Bartonella species in rodents and shrews (n = 505) from northern Canada using conventional PCR targeting the ITS (intergenic transcribed spacer) region and gltA (citrate synthase) gene. Metagenomic sequencing of a portion of the gltA gene was completed on a subset of 42 rodents and four rodent flea pools.
Year, total summer precipitation the year prior to sampling, average minimum spring temperature and small mammal species were significant factors in predicting Bartonella positivity. Occurrence based on the ITS region was more than double that of the gltA gene and was 34% (n = 349) in northern red-backed voles, 35% (n = 20) in meadow voles, 37% (n = 68) in deer mice and 31% (n = 59) in shrews. Six species of Bartonella were identified with the ITS region, including B. grahamii, B. elizabethae, B. washoensis, Candidatus B. rudakovii, B. doshiae, B. vinsonii subsp. berkhoffii and subsp. arupensis. In addition, 47% (n = 49/105) of ITS amplicons had < 97% identity to sequences in GenBank, possibly due to a limited reference library or previously unreported species. An additional Bartonella species (B. heixiaziensis) was detected during metagenomic sequencing of the gltA gene in 6/11 rodents that had ITS sequences with < 97% identity in GenBank, highlighting that a limited reference library for the ITS marker likely accounted for low sequence similarity in our specimens. In addition, one flea pool from a northern red-backed vole contained multiple species (B. grahamii and B. heixiaziensis).
Our study calls attention to the usefulness of a combined approach to determine the occurrence and diversity of Bartonella communities in hosts and vectors.
巴尔通体是一种通过动物抓挠、咬伤和吸血节肢动物传播的细胞内细菌。啮齿动物及其相关跳蚤在全球范围内维持巴尔通体方面发挥着关键作用，在啮齿动物宿主中已鉴定出超过 22 种。尚无研究探讨北极和亚北极生态系统中小哺乳动物的巴尔通体物种和媒介的发生和多样性，这些生态系统正日益受到入侵物种和气候变化的影响。
在这项研究中，我们使用针对线粒体细胞色素 c 氧化酶 II 基因（COII）的常规 PCR 来描述啮齿动物跳蚤的多样性，并使用针对 ITS（基因间转录间隔区）区域和 gltA（柠檬酸合酶）基因的常规 PCR 来描述来自加拿大北部的啮齿动物和鼩鼱（n=505）中的巴尔通体物种。对一小部分 42 只啮齿动物和四个啮齿动物跳蚤池的 gltA 基因的部分进行了 metagenomic 测序。
采样前一年的总夏季降水量、平均春季最低温度和小哺乳动物物种是预测巴尔通体阳性的重要因素。基于 ITS 区域的出现率是 gltA 基因的两倍多，在北部红背田鼠中为 34%（n=349），在草地田鼠中为 35%（n=20），在鹿鼠中为 37%（n=68），在鼩鼱中为 31%（n=59）。使用 ITS 区域鉴定出六种巴尔通体，包括 B. grahamii、B. elizabethae、B. washoensis、Candidatus B. rudakovii、B. doshiae、B. vinsonii subsp. berkhoffii 和 subsp. arupensis。此外，47%（n=49/105）的 ITS 扩增子与 GenBank 中的序列具有<97%的同一性，这可能是由于参考文库有限或以前未报道的物种。在 gltA 基因的 metagenomic 测序中，6/11 只 ITS 序列在 GenBank 中具有<97%同一性的啮齿动物中检测到另一种巴尔通体（B. heixiaziensis），这突出表明 ITS 标记的参考文库有限可能导致我们标本的序列相似性较低。此外，一只来自北部红背田鼠的跳蚤池包含多个物种（B. grahamii 和 B. heixiaziensis）。
我们的研究提醒人们注意结合使用多种方法来确定宿主和媒介中巴尔通体群落的发生和多样性。
