Laboratory of Wildlife Biology and Medicine, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, Japan.
Vector Borne Zoonotic Dis. 2013 Feb;13(2):92-7. doi: 10.1089/vbz.2012.1027. Epub 2012 Dec 4.
To clarify how Borrelia miyamotoi is maintained in the environment in Hokkaido, we examined Ixodes persulcatus for its prevalence among wild rodents and its tick vector by detecting a portion of the borrelial flaB gene in rodent urinary bladder and blood samples, and from whole ticks. We compared B. miyamotoi infection rates to Borrelia garinii and Borrelia afzelii, which are human Lyme disease pathogens also carried by wild rodents, and which are transmitted by the same vector tick. Whereas B. garinii and B. afzelii showed age dependence of infection rates among wild rodents (18.4% and 9.9% among adults and 6.0% and 3.4% among sub-adults, respectively) when looking at urinary bladder samples, B. miyamotoi infection rates were not age dependent for either blood (4.2% among adults, and 7.9% among sub-adults) or urinary bladder samples (1.0% among adults, and 1.7% among sub-adults). Moreover, while B. garinii and B. afzelii infection rates showed increases across months (June, July [p<0.05] and August [p<0.01] had higher rates than in May for adult rodents with B. garinii, and July and August had higher rates than in May [p<0.01] for adult rodents with B. afzelii), B. miyamotoi infection rates did not show significant month dependence. These differences in month and age dependence led us to suspect that B. miyamotoi may not develop persistent infections in wild rodents, as B. garinii and B. afzelii are thought to. Furthermore, we examined the extent of rodent exposure to I. persulcatus nymphs and larvae throughout most of the tick's active season (May through September), and determined that B. miyamotoi infection rates in sub-adult rodents were correlated with larval burden (p<0.01), suggesting that larvae may be very important in transmission of B. miyamotoi to wild rodents.
为了阐明伯氏疏螺旋体在北海道的环境中是如何维持的，我们通过检测啮齿动物膀胱和血液样本以及整蜱中的一部分螺旋体 flaB 基因，检查了野生啮齿动物中伊氏革蜱的流行情况及其作为蜱传媒介。我们将伯氏疏螺旋体的感染率与伯氏包柔螺旋体和阿菲莱姆包柔螺旋体进行了比较，这两种螺旋体也是人类莱姆病的病原体，也存在于野生啮齿动物中，并且由相同的媒介蜱传播。虽然在观察膀胱样本时，伯氏包柔螺旋体和阿菲莱姆包柔螺旋体的感染率在野生啮齿动物中存在年龄依赖性（成年组为 18.4%和 9.9%，亚成年组为 6.0%和 3.4%），但在血液（成年组为 4.2%，亚成年组为 7.9%）或膀胱样本（成年组为 1.0%，亚成年组为 1.7%）中，伯氏疏螺旋体的感染率不受年龄影响。此外，虽然伯氏包柔螺旋体和阿菲莱姆包柔螺旋体的感染率随着月份的增加而增加（6 月、7 月[p<0.05]和 8 月[p<0.01]比 5 月的成年啮齿动物的感染率更高），但 7 月和 8 月比 5 月[5 月的感染率更高]（p<0.01]）阿菲莱姆包柔螺旋体感染率随着月份的增加而增加，但伯氏疏螺旋体的感染率没有明显的月份依赖性。这种月份和年龄依赖性的差异使我们怀疑伯氏疏螺旋体可能不会像伯氏包柔螺旋体和阿菲莱姆包柔螺旋体那样在野生啮齿动物中形成持续感染。此外，我们在整个蜱活跃季节（5 月至 9 月）内检查了啮齿动物暴露于伊氏革蜱幼蜱和若蜱的程度，并确定亚成年啮齿动物的伯氏疏螺旋体感染率与幼蜱负担相关（p<0.01），这表明幼蜱在伯氏疏螺旋体向野生啮齿动物的传播中可能非常重要。
