莱姆病细菌在其蜱虫载体中的性别二态性——伯氏疏螺旋体在雌性肩突硬蜱幼虫中的丰度高于雄性。

Sexual dimorphism of the Lyme disease bacterium in its tick vector - Abundance of Borrelia burgdorferi is higher in female than male Ixodes scapularis larvae.

作者信息

Koloski Cody W, Adam Hesham, Siddiqa Azka, Bourgeois Brooklyn, Chilton Neil B, Gulia-Nuss Monika, Voordouw Maarten J

机构信息

Department of Veterinary Microbiology, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Canada.

Department of Biology, College of Arts and Sciences, University of Saskatchewan, Saskatoon, Canada.

出版信息

Ticks Tick Borne Dis. 2025 Aug 19;16(5):102539. doi: 10.1016/j.ttbdis.2025.102539.

DOI:10.1016/j.ttbdis.2025.102539

PMID:40834820

Abstract

BACKGROUND

In North America, the tick-borne spirochete Borrelia burgdorferi sensu stricto (ss) causes Lyme disease and is transmitted by the blacklegged tick, Ixodes scapularis. Acquisition and transmission of B. burgdorferi ss occur during blood feeding, which is done by three tick stages, larvae, nymphs, and adults. Sex-specific differences in tick body size and blood feeding behaviour may influence transmission of tick-borne pathogens. However, sex-specific molecular markers are needed for sex determination of immature ticks. The objective of this study was to determine whether tick sex influences the acquisition and abundance of B. burgdorferi ss in immature I. scapularis ticks.

METHODS

Uninfected or B. burgdorferi-infected larvae and nymphs were fed on B. burgdorferi-infected or uninfected lab mice and allowed to moult into the next stage. The sex of immature and adult ticks was determined using sex-specific PCR. The presence and abundance of B. burgdorferi in ticks were determined using 23S rRNA qPCR, and the amount of tick tissue was determined using tick calreticulin qPCR.

RESULTS

There was no difference in acquisition of B. burgdorferi between immature male and female I. scapularis. In engorged larvae, the spirochete load was 45.7 % higher in female larvae compared to male larvae, and this difference was significant. In 4-week-old unfed nymphs, the spirochete load was 7.4 % higher in female nymphs compared to male nymphs, but this difference was not significant. In engorged larvae, the tick calreticulin gene content was similar between the sexes, whereas in unfed nymphs, the calreticulin gene content was 12.6 % higher in females than males, suggesting that female nymphs are larger. In adult ticks, female ticks weighed more, had higher calreticulin gene content, and higher spirochete loads than adult male ticks. Future studies should investigate whether tick sex influences the vector competence of Ixodes ticks for other tick-borne pathogens.

摘要

背景

在北美，蜱传播的螺旋体伯氏疏螺旋体狭义种（Borrelia burgdorferi sensu stricto，ss）可引发莱姆病，由黑腿蜱肩突硬蜱（Ixodes scapularis）传播。伯氏疏螺旋体狭义种的获取与传播发生在蜱吸血过程中，蜱的幼虫、若虫和成虫三个阶段都会吸血。蜱虫体型和吸血行为的性别差异可能会影响蜱传播病原体的传播。然而，需要性别特异性分子标记来确定未成熟蜱的性别。本研究的目的是确定蜱的性别是否会影响未成熟肩突硬蜱中伯氏疏螺旋体狭义种的获取和数量。

方法

将未感染或感染伯氏疏螺旋体的幼虫和若虫置于感染或未感染伯氏疏螺旋体的实验室小鼠身上吸血，然后让其蜕皮进入下一阶段。使用性别特异性PCR确定未成熟蜱和成年蜱的性别。通过23S rRNA定量PCR确定蜱中伯氏疏螺旋体的存在和数量，并通过蜱钙网蛋白定量PCR确定蜱组织的量。

结果

未成熟的雄性和雌性肩突硬蜱在获取伯氏疏螺旋体方面没有差异。在饱血幼虫中，雌性幼虫的螺旋体载量比雄性幼虫高45.7%，且这种差异具有统计学意义。在4周龄未吸血的若虫中，雌性若虫的螺旋体载量比雄性若虫高7.4%，但这种差异不具有统计学意义。在饱血幼虫中，两性的蜱钙网蛋白基因含量相似，而在未吸血若虫中，雌性的钙网蛋白基因含量比雄性高12.6%，这表明雌性若虫体型更大。在成年蜱中，雌性蜱比成年雄性蜱体重更重，钙网蛋白基因含量更高，螺旋体载量也更高。未来的研究应调查蜱的性别是否会影响肩突硬蜱对其他蜱传播病原体的媒介能力。