背景:微孢子虫是一大类真核专性细胞内孢子形成寄生虫,其中17种可引起人类微孢子虫病。大多数人类感染的微孢子虫属于肠孢子虫属和头孢菌素属。迄今为止,只有五种微孢子虫,包括类似于头孢菌素的,使用显微镜方法在硬蜱(Ixodidae)中发现,但是没有序列数据。此外,迄今为止,尚未对基于DNA分析的微孢子虫感染蜱进行广泛筛查.因此,在这项研究中,我们应用了一种最近开发的DNA元编码方法来进行有效的微孢子虫DNA鉴定,以评估壁虱作为引起人类疾病的微孢子虫物种的潜在载体的作用。
方法:总共,在波兹南市的城市公园收集了1070(493名少年和577名成年人)未进食的寻求寄主的蓖麻蜱虫,波兰,并对94只以狗和猫为食的吞食蜱雌性进行了微孢子虫DNA筛查。使用微孢子虫特异性引物组,通过PCR扩增和18SrRNA基因的高变V5区测序(18S谱分析)来检测微孢子虫。在形态上鉴定了蜱虫种类,并通过扩增和测序细胞色素c氧化酶亚基I基因(mini-COI)的缩短片段来确认。
结果:所有收集的蜱被明确地分配给蓖麻。在从三只不同的狗中收集的三只饲喂的蜱虫(3.2%)中鉴定出潜在的人畜共患的头孢菌素肠。在八个未喂食的寻找宿主的蜱中(0.8%),包括三名男性(1.1%),两名女性(0.7%)及三名若虫(0.7%),鉴定了新的微孢子虫序列,该序列代表了一种属于内网属的物种。
结论:在寻找宿主的蜱中缺乏人畜共患的小孢子虫,这表明蓖麻与感染人类的小孢子虫的传播无关。此外,在进食和寻求寄主的蜱中,其他微孢子虫的发生率非常低,这表明存在保护蜱免受这些寄生虫感染的机制。
BACKGROUND: Microsporidia is a large group of eukaryotic obligate intracellular spore-forming parasites, of which 17 species can cause microsporidiosis in humans. Most human-infecting microsporidians belong to the genera Enterocytozoon and Encephalitozoon. To date, only five microsporidian species, including Encephalitozoon-like, have been found in hard ticks (Ixodidae) using microscopic methods, but no sequence data are available for them. Furthermore, no widespread screening for microsporidian-infected ticks based on DNA analysis has been carried out to date. Thus, in this study, we applied a recently developed DNA metabarcoding method for efficient microsporidian DNA identification to assess the role of ticks as potential vectors of microsporidian species causing diseases in humans.
METHODS: In total, 1070 (493 juvenile and 577 adult) unfed host-seeking Ixodes ricinus ticks collected at urban parks in the city of Poznan, Poland, and 94 engorged tick females fed on dogs and cats were screened for microsporidian DNA. Microsporidians were detected by PCR amplification and sequencing of the hypervariable V5 region of 18S rRNA gene (18S profiling) using the microsporidian-specific primer set. Tick species were identified morphologically and confirmed by amplification and sequencing of the shortened fragment of cytochrome c oxidase subunit I gene (mini-COI).
RESULTS: All collected ticks were unambiguously assigned to I. ricinus. Potentially zoonotic Encephalitozoon intestinalis was identified in three fed ticks (3.2%) collected from three different dogs. In eight unfed host-seeking ticks (0.8%), including three males (1.1%), two females (0.7%) and three nymphs (0.7%), the new microsporidian sequence representing a species belonging to the genus Endoreticulatus was identified.
CONCLUSIONS: The lack of zoonotic microsporidians in host-seeking ticks suggests that I. ricinus is not involved in transmission of human-infecting microsporidians. Moreover, a very low occurrence of the other microsporidian species in both fed and host-seeking ticks implies that mechanisms exist to defend ticks against infection with these parasites.