Hodzic E, Fish D, Maretzki C M, De Silva A M, Feng S, Barthold S W
Center for Comparative Medicine, Schools of Medicine and Veterinary Medicine, University of California, Davis, California 95616, USA.
J Clin Microbiol. 1998 Dec;36(12):3574-8. doi: 10.1128/JCM.36.12.3574-3578.1998.
The purpose of the present study was to investigate the transmission of a human isolate of the agent of human granulocytic ehrlichiosis (HGE agent) from infected mice to larval ticks and to examine the population kinetics of the HGE agent in different stages of the tick life cycle. The HGE agent was quantitated by competitive PCR with blood from infected mice and with Ixodes scapularis ticks. The median infectious dose for C3H mice was 10(4) to 10(5) organisms when blood from an infected severe combined immunodeficient mouse was used as an inoculum. Uninfected larval ticks began to acquire infection from infected mice within 24 h of attachment, and the number of HGE agent organisms increased in larval ticks during feeding and after detachment of replete ticks. Molted nymphal ticks, infected as larvae, transmitted infection to mice between 40 and 48 h of attachment. Onset of feeding stimulated replication of the HGE agent within nymphal ticks. These studies suggest that replication of the HGE agent during and after feeding in larvae and during feeding in nymphs is a means by which the HGE agent overcomes inefficiencies in acquisition of infection by ticks and in tick-borne transmission to mammalian hosts.
本研究的目的是调查人粒细胞无形体病病原体（HGE病原体）的一株人分离株从感染小鼠向幼蜱的传播情况，并研究HGE病原体在蜱虫不同生命周期阶段的种群动力学。通过竞争性PCR对感染小鼠的血液和肩突硬蜱中的HGE病原体进行定量。当使用来自感染严重联合免疫缺陷小鼠的血液作为接种物时，C3H小鼠的半数感染剂量为10⁴至10⁵个病原体。未感染的幼蜱在附着后24小时内开始从感染小鼠获得感染，饱血蜱脱落前后，幼蜱体内HGE病原体数量增加。作为幼虫时被感染的若蜱，在附着后40至48小时内将感染传播给小鼠。开始取食刺激若蜱体内HGE病原体的复制。这些研究表明，HGE病原体在幼虫取食期间及之后以及若虫取食期间的复制，是HGE病原体克服蜱虫获取感染以及蜱传向哺乳动物宿主效率低下的一种方式。
