INTERSPECIFIC COMPETITION BETWEEN RICKETTSIAE IN TICKS

在自然界中，单个蜱虫可以同时感染更多的 比一种细胞内的细菌要多。 有些可能是重要的人类 病原体从感染性血液中获得， 经卵巢 其他可能是非致病性共生体获得 经卵巢 的后果和流行病学意义 蜱虫中的多种细菌感染在很大程度上是未探索的。 我们 我认为某些细胞内 单个蜱虫内的细菌种类可能足以 改变蜱虫媒介能力的流行率和幅度。 安氏革蜱的卵巢含有一种特殊的 非致病性斑点热群立克次体，即 孔雀立克次体，已被证明是难治性的后续合作， 感染其他侵入性R.立克次氏体 因此，卵巢 感染D. andersoni和R.孔雀立克次体干扰素 阻断R.立克次氏体 感染 两种或两种以上密切相关的立克次体的感染可能导致 在干扰中（即，一个物种抑制发育和/或 另一个的传递），互利共生（即，增强传输 两个物种），或表型混合（即，增加或减少 毒力）。 该提案专门针对经卵巢 人类病原体立克次体对蜱的干扰 经卵感染非致病性立克次体的载体。 我们将 研究跨卵巢干扰的现象 它的流行病学意义及其机制， 发生。 提出了两个具体目标：1）我们将调查 R. 其他本土非致病性物种作为药物的立克次氏体 斑点热群立克次体D. andersoni和D.变量 这将需要实地收集蜱虫和进行实验室评价 这些物质的干扰潜力;以及2）我们将启动 研究检查经卵巢的分子机制 干扰R.立克次氏体R.孔雀和其他非致病性 斑点热群立克次体。

In nature, individual ticks can be concomittently infected with more than one species of intracellular bacteria. Some may be important human pathogens acquired either from an infectious bloodmeal or transovarially. Others may be nonpathogenic symbionts acquired transovarially. The consequences and epidemiological significance of multiple bacterial infections in ticks are largely unexplored. We propose that the interactive effects between certain intracellular bacterial species within individual ticks may be of sufficient prevalence and magnitude to alter the vector competence of ticks. Ovaries of Dermacentor andersoni ticks harboring a particular nonpathogenic species of spotted fever group rickettsia, namely Rickettsia peacockii, have been shown to be refractory to subsequent co- infection with otherwise invasive R. rickettsii. Thus, ovarial infection of D. andersoni with R. peacockii rickettsiae interferes or blocks normal transovarial transmission of R. rickettsii. Infections with two or more closely-related rickettsial species may result either in interference (i.e., one species inhibits the development and/or transmission of the other), mutualism (i.e., enhanced transmission of both species), or phenotypic mixing (i.e., increased or decreased virulence). This proposal specifically addresses transovarial interference of the human pathogen, Rickettsia rickettsii, in the tick vector transovarially infected with nonpathogenic rickettsiae. We will investigate the phenomenon of transovarial interference in the context of its epidemiological significance and the mechanism(s) by which it occurs. Two specific aims are proposed: 1) We will investigate the prevalence and relative efficiency of transovarial interference of R. rickettsii as medicated by other indigenous species of nonpathogenic spotted fever group rickettsiae within D. andersoni and D. variabilis. This will entail field collections of ticks and laboratory evaluation of the interference potential of these agents; and 2) We will initiate studies to examine the molecular mechanism (s) of transovarial interference of R. rickettsii by R. peacockii and other nonpathogenic spotted fever group rickettsiae.