Watt George, Parola Philippe
Department of Retrovirology, Armed Forces Research Institute of Medical Sciences, Bangkok, Thailand.
Curr Opin Infect Dis. 2003 Oct;16(5):429-36. doi: 10.1097/00001432-200310000-00009.
Recent developments in molecular taxonomic methods have led to a reclassification of rickettsial diseases. The agent responsible for scrub typhus (Orientia tsutsugamushi ) has been removed from the genus Rickettsia and a bewildering array of new rickettsial pathogens have been described. An update of recent research findings is therefore particularly timely for the nonspecialist physician.
An estimated one billion people are at risk for scrub typhus and an estimated one million cases occur annually. The disease appears to be re-emerging in Japan, with seasonal transmission. O. tsutsugamushi has evolved a variety of mechanisms to remain viable in its intracellular habitat. Slowing the release of intracellular calcium inhibits apoptosis of macrophages. Subsets of chemokine genes are induced in infected cells, some in response to transcription factor activator protein 1. Cardiac involvement is uncommon and clinical complications are predominantly pulmonary. Serious pneumonitis occurred in 22% of Chinese patients. Dual infections with leptospirosis have been reported. Standardized diagnostic tests are being developed and attempts to improve treatment of women and children are being made. Of the numerous tick-borne rickettsioses identified in recent years, African tick-bite fever appears to be of particular importance to travellers. The newly described flea-borne spotted fever caused by Rickettsia felis may be global in distribution.
Rash and fever in a returning traveler could be rickettsial and presumptive doxycycline treatment can be curative. Recent research findings raise more questions than answers and should stimulate much needed research.
分子分类学方法的最新进展导致了立克次体病的重新分类。恙虫病东方体（Orientia tsutsugamushi）已从立克次体属中移除，并且描述了一系列令人困惑的新立克次体病原体。因此，对于非专科医生来说，及时更新近期的研究发现尤为重要。
估计有10亿人有感染恙虫病的风险，每年估计有100万病例发生。该疾病在日本似乎正在重新出现，呈季节性传播。恙虫病东方体已经进化出多种机制以在其细胞内栖息地中存活。减缓细胞内钙的释放可抑制巨噬细胞的凋亡。感染细胞中可诱导趋化因子基因的亚群，其中一些是对转录因子激活蛋白1的反应。心脏受累并不常见，临床并发症主要是肺部的。22%的中国患者发生了严重肺炎。已报告有钩端螺旋体双重感染的情况。正在开发标准化诊断测试，并尝试改善对妇女和儿童的治疗。在近年来发现的众多蜱传立克次体病中，非洲蜱咬热似乎对旅行者尤为重要。新描述的由猫立克次体引起的蚤传斑点热可能在全球范围内分布。
回国旅行者出现皮疹和发热可能是立克次体病，经验性使用强力霉素治疗可能治愈。近期的研究发现提出的问题多于答案，应该激发急需的研究。
