Paddock C D, Yabsley M J
Division of Viral and Rickettsial Diseases, National Center for Infectious Diseases, Centers for Disease Control and Prevention, Atlanta, GA, USA.
Curr Top Microbiol Immunol. 2007;315:289-324. doi: 10.1007/978-3-540-70962-6_12.
Two infectious diseases, and one presumably infectious disease, each vectored by or associated with the bite of the lone star tick (Amblyomma americanum), were identified and characterized by clinicians and scientists in the United States during the 1980s and 1990s. These three conditions-human monocytic (or monocytotropic) ehrlichiosis (HME), Ehrlichia ewingii ehrlichiosis, and southern tick-associated rash illness (STARI)-undoubtedly existed in the United States prior to this time. However, the near-simultaneous recognition of these diseases is remarkable and suggests the involvement of a unifying process that thrust multiple pathogens into the sphere of human recognition. Previous works by other investigators have emphasized the pivotal role of white-tailed deer (Odocoileus virginianus) in the emergence of Lyme disease, human babesiosis, and human granulocytic anaplasmosis. Because whitetails serve as a keystone host for all stages of lone star ticks, and an important reservoir host for Ehrlichia chaffeensis, E. ewingii, and Borrelia lonestari, the near-exponential growth of white-tailed deer populations that occurred in the eastern United States during the twentieth century is likely to have dramatically affected the frequency and distribution of A. americanum-associated zoonoses. This chapter describes the natural histories of the pathogens definitively or putatively associated with HME, E. ewingii ehrlichiosis, and STARI; the role of white-tailed deer as hosts to lone star ticks and the agents of these diseases; and the cascade of ecologic disturbances to the landscape of the United States that have occurred during the last 200 years that provided critical leverage in the proliferation of white-tailed deer, and ultimately resulted in the emergence of these diseases in human populations.
20世纪80年代和90年代，美国的临床医生和科学家识别并描述了两种传染病以及一种可能的传染病，它们均由孤星蜱（美洲钝缘蜱）叮咬传播或与之相关。这三种病症——人单核细胞埃立克体病（HME）、尤因埃立克体病以及南方蜱传皮疹病（STARI）——无疑在此之前就已在美国存在。然而，这些疾病几乎同时被发现，这一点值得注意，表明存在一个统一的过程，使得多种病原体进入人类认知范围。其他研究人员之前的工作强调了白尾鹿（弗吉尼亚鹿）在莱姆病、人巴贝斯虫病和人粒细胞无形体病出现过程中的关键作用。由于白尾鹿是孤星蜱各阶段的关键宿主，以及查菲埃立克体、尤因埃立克体和伯氏疏螺旋体的重要储存宿主，20世纪美国东部白尾鹿数量近乎指数级增长，很可能极大地影响了与美洲钝缘蜱相关的人畜共患病的发生频率和分布。本章描述了与HME、尤因埃立克体病和STARI明确或推定相关的病原体的自然史；白尾鹿作为孤星蜱和这些疾病病原体宿主的作用；以及过去200年中美国景观发生的一系列生态干扰，这些干扰为白尾鹿的繁殖提供了关键助力，最终导致这些疾病在人类中出现。
