ECOLOGY OF CHIGGER-BORNE RICKETTSIOSIS (SCRUB TYPHUS)1,2
ECOLOGY OF CHIGGER-BORNE RICKETTSIOSIS (SCRUB TYPHUS)1,2
复制标题
DOI：
10.1093/jmedent/11.3.237
复制
发表时间：
1974-01-01
影响因子：
2.1
通讯作者：
WISSEMAN, CL
中科院分区：
文献类型：
--
作者：
TRAUB, R;WISSEMAN, CL
恙螨传播的立克次体病（恙虫病）的生态学的批判性审查，提出了一个综合的基础上发表和未发表的信息。恙螨传播斑疹伤寒的所有流行病学特征都可归因于媒介恙螨的习性和其他特征。这种立克次体病在非常广泛的栖息地中被发现，可能存在于从半荒漠到高山地带的山区，从桑迪到茂密但受干扰的森林的所有地区，这些地区有恙螨群和鼠属野鼠共存。这些生境的特点是存在着人为或自然造成的不断变化的生态条件，并表现为过渡类型的植被，即使这些植被是在沿着丛林溪流的有限集中地。鼠、恙螨和次生植被（它们与病原体恙虫病立克次体一起构成“人畜共患四分体”）之间的密切联系是一种古老的联系。我们假设，作为Rattus和相关的恙螨亚属Leptotrombidium渗透到新的地区和栖息地，他们多样化，并作为恙螨适应其他主机在新的地区，这些哺乳动物成为次要参与立克次体病的生态。在L。deliense-group构成了这种疾病的主要媒介，我们认为它们也是自然界中感染的主要宿主，通过自然感染的雌性螨将立克次体经卵巢传播到下一代，使循环持续下去。虽然恙螨可以通过进食从啮齿类宿主获得立克次体，但实验室数据表明，这很少会导致另一种哺乳动物感染，无论是通过在进食时感染的恙螨，然后重新附着到第二个宿主（这本身是不寻常的），还是通过经卵感染的后代。然而，虽然这样的事件可能很难在实验室中证明，但在野外同样低的成功率在自然周期中将是重要的，因为涉及大量的恙螨，并且因为在几代人的时间内，获得性感染的经卵巢传播会随之放大。小型哺乳动物（“兽”），如大鼠、田鼠和树鼩，主要居住在地面上，在立克次体病的生态学中是重要的，因为它们是媒介恙螨的主要宿主。树栖啮齿类动物和啮齿类动物在感染中起的作用很小，显然是因为它们很少接触到L.恙虫立克次体与该属的其他成员显著不同，它们之间的相似性显然代表了在哺乳动物和节肢动物中作为具有周期的细胞内寄生虫存在的趋同。与此相反，所谓的病原体血清型却大相径庭。某些血清型的广泛分布，以及它们可以由几种恙螨传播的事实表明，从治疗中获得的感染在立克次体病的生态学中可能是重要的。利用L. deliense复合体和野鼠作为存在这种感染的指标，“绿洲恙螨传播立克次体病”已在“生态岛屿”的残遗动物群中得到证实。这些动物数据表明，感染可能存在于尚未证实的地区，如伊朗北方和苏联南部的一些共和国，西藏、新疆等地的部分地区。
A critical review of the ecology of chigger-borne rickettsiosis (scrub typhus) is presented, based upon a synthesis of both published and unpublished information. All the epidemiological characteristics of chigger-borne typhus are attributable to the habits and other features of the vector chiggers. This rickettsiosis is found in a remarkably broad range of habitats, presumably in all areas where members of theLeptotrombidium deliense-group of chiggers and wild rats of the genusRattuscoexist, ranging from semideserts to alpine reaches in the mountains, and from sandy beaches to dense but disturbed forest. The habitats are characterized by the presence of changing ecological conditions, wrought by man or nature, and expressed by transitional types of vegetation, even if these are in circumscribed foci as along jungle streams. The intimate association between the rats, chiggers and secondary vegetation (which together withRickettsia tsutsugamushi, the etiological agent, constitute the “zoonotic tetrad”) is an ancient one. We postulate that asRattusand associated chiggers of the subgenusLeptotrombidiumpenetrated new areas and habitats, they diversified, and as the chiggers adapted to other hosts in the new regions, such mammals became secondarily involved in the ecology of the rickettsiosis. Chiggers in theL. deliense-group constitute the major vectors of this disease, and we consider that they also serve as the primary reservoir of the infection in nature, perpetuating the cycle by transovarian transmission of the rickettsiae from the naturally infected female mite to the next generation. While chiggers can acquire rickettsiae from a rodent host by feeding, laboratory data suggest that only rarely can this result in infection in another mammal, whether by a chigger that has become infected while feeding and then reattaching to a second host (which is unusual in itself) or by transovarially infected progeny. However, while such an event may be difficult to demonstrate in the laboratory, the same low percentage of success in the field would be significant in the natural cycle because of the vast numbers of chiggers involved, and because of the amplification that would ensue by transovarian transmissionof acquired infection over a period of generations. Small mammals (“theraphions”) like rats, voles, and tree-shrews which are primarily ground-dwelling are important in the ecologyof the rickettsiosis by serving as major hosts of the vector chiggers. Arboreal rodents and commensal rats play little role in the infection, apparently because they seldom come in contact with ground infested with theL. deliense-group.Rickettsia tsutsugamushidiffers significantly from other members of the genus, and the similarities between them apparently represent convergence towards existence as intracellular parasites with cycles in both mammals and arthropods. The so-called serotypes of the agent, in contrast, are quite divergent. The widespread range of certain serotypes, and the fact that they may be transmitted by several species of chiggers suggest that infection acquired from theraphions may be significant in the ecology of the rickettsiosis. By using chiggers of theL. deliense-complex and wild rats as indicators of the presence of this infection, “oasis chigger-borne rickettsiosis” has been demonstrated among relict faunae in “ecological islands.” Such faunal data indicate that the infection may be present in areas where it has not yet been demonstrated, as in northern Iran and some southern republics of the U.S.S.R., parts of Tibet, Sinkiang, etc.