Proximal determinants of risk for tularemia outbreaks

描述(由申请人提供)：虽然关于图拉氏方济氏菌的生物学已知很多，但调节其自然流行的因素仍未被描述。我们试图检验“现任规则”假说：通过与政治的类比，美国东北部的图拉氏F菌家畜受到与内生共生菌Francisella sp.的相互作用的限制。(以前归类为沃尔巴克氏菌属)在狗的组织中很常见，变色革螨。最近在玛莎葡萄园岛暴发的图拉热症提供了一个独特的机会，可以确定导致这种罕见感染传播增加的因素，因为那里的地点似乎是这种感染的长期自然疫源地。然而，验证这一假设需要确定这些自然疫源地，这些自然疫源地可能包括小片植被；传播并不均匀地分布在整个100,000公顷的岛屿上。因此，我们首先寻求通过(1)确定条纹臭鼬(Mephtis Mephtis)是否作为图拉氏丝虫传播的有效哨兵；以及(2)通过招募园艺师和其他职业暴露于图拉热病和其他扁虱传播感染的人积极实时报告工作中遇到的动物身体的存在，来补充基于臭鼬的预测，以确定此类自然疫源地。自然疫源地将通过密集的纵向动物流行病学分析(壁虱和其他潜在的媒介节肢动物感染图拉氏丝虫的流行率；啮齿动物和其他动物接触的证据)来确定。通过这种方式，我们将积累可靠的研究地点和全面检验“在任规则”假设所需的初步数据。此外，我们对危险地点的测绘可能会作为当地公共卫生措施的基础。我们预计，在拟议工作期间开发或验证的流行病学和流行病学方法可能有助于加强对图拉热病暴发的调查；为那些面临自然或非法图拉热症暴露风险的人提供新的预防策略；加强对环境中图拉氏菌的检测；并最终更好地了解图拉氏菌与宿主的相互作用。

DESCRIPTION (provided by the applicant): Although much is known about the biology of Francisella tularensis, the factors that regulate its natural prevalence remain un-described. We seek to test the 'rule of the incumbent' hypothesis: by analogy with politics, F. tularensis epizootics in the northeastern United States are limited by interactions with a 'ruling' endosymbiotic Francisella sp. (previously classified as Wolbachia sp.) common within tissues of dog ticks, Dermacentor variabilis. The recent outbreak of tularemia on Martha's Vineyard provides a unique opportunity for identifying factors that serve as the basis for increased transmission of this rare infection because sites there appear to be longstanding natural foci of this infection. However, testing this hypothesis requires identification of these natural foci, which may comprise small patches of vegetation; transmission is not homogeneously distributed over the entire 100,000-hectare island. Accordingly, we first seek to identify such natural foci by (1) determining whether striped skunks (Mephitis mephitis) serve as effective sentinels for F. tularensis transmission; and (2) complementing skunk-based predictions by enlisting landscapers and others who are occupationally exposed to tularemia and other tick borne infections to actively report, in real time, the presence of animal carcasses encountered during their work. Natural foci will be definitively confirmed by intensive longitudinal epizootiologic analyses (prevalence of F. tularensis infection in ticks and other potential vector arthropods; evidence of exposure in rodents and other animals). In this manner, we shall accumulate reliable study sites and the preliminary data required for a comprehensive test of the 'rule of the incumbent' hypothesis. In addition, our mapping of risky sites may serve as the basis for local public health measures. We anticipate that the epidemiologic and epizootiologic methods developed or validated during the proposed work may contribute towards enhanced investigations of tularemia outbreaks; new prevention strategies for those at risk of natural or illicit tularemia exposure; enhanced detection of F. tularensis in the environment; and, ultimately, a better understanding of F. tularensis-host interactions.