Role of fleas in transmission of rickettsiae: ecology of flea-borne spotted fever

描述(申请人提供)：节肢动物是几种新出现和再次出现的传染病病原体的媒介，包括猫立克次体。自从首次在定殖化的猫蚤中被描述以来，费氏锥虫也作为一种人类病原体出现。要了解这种病原体的潜在风险，我们必须首先了解该生物体的生物学。我们的长期目标是描述跳蚤媒介在维持和传播自然界中的鼠疫杆菌中的作用。确定蚤类种群内的传播机制对于我们了解跳蚤传播斑点热的流行病学至关重要，并广泛影响我们采取控制措施的方法。拟议的研究将通过以下具体目标评估无脊椎动物和脊椎动物宿主在猫头蚤传播中的作用：(1)描述猫头蚤通过单个猫蚤和整个跳蚤种群传播的机制。将在受控制的实验室中测量菲氏跳蚤感染和传播的参数；具体地说，a)水平传播(脊椎动物宿主的贡献和同时摄食)；b)垂直传播(通过成体组织和生活史未成熟阶段的复制和传播的动态)；c)跳蚤适合度(繁殖率和羽化率)；以及d)性别比扭曲(对雄性和雌性比率的比较分析)；以及(2)通过评估脊椎动物宿主血粉和跳蚤种类对媒介能力的影响来研究跳蚤传播立克次体的生态学。拟议的研究将评估猫蚤在替代血粉来源存在的情况下对猫蚤的媒介能力，以及除猫蚤以外的其他跳蚤获取和传播猫蚤的能力。立克次体是由立克次体斑疹伤寒群和斑点热群成员引起的疾病。致病性立克次体通常通过节肢动物(昆虫和壁虱)传播给人类。该项目旨在研究猫立克次体和媒介蚤之间的相互作用，以更好地了解跳蚤传播斑点热的生态。

DESCRIPTION (provided by applicant): Arthropods serve as vectors for several emerging and reemerging infectious disease causing agents including Rickettsia felis. Since first being described in colonized cat fleas, R. felis has also emerged as a human pathogen. To understand the potential risk of this pathogen, we must first understand the biology of the organism. Our long-term objective is to delineate the role of the flea vector in the maintenance and transmission of R. felis in nature. Defining the mechanisms of transmission within populations of fleas is critical for our understanding of the epidemiology of flea-borne spotted fever and widely impacts our approach to control measures. The proposed studies will assess the role of invertebrate and vertebrate hosts in transmission of R. felis via the specific aims: (1) delineate the mechanisms by which R. felis spreads through individual cat fleas, Ctenocephalides felis, and throughout flea populations. Parameters of R. felis infection and transmission in fleas; specifically, a) horizontal transmission (contribution of vertebrate hosts and concurrent feeding); b) vertical transmission (dynamics of replication and dissemination through adult tissues and immature stages of life cycle); c) flea fitness (fecundity and eclosion rates); and d) sex ratio distortion (comparative analysis of male:female ratios) will be measured in a controlled laboratory R. felis/C. felis model; and (2) examine the ecology of flea-borne rickettsioses by assessing the influence of the vertebrate host bloodmeal and flea species on vector competence. Studies proposed will assess the vector competence of cat fleas for R. felis in the presence of alternate bloodmeal sources, as well as the competence of flea species other than cat fleas to acquire and transmit R. felis. Rickettsioses are diseases caused by members of the typhus group and spotted fever group of Rickettsia. Pathogenic Rickettsia are typically transmitted to humans by arthropods (insects and ticks). This project seeks to examine the interplay between Rickettsia felis and the vector flea, to better understand the ecology of flea-borne spotted fever.