Data from: Horizontal transmission of Rickettsia felis between cat fleas, Ctenocephalides felis

Rickettsia felis is a rickettsial pathogen primarily associated with the cat flea, Ctenocephalides felis. Although laboratory studies have confirmed that R. felis is maintained by transstadial and transovarial transmission in C. felis, distinct mechanisms of horizontal transmission of R. felis among cat fleas is undefined. Based on the inefficient vertical transmission of R. felis by cat fleas and the detection of R. felis in a variety of hematophagous arthropods, we hypothesize that R. felis is horizontally transmitted between cat fleas. Towards testing this hypothesis, flea transmission of R. felis via a bloodmeal was assessed weekly for four weeks. Rhodamine B was used to distinguish uninfected recipient and R. felis-infected donor fleas in a rickettsial horizontal transmission bioassay and quantitative real-time PCR assay was utilized to measure transmission frequency; immunofluorescence assay also confirmed transmission. Female fleas acquired R. felis-infection more readily than male fleas after feeding on a R. felis-infected bloodmeal for 24 h (69.3% and 43.3%, respectively) and both Rickettsia-uninfected recipient male and female fleas became infected with R. felis after co-feeding with R. felis-infected donor fleas (3.3-40.0%). Distinct bioassays were developed to further determine that R. felis was transmitted from R. felis-infected to uninfected fleas during co-feeding and copulation. Vertical transmission of R. felis by infected fleas was not demonstrated in this study. The demonstration of horizontal transmission of R. felis between cat fleas has broad implications for the ecology of R. felis rickettsiosis.

菲氏立克次体（Rickettsia felis）是一种立克次体病原体，主要与猫栉首蚤（Ctenocephalides felis）相关联。虽然实验室研究已证实，菲氏立克次体可在猫栉首蚤体内经变态传播（transstadial transmission）与经卵传播（transovarial transmission）得以维持，但猫栉首蚤种群间菲氏立克次体的明确水平传播（horizontal transmission）机制仍未阐明。基于猫栉首蚤对菲氏立克次体的低效垂直传播（vertical transmission）现象，以及在多种吸血节肢动物中检出菲氏立克次体的研究基础，本研究提出假设：菲氏立克次体可在猫栉首蚤间通过水平途径实现传播。为验证上述假设，本研究连续四周每周评估了猫栉首蚤通过吸血餐传播菲氏立克次体的情况。本研究在立克次体水平传播生物测定试验中采用罗丹明B（Rhodamine B）区分未感染受体蚤与菲氏立克次体感染供体蚤，并通过实时定量聚合酶链反应（quantitative real-time PCR）测定传播频率；同时借助免疫荧光试验（immunofluorescence assay）验证了传播事件的发生。在取食感染菲氏立克次体的血餐24小时后，雌性猫栉首蚤的感染率（69.3%）显著高于雄性猫栉首蚤（43.3%）；且与感染菲氏立克次体的供体蚤共同饲养时，未感染立克次体的受体雌雄猫栉首蚤均会被菲氏立克次体感染，感染率范围为3.3%~40.0%。本研究通过独立设计的生物测定试验进一步证实，菲氏立克次体可在共同饲养与交配过程中，从感染个体传播至未感染个体。本研究未观测到感染猫栉首蚤通过垂直途径传播菲氏立克次体的现象。本次研究证实猫栉首蚤间存在菲氏立克次体的水平传播，该发现对菲氏立克次体立克次体病的生态学研究具有重要的学术意义。