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.

Rickettsia felis（菲氏立克次体）是一类主要与猫栉首蚤（Ctenocephalides felis）相关的立克次体病原体。尽管实验室研究已证实，R. felis可通过猫栉首蚤的经变态传播（transstadial transmission）与经卵传播（transovarial transmission）在种群中维持，但猫栉首蚤间R. felis水平传播的具体机制仍未明确。鉴于猫栉首蚤对R. felis的垂直传播效率较低，且多种吸血节肢动物体内均检测到R. felis，本研究提出假说：R. felis可在猫栉首蚤间通过水平途径实现传播。为验证该假说，本研究连续四周每周评估了吸血过程中R. felis的蚤传播效应。在立克次体水平传播生物测定实验中，我们使用罗丹明B（Rhodamine B）区分未感染的受体蚤与感染R. felis的供体蚤，并采用实时定量PCR（quantitative real-time PCR）技术检测传播频率；同时通过免疫荧光试验（immunofluorescence assay）进一步确认了传播事件的发生。吸血24小时后，雌性蚤相较于雄性蚤更易通过感染R. felis的血餐获得感染（感染率分别为69.3%与43.3%）；且与感染R. felis的供体蚤共同饲养后，未感染的雌雄受体蚤均成功感染R. felis（感染率范围为3.3%~40.0%）。通过构建多组独立的生物测定体系，本研究进一步证实，R. felis可在共同饲养以及交配过程中从感染蚤传播至未感染蚤。本研究未观察到感染蚤对R. felis的垂直传播现象。本次研究证实猫栉首蚤间存在R. felis的水平传播，这一发现对菲氏立克次体病的生态学研究具有广泛的启示意义。