Rickettsia felis, an Emerging Flea-Borne Rickettsiosis

Abstract

Rickettsia felis is an emerging insect-borne rickettsial pathogen and the causative agent of flea-borne spotted fever. First described as a human pathogen from the USA in 1991, R. felis is now identified throughout the world and considered a common cause of fever in Africa. The cosmopolitan distribution of this pathogen is credited to the equally widespread occurrence of cat fleas (Ctenocephalides felis), the primary vector and reservoir of R. felis. Although R. felis is a relatively new member of the pathogenic Rickettsia, limited knowledge of basic R. felis biology continues to hinder research progression of this unique bacterium. This is a comprehensive review examining what is known and unknown relative to R. felis transmission biology, epidemiology of the disease, and genetics, with an insight into areas of needed investigation.

Keywords: Epidemiology; Flea-borne spotted fever; Genetic diversity; Rickettsia felis; Transmission biology.

Fig. 1

The proposed and described transmission routes necessary for persistence and maintenance of R. felis infections within the environment. (A) Vertical non-transovarial transmission, i.e., larval acquisition by infectious adult feces, of R. felis within cat flea colonies requires experimental confirmation. (B) Adult acquisition bioassays with R. felis str. LSU and LSU-Lb resulted in infected cat fleas; however, acquisition bioassays with RFLOs have not been attempted. (C) Intraspecific transmission of R. felis between co-feeding cat fleas was demonstrated both in an artificial system and on a vertebrate host. (D) Interspecific transmission of R. felis between co-feeding cat fleas and rat fleas was observed on a vertebrate host. (E) Sustained transmission of R. felis by co-feeding was demonstrated by the continuous spread of infection to newly emerged uninfected cat fleas in an artificial system over the course of 4 weeks