Ecology of Rickettsia felis: a review

Abstract

It has been two decades since the first description of Rickettsia felis, and although a nearly cosmopolitan distribution is now apparent, much of the ecology of this unique microorganism remains unresolved. The cat flea, Ctenocephalides felis, is currently the only known biological vector of R. felis; however, molecular evidence of R. felis in other species of fleas as well as in ticks and mites suggests a variety of arthropod hosts. Studies examining the transmission of R. felis using colonized cat fleas have shown stable vertical transmission but not horizontal transmission. Likewise, serological and molecular tools have been used to detect R. felis in a number of vertebrate hosts, including humans, in the absence of a clear mechanism of horizontal transmission. Considered an emerging flea-borne rickettsiosis, clinical manifestation of R. felis infection in humans, including, fever, rash, and headache is similar to other rickettsial diseases. Recent advances toward further understanding the ecology of R. felis have been facilitated by stable R. felis-infected cat flea colonies, several primary flea isolates and sustained maintenance of R. felis in cell culture systems, and highly sensitive quantitative molecular assays. Here, we provide a synopsis of R. felis including the known distribution and arthropods infected; transmission mechanisms; current understanding of vertebrate infection and human disease; and the tools available to further examine R. felis.

Fig. 1.

Reported distribution of R. felis. R. felis–positive arthropods have been identified in the following countries (gray): Afghanistan, Algeria, Argentina, Australia, Canada, Chile, Croatia, Cyprus, Democratic Republic of Congo, Ethiopia, Gabon, Indonesia, Israel, Japan, New Zealand, Peru, Portugal, United Kingdom, and Uruguay. R. felis–positive arthropods and cases of flea-borne spotted fever have been identified in the following countries (black): Brazil, Egypt,* France, Germany, Laos, Mexico, South Korea, Spain, Taiwan, Thailand, Tunisia,* and the United States (*not reported from arthropods in this country).