Transmission potential of Rickettsia felis infection by Anopheles gambiae mosquitoes

Abstract

A growing number of recent reports have implicated Rickettsia felis as a human pathogen, paralleling the increasing detection of R. felis in arthropod hosts across the globe, primarily in fleas. Here Anopheles gambiae mosquitoes, the primary malarial vectors in subSaharan Africa, were fed with either blood meal infected with R. felis or infected cellular media administered in membrane feeding systems. In addition, a group of mosquitoes was fed on R. felisinfected BALB/c mice. The acquisition and persistence of R. felis in mosquitoes was demonstrated by quantitative PCR detection of the bacteria up to day 15 postinfection. R. felis was detected in mosquito feces up to day 14. Furthermore, R. felis was visualized by immunofluorescence in salivary glands, in and around the gut, and in the ovaries, although no vertical transmission was observed. R. felis was also found in the cotton used for sucrose feeding after the mosquitoes were fed infected blood. Natural bites from R. felisinfected An. gambiae were able to cause transient rickettsemias in mice, indicating that this mosquito species has the potential to be a vector of R. felis infection. This is particularly important given the recent report of high prevalence of R. felis infection in patients with "fever of unknown origin" in malaria-endemic areas.Rickettsia felis | spotted fever | Anopheles gambiae I n 2002, Rickettsia felis, an obligate intracellular bacterium that belongs to the spotted fever group of Rickettsia, was definitively described (1, 2). Over the past 2 decades, an increasing number of reports have implicated R. felis as a human pathogen, paralleling an increase in reports of the detection of R. felis in arthropod hosts throughout the world (1, 3).By 2011, more than 70 human cases of R. felis had been reported worldwide, including in Central and South America, Asia, northern Africa, and Europe (1). More cases have been published since then, including the first probable human cases in Australia (4). In sub-Saharan Africa, recent studies have challenged the importance of R. felis infection in patients with "fever of unknown origin," with this bacterium detected in up to 15% of such patients (5-7). In 2011, a potential R. felis primary infection, called "yaaf," was suspected in the case of an 8-mo-old girl in Senegal with polymorphous skin lesions similar to those seen in patients from Mexico (8). The epidemiologic and clinical picture of this emerging infection in Africa, including its potential vectors, is poorly understood, however.Various arthropods, but primarily fleas, have been associated with R. felis (1, 3). More specifically, the cat flea Ctenocephalides felis is the arthropod in which R. felis has been most frequently detected. To date, it is the sole confirmed biological vector of R. felis, with both horizontal and vertical transmission making this flea a potential reservoir for this bacterium (9-11). However, in some countries where R. felis appears to be highly prevalent, such as Senegal, neither cat fleas nor other arthropods have been...

Reply to Slesak et al.: So much about Rickettsia felis infection to be discovered

“…(1) on our work (2), and agree that the number of animals, including leeches and arthropods, playing a role in the transmission of Rickettsia felis might be greater than previously suspected. In the Slesak et al…”

Cofeeding intra‐ and interspecific transmission of an emerging insect‐borne rickettsial pathogen

“…Moreover, R. felis has been identified by molecular detection from the blood, skin, and internal organs of suspected reservoir hosts (Abramowicz et al 2011; Kuo et al 2015; Panti-May et al 2014; Schriefer et al 1994b; Tay et al 2015; Tay et al 2014), but viable bacteria have never been isolated from these tissues. A recent study generated R. felis -infected mice (inbred mouse strain BALB/c) via an artificial inoculation route, and subsequently produced infectious Anopheles gambiae mosquitoes that caused transient rickettsemia in naïve mice (Dieme et al 2015); however, naturally infected mammalian blood or tissues have never been shown to be a source of R. felis infection from vertebrate to arthropod host (Weinert et al 2009). Additionally, much debate surrounds the likelihood of freely circulating rickettsiae in the blood of vertebrates from non-fatal cases (Labruna & Walker 2014).…”

Rickettsia felis Infection in Febrile Children, Ghana

“…4 Similar age and seasonality patterns of infection, along with the recently reported potential of Anopheles gambiae mosquitoes to transmit R. felis, have given rise to a new hypothesis on possible common transmission routes of R. felis and malaria. 4,5,13 The clinical significance of R. felis infection and malaria-R. felis coinfection has been controversially discussed. In our study, all patients were febrile, but additional symptoms were nonspecific.…”