Manifestations and Management of Flea-Borne Rickettsioses

Abstract

Murine typhus and flea-borne spotted fever are undifferentiated febrile illnesses caused by Rickettsia typhi and Rickettsia felis , respectively. These organisms are small obligately intracellular bacteria and are transmitted to humans by fleas. Murine typhus is endemic to coastal areas of the tropics and subtropics (especially port cities), where rats are the primary mammalian host and rat fleas ( Xenopsylla cheopis ) are the vector. In the United States, a cycle of transmission involving opossums and cat fleas ( Ctenocephalides felis ) are the presumed reservoir and vector, respectively. The incidence and distribution of murine typhus appear to be increasing in endemic areas of the US. Rickettsia felis has also been reported throughout the world and is found within the ubiquitous cat flea. Flea-borne rickettsioses manifest as an undifferentiated febrile illness. Headache, malaise, and myalgia are frequent symptoms that accompany fever. The incidence of rash is variable, so its absence should not dissuade the clinician to consider a rickettsial illness as part of the differential diagnosis. When present, the rash is usually macular or papular. Although not a feature of murine typhus, eschar has been found in 12% of those with flea-borne spotted fever. Confirmatory laboratory diagnosis is usually obtained by serology; the indirect immunofluorescence assay is the serologic test of choice. Antibodies are seldom present during the first few days of illness. Thus, the diagnosis requires acute- and convalescent-phase specimens to document seroconversion or a four-fold increase in antibody titer. Since laboratory diagnosis is usually retrospective, when a flea-borne rickettsiosis is considered, empiric treatment should be initiated. The treatment of choice for both children and adults is doxycycline, which results in a swift and effective response. The following review is aimed to summarize the key clinical, epidemiological, ecological, diagnostic, and treatment aspects of flea-borne rickettsioses.

Is vertical transmission the only pathway for Rickettsia felis ?

“…Flea‐associated Rickettsiae represents one of the most neglected fields within rickettsiology (Blanton & Walker, 2017). Two groups are recognized: the Typhus group with a single species, Rickettsia typhi , the causal agent of endemic typhus, and the Transitional group, where Rickettsia asembonensis , Candidatus Rickettsia senegalensis (both nonpathogenic agents to date) and Rickettsia felis (species whose pathogenicity is under debate) are grouped (Blanton & Walker, 2017; Caravedo Martinez et al., 2021).…”

“…Rickettsia felis is the first agent described within the Transitional group in 1990 and has been isolated from the cat flea Ctenocephalides felis felis in Africa (Caravedo Martinez et al., 2021). This species represents a particular case because it has been detected using molecular methods in a wide range of arthropods, among which hematophagous groups, such as fleas and mosquitoes, stand out, as well as free‐living groups, such as booklice (Psocodea) and moths (Lepidoptera) (Behar et al., 2010; Brown & Macaluso, 2016; de Araújo et al., 2021; Parola et al., 2016).…”

Seroprevalence of Orientia tsutsugamushi and Rickettsia typhi in water buffaloes (Bubalus bubalis) from Southern Thailand

“…Trombiculid mites have been identified as possible vectors for O . tsutsugamushi transmission between hosts [ 23 ], and the rat flea ( Xenopsylla cheopis ) was identified as a significant vector species of R. typhi [ 3 ]. In addition, some reports by Sumrandee et al .…”

“…Both are neglected tropical zoonoses that are major causes of febrile illness worldwide [1,2]. Furthermore, both are transmitted through bites by their arthropod vectors, mainly ticks, followed by mites and fleas [3,4]. There are several reports on the incidence of both diseases in humans, animals, and arthropod vectors [5][6][7][8][9].…”

Salivary glands of the cat flea, Ctenocephalides felis: Dissection and microscopy guide

“…, hypersensitization of hosts to flea bites caused by certain compounds found in the cat flea's saliva ( Carlotti and Jacobs 2000 ; Contreras et al, 2018 ). Being a generalist blood-feeder, parasitizing a wide-range of potential hosts of zoonotic infections, the cat flea is capable of transmitting pathogenic microorganisms to humans, including Rickettsia felis and Rickettsia typhi (causing flea-borne spotted fever and murine typhus, respectively) ( Caravedo Martinez et al, 2021 ), Bartonella henselae (agent of cat-scratch fever) ( Sepúlveda-García et al, 2023 ), and potentially Yersinia pestis (causative bacterium of plague) ( Bland and Hinnebusch 2016 ). Moreover, the cat flea is an intermediate host of the tapeworm Dipylidium caninum , prevalent in pet populations and occasionally in children ( Elston and Do 2010 ).…”