Article

Two Pathogens and One Disease: Detection and Identification of Flea-Borne Rickettsiae in Areas Endemic for Murine Typhus in California

Division of Vector-borne Diseases, Vector-Borne Diseases, CDC, Atlanta, GA 30333, USA.
Journal of Medical Entomology (Impact Factor: 1.95). 11/2012; 49(6):1485-94. DOI: 10.1603/ME11291
Source: PubMed

ABSTRACT

Results of an environmental assessment conducted in a newly emergent focus of murine typhus in southern California are described. Opossums, Didelphis virginiana Kerr, infested with cat fleas, Ctenocephalides felis Buché, in the suburban area were abundant. Animal and flea specimens were tested for the DNA of two flea-borne rickettsiae, Rickettsia typhi and Rickettsia felis. R. felis was commonly detected in fleas collected throughout this area while R. typhi was found at a much lower prevalence in the vicinity of just 7 of 14 case-patient homes identified. DNA of R. felis, but not R. typhi, was detected in renal, hepatic, and pulmonary tissues of opossums. In contrast, there were no hematologic polymerase chain reaction findings of R. felis or R. typhi in opossums, rats, and cats within the endemic area studied. Our data suggest a significant probability of human exposure to R. felis in the area studied; however, disease caused by this agent is not recognized by the medical community and may be misdiagnosed as murine typhus using nondiscriminatory serologic methods.

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    • "In many cases, it is unclear if the pathogen is truly absent, or if absence is a result of undersampling (Yanagihara. 1990, Ellis et al. 1999, Inoue et al. 2008, Jiang et al. 2008, Eremeeva et al. 2012) and/or variability in disease detection methods (Klein et al. 2002, Jiang et al. 2008). When this uncertainty is coupled with the relative paucity of research on urban rats, the true distribution of rat-associated zoonoses becomes unclear. "
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    ABSTRACT: Urban Norway and black rats (Rattus norvegicus and Rattus rattus) are reservoirs for variety of zoonotic pathogens. Many of these pathogens, including Rickettsia typhi, Bartonella spp., and Seoul hantavirus (SEOV), are thought to be endemic in rat populations worldwide; however, past field research has found these organisms to be absent in certain rat populations. Rats (Rattus spp.) from an inner city neighborhood of Vancouver, Canada, were tested for exposure to and/or infection with SEOV and R. typhi (using serology and PCR), as well as Bartonella spp. (using culture and sequencing). Approximately 25% of 404 rats tested were infected with Bartonella tribocorum, which demonstrated significant geographic clustering within the study area. Infection was associated with both season and sexual maturity. Seroreactivity against R. typhi and SEOV was observed in 0.36% and 1.45% of 553 rats tested, respectively, although PCR screening results for these pathogens were negative, suggesting that they are not endemic in the study population. Overall, these results suggest that the geographic distribution of rat-associated zoonoses, including R. typhi, SEOV, and Bartonella spp., is less ubiquitous than previously appreciated, and is likely dependent on patterns of dispersion and establishment of the rat reservoir host. Further study on global and local Rattus spp. population structures may help to elucidate the ecology of zoonotic organisms in these species.
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    • "Its pathogenic role in humans has been demonstrated through PCR and serology in several cases, prevalently described in hot countries [6]. Typically, the disease presents as a flu-like acute febrile syndrome, very similar to murine typhus [7], associated with headache and rash. Other signs include: asthenia, myalgia, local lymphadenopathy, neurological signs, conjunctivitis, gastrointestinal involvement and cutaneous manifestations, such as generalized maculo-papular exanthema, and in some cases a characteristic inoculation eschar at the site of the flea bite; no fatalities have been reported [5],[8]–[10]. "
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    ABSTRACT: Rickettsia felis, the agent of flea-borne spotted fever, has a cosmopolitan distribution. Its pathogenic role in humans has been demonstrated through molecular and serologic tests in several cases. The cat flea (Ctenocephalides felis) is considered the main reservoir and the biological vector. The aim of this study was to assess the presence and occurrence of R. felis in fleas collected from dogs and cats in various sites of Palermo (Sicily). Between August and October 2012, 134 fleas were collected from 42 animals: 37 fleas from 13 dogs and 97 fleas from 29 cats. Two species of fleas were identified: 132 Ctenocephalides felis (98.51%) collected on all animals and only two C. canis (1.49%) on one dog. Out of 132 C. felis, 34 (25.76%), 12 from dogs (32.43%) and 22 (22.68%) from cats, were positive for R. felis DNA by a polymerase chain reaction (PCR), confirmed by sequencing. The only two C. canis fleas were negative. About half of examined animals (47.62%, 20/42) were infested with at least one infected flea; in particular 46.15% of dogs (6/13) and 48.28% of cats (14/29). It seems that in the Palermo district there is a peri-domestic cycle, with a relatively high prevalence of R. felis infection in the cat flea, an insect widely diffused in home environments and which can frequently bite humans. The results also suggest that R. felis should be considered in the human differential diagnosis of any spotted-like fever or febrile illness without a clear source of infection in Sicily, especially if the patient is known to have been exposed to flea bites.
    Full-text · Article · Sep 2014 · PLoS ONE
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    • "Prior to 2006, no flea-borne typhus infections had been reported in Orange County since 1991. The Orange County Vector Control District (OCVCD) collected only small numbers (< 5/yr.) of opossums, Didelphis virginiana Kerr, before the outbreak years, but expanded trapping efforts in recognition of this species' role as a significant host of the cat flea, Ctenocephalides felis Bouché, the primary flea-borne typhus vector in southern California and Texas (Adams et al. 1970, Sorvillo et al. 1993; Boostrom et al. 2002, Eremeeva et al. 2012). The purpose of this study was to develop an in-house ELISA with sera from opossums. "
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    ABSTRACT: The purpose of this study was to develop and validate an indirect enzyme linked immuno-assay (ELISA) for detection of antibodies in the Virginia opossum, Didelphis virginiana, to Rickettsia typhi and R. felis, the etiologic agents of flea-borne typhus. While ELISAs have proven to be highly sensitive and reliable for detecting infections from a variety of pathogens, no ELISAs are commercially available for testing many of the vertebrate species involved in flea-borne typhus transmission and enzootic maintenance. Under guidance from the Bacterial and Rickettsial Diseases Laboratory at the Walter Reed Army Institute of Research (WRAIR), the Orange County Vector Control District (District) received training and materials (protocols, antigens and controls) from WRAIR for developing the ELISA. District staff trapped opossums during ecologic investigations of human typhus cases, received opossums from public submissions and processed flea and blood samples from each animal for serologic and quantitative real-time polymerase chain reaction (qPCR) testing. Serologic data from the ELISA and qPCR results on fleas from their respective opossum hosts were compared and evaluated to identify the potential disease agent. Of 202 opossum sera evaluated by ELISA, 84 (41.6%) reacted to R. typhi antigen; qPCR testing of cat fleas (Ctenocephalides felis), the most abundant flea species on the opossums, yielded R. typhi and R. felis infection rates of < 1% and > 45%, respectively. Based on these data, it is probable that R. felis was the etiologic agent responsible for the seropositive reactions in the cross-reactive ELISA test. This hypothesis, however, could not be confirmed serologically due to the lack of R. felis-positive opossum control sera.
    Full-text · Conference Paper · Jan 2013
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