Abstract
BackgroundDespite increased identification of spotted fever group rickettsioses (SFGR) in animals and arthropods, human SFGR are poorly characterized in Taiwan.MethodsPatients with suspected Q fever, scrub typhus, murine typhus, leptospirosis, and dengue fever from April 2004 to December 2009 were retrospectively investigated for SFGR antibodies (Abs). Sera were screened for Rickettsia rickettsii Abs by indirect immunofluorescence antibody assay (IFA), and those with positive results were further examined for Abs against R. rickettsii, R. typhi, R. felis, R. conorii, and R. japonica using micro-immunofluorescence (MIF) tests. Polymerase chain reaction (PCR) for detection of SFGR DNA was applied in those indicated acute infections. Case geographic distribution was made by the geographic information system software.ResultsA total of 413 cases with paired serum, including 90 cases of Q fever, 47 cases of scrub typhus, 12 cases of murine typhus, 6 cases of leptospirosis, 3 cases of dengue fever, and 255 cases of unknown febrile diseases were investigated. Using IFA tests, a total of 49 cases with 47 (11.4%) and 4 (1.0%) cases had sera potentially positive for R. rickettsii IgG and IgM, respectively. In the 49 cases screened from IFA, MIF tests revealed that there were 5 cases of acute infections (3 possible R. felis and 2 undetermined SFGR) and 13 cases of past infections (3 possible R. felis and 10 undetermined SFGR). None of the 5 cases of acute infection had detectable SFGR DNA in the blood specimen by PCR. Possible acute infection of R. felis was identified in both one case of Q fever and scrub typhus. The geographic distribution of SFGR cases is similar with that of scrub typhus.ConclusionsHuman SFGR exist and are neglected diseases in southern Taiwan, particularly for the species closely-related to R. felis.
Highlights
Rickettsioses are a group of diseases that historically include rickettsial diseases, ehrlichiosis, anaplasmosis, scrub typhus, and Q fever, but Ehrlichia and Anaplasma were removed from the family Rickettsiaceae, Orientia from the genus, and Coxiella from alphaproteobacteria [1]
The aim of this study is to investigate the seroepidemiology of spotted fever group rickettsioses (SFGR) in patients who had suspected cases of Q fever, scrub typhus, murine typhus, leptospirosis, and dengue fever in southern Taiwan
Patients who were clinically suspected Q fever, scrub typhus, murine typhus, leptospirosis, and dengue fever were enrolled because these diseases are common zoonoses or arthropod-vectored diseases in Taiwan and are clinically difficult to differentiate them from SFGR
Summary
Rickettsioses are a group of diseases that historically include rickettsial diseases, ehrlichiosis, anaplasmosis, scrub typhus (caused by Orientia tsutsugamushi), and Q fever (caused by Coxiella burnetii), but Ehrlichia and Anaplasma were removed from the family Rickettsiaceae, Orientia from the genus, and Coxiella from alphaproteobacteria [1] These diseases are common zoonoses in humans that may present as a fever of unknown origin in clinical settings. Q fever, scrub typhus, and murine typhus are widely reported by clinicians in Taiwan [25,26,27,28,29,30,31], human SFGR infections have rarely been identified, except one imported human case of an African tick bite fever in 2009 (caused by R. africae) [32] and one indigenous R. felis infection in 2008 [33]. Despite increased identification of spotted fever group rickettsioses (SFGR) in animals and arthropods, human SFGR are poorly characterized in Taiwan
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