Two Human Cases of Rickettsia felis Infection, Thailand (http://wwwnc.cdc.gov/eid/article/20/10/14-0905)

摘要

To the Editor: Rickettsia felis is an emerging pathogen responsible for fleaborne spotted fever. This new species was first isolated in 2002 from the cat flea, Ctenocephalides felis, which was then identified as the main vector of this rickettsia (1). R. felis has also been described in other flea, tick, chigger, and mite species (2) and more recently, in mosquitoes, which are strongly suspected to play a role in transmission of the bacterium (3,4). The first evidence of human pathogenicity of R. felis was suspected in a patient from Texas, USA, in 1991 and was confirmed by 3 additional case-patients from Mexico in 2000 (5). Evidence suggests that this bacterium has a worldwide distribution; ≈100 reports of human cases have been published (2,6). Moreover, R. felis was identified as a common (3%–15%) cause of fever among febrile patients in tropical Africa (7). The bacterium has also been described in Asia, but little is known about cases of infection in humans; only 1 human case was described in Thailand in 2003 (8). We enrolled febrile patients (>7 years of age) who came to 4 community hospitals, 2 in Chiang Rai (northern Thailand) and 2 in Khon Kaen (northeastern Thailand) during 2002–2005. Acute-phase and convalescent-phase (3–5 weeks later) serum samples were obtained from 2,225 patients and tested for R. felis by using an indirect immunofluorescence assay (9). Seventeen (0.8%) of 2,225 patients showed evidence of seroconversion (IgG titer ≥1:128 or IgM titer ≥1:64 or a ≥4-fold increase in titer).