한국인에서의 Coxiella burnetii phase II 항원에 대한 항체보유에 관한 연구

Abstract

Background : Q fever is a worldwide zoonosis caused by Coxiella burnetii, and it manifests an influenza-like illness and pneumonia. Q fever was reported in more than 50 countries of five continents. In Asia, India, Saudi Arabia, Japan and China Q fever had already occurred. In Korea no outbreaks of Q fever have been reported yet, although some potentials of a Q fever outbreak has been suggested on the basis of epidemiologic background. As recently several cases of Q fever have been reported, seroepidemiological surveys to determine the prevalence of Coxiella burnetii infection among Koreans were done. But these surveys had limitations. That is to say, while immunoglobulins produced during acute phase of Q fever are mainly directed against the phase II antigen of the microorganism, these previous surveys were done with the phase I antigen, which is low titer during acute phase. Therefore to resolve this limitationn and evaluate the prevalence of Q fever in Korea more exactly, we conducted this serosurvey with the phase II antigen. Methods: We conducted a serosuvey for 58 stock breeders and 25 farmers who seemed to be a high ri나 group for the Coxiella burnetii infection and normal residents in a city. With use of an indirect immunofluorescent antibody test(IFA) employing the phase II antigen of the Nine-Mile strain of Coxiella burnetii, the titer of polyvalent immunoglobulins was determined. Results: 1) When IFA titer of 1:20 or above was considered seropositive, 23(39.7%) of 58 stock breeders and 12(48.0%) of 25 farmers were serpositive respectively. Fourteen(19.7%) of 71 city residents had elevated antibodies to the Coxiella burnetii phase II antigen. 2) IFA titers ranged from 1:20 to 1:320, but the majority of the seropositive samples showed IFA titers of 1:20 or 1:40 indicating that in a majority of the seropositves C. burnetii infection progressed weakly or antibody titer decreased because of the long duration after the infection. 3) As the age increased, a positive rate of antibody to Coxiella burnetii phase II antigen also increased. Conclusion : Our study suggests that Coxiella burnetii infection occurs in Korea more widely than expected and thus more extensive serosurvey and clinician's attentions for Q fever are required.