ABSTRACT
Coxiella burnetii is the etiological agent of Q fever, that may occur either acutely or the chronically. To understand the seroepidemiological patterns of C. burnetii infection in Korea, we examined a total of 3,178 sera from patients with acute febrile episodes by using indirect immunofluorescence assay (IFA) for detectable antibodies to C. burnetii and other eight rickettsial antigens. The IFA seropositivity>or=1:20 for C. burnetii phase II was 11.5% (368 out of 3,178 sera). The co-existence of antibodies to other rickettsial antigens was found in 216 out of the 368 positive sera. Thirty-seven point five percent (n=138) had antibodies to R. tsutsugamushi (cutoff>or=1:20), 16% (n=59) to Ehrlichia sennetsu, 14.9% (n=55) to Rickettsia typhi, 13.5% (n=50) to R. akari, 11.4% (n=42) to R. japonica, 8.9% (n=33) to R. prowazekii, 7.6% (n=28) to R. sibirica, and 6.7% (n=25) to R. conorii by IFA, respectively. These results are consistent with previous reports documenting diverse serum cross-reactivity in chronic Q fever. Therefore we excluded the samples that reacted to other rickettsial antigens at same or higher titers than to C. burnetii, resulting in the seropositive rate of 4.1%. The serological prevalence was 2% (n=64) when the conventional cut-off titer of 1:80 was used. Our results suggest that infections with C. burnetii are more prevalent than expected previously and should be differentially diagnosised for febrile illness occurring after exposure to ticks or other vectors.
Subject(s)
Humans , Antibodies , Coxiella burnetii , Coxiella , Diagnosis , Fluorescent Antibody Technique, Indirect , Korea , Neorickettsia sennetsu , Prevalence , Q Fever , Rickettsia , Rickettsia typhi , Seroepidemiologic Studies , TicksABSTRACT
Eight Borrelia burgdorferi strains, which had been isolated from Ixodes nipponensis and Apodemus agrarius captured in the Chungju area of Korea, were characterized by ospC gene sequence analysis. Nucleotide sequence similarity among the Chungju strains ranged from 83.6 to 100%. Deduced amino acid sequence similarity of the Chungju strains ranged from 75.4 to 100%. In a molecular phylogenetic analysis, the Chungju strains were separated from B. burgdorferi and B. garinii reference strains, and formed a cluster with B. afzelii reference strains. Three (KK2, KM4, and KK5), two (CJ2 and CJ21), and one (CJ3) Chungju strains formed clusters with OspC serotype 5, OspC serotype 8, and OspC serotype 7 reference strains, respectively. However, two Chungju strains (KK1 and KM10) formed a distinctive cluster that was separated from other strains of B. afzelii reference strains. These results suggest that Chungju strains are very heterogeneous in clonality.
Subject(s)
Animals , Amino Acid Sequence , Base Sequence , Borrelia burgdorferi Group , Borrelia burgdorferi , Borrelia , Genetic Heterogeneity , Ixodes , Korea , Murinae , Sequence AnalysisABSTRACT
Ehrlichia sennetsu is the causative agent of human Sennetsu ehrlichiosis. Ehrlichiosis is an acute and occasionally chronic infectious disease caused by obligate intracellular bacteria in the family Rickettsiaceae. To understand the seroepidemiological patterns of ehrlichiosis in Korea, a total of 2,625 patients with acute febrile episode reported from 1990 to 1992 were surveyed using an indirect fluorescent antibody assay (IFA). The result was as follows. Seropositivity for ehrlichiosis was 3.23% by excluding highly cross-reacted sera with other rickettsial antigens. Sera reacted to E. sennetsu showed the cross reaction with other rickettsia as in the order of R. typhi 49.6%, R. conorii 31.6%, R. japonica 28.1%, C. burnetii 26.4%, R. sibirica 25.8%, O. tsutsugamushi 25.8%, R. akari 25.4%, and R. prowazekii 25.4%. Sexual difference in the seropositivity was not noted. The age groups of fifties and under the tenth showed higher prevalence than others. Seropositivity was most prevalent in July and August. As for regional distribution, Chonbuk (10.5%) showed the highest seropositive rate. Geographical distribution of the seropositivity covered most area except Cheju province in Korea.