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Molecular and seroepidemiological study of Q fever in the Democratic Republic of Sao Tome and Principe
Q fever,Coxiella burnetii,Democratic Republic of Sao Tome and Principe,seroprevalence,dried blood spots,ticks,
|Publication Year :||2017|
|Abstract:||Q熱是一種世界性人畜共通傳染病，病原體為貝氏考克斯菌 (Coxiella burnetii, C. b.)，同時也被視為現今新興與再興傳染病之一。然而，Q熱在非洲盛行之情況仍未被充分了解，而病原體之分子檢驗更是有限。本研究調查聖多美普林西比民主共和國 (簡稱聖國) 的Q熱盛行情況，並藉由分析當地家畜牛羊身上寄生之蜱以探討其暴露貝氏考克斯菌之可能，同時分析當地蜱族群似考克斯菌屬之內共生菌之特性。於2016年一月至三月，在聖國大水省收集的18,113位一般民眾之乾燥濾紙血片檢體，將其年齡分層界定為0至5歲、6至15歲、16至25歲等到56至65歲以及超過65歲共八個年齡層，從各年齡層隨機選取30個檢體，共240個檢體樣本。使用間接免疫螢光分析方法進行血清學分析。結果顯示血清IgG效價達1:50 之陽性率為6.7% (16/240)，陽性個案來自各年齡層，未偵測到IgM檢體。蜱種則採集自聖多美島之牛和羊，採樣時間分別是2012年1月及2016年7至8月。蜱種型態鑑定分別為星狀花蜱 (Amblyomma astrion; A. a.) 42隻，及變異花蜱 (Amblyomma vareigatum; A. v.) 60隻，以聚合酶鏈鎖反應 (PCR) 偵測貝氏考克斯菌之超氧化物歧化酶基因 (sod) 和轉位子核酸序列 (IS1111)，以及考克斯菌屬之16S核醣體RNA基因，結果均未偵測到蜱蟲體內攜帶貝氏考克斯菌。然而，考克斯菌屬的16S核醣體基因序列分析結果，顯示似考克斯菌屬之共生菌確實存在於聖國之蜱體內，變異花蜱序列與已發表的A. v.體內之似考克斯菌屬之內共生菌16S核醣體基因序列相似度為99.9%；星狀花蜱則尚無16S核醣體基因序列資料。本研究證實了聖國一般民眾的Q熱血清盛行形況，並針對當地家畜牛羊暴露貝氏考克斯菌的可能進行首次評估。然而，聖國Q熱的傳播情境和機制尚待進一步釐清。|
Q fever is a worldwide zoonotic disease caused by Coxiella burnetii and considered as an emerging and re-emerging infectious disease. However, the knowledge of Q fever in Africa is quite deficient and the molecular evidence was limited as well. This study was aimed to investigate the seroprevalence of Q fever in the Democratic Republic of Sao Tome and Principe (DRSTP) and the possible exposure to C. burnetii among local flocks of domestic cattle and goats by analysis on the ticks infesting them, and was also intended to demonstrate the existence of Coxiella-like endosymbionts in the DRSTP tick population. For the 18,113 dried blood spot samples collected from the generally healthy people in Agua Grande District, DRSTP between January and March 2016, age-grouping by 10 years above 5 and random selection of 30 samples among each age group was applied. Total 240 human samples from 8 age groups were tested for antibodies of IgG and IgM against C. burnetii phaseⅡby immunofluorescence assay. The overall seropositive rate at the titer of 1:50 was 6.7% (16/240) and the seropositive cases were at the age ranging from three to over 65 years. Ticks were removed from goats and cattle raised on Sao Tome island in January 2012 and during July to August 2016 separately. After morphological and molecular identification of tick species, Amblomma astrion and Amblyomma variegatum were identified. Ticks were detected for C. burnetii gene sod and IS1111 and 16S rRNA gene of Coxiella bacteria. Among the 102 ticks, none of the ticks were positive by PCR using sod and IS1111. However, the Coxiella 16S rRNA gene sequences detected in A. variegatum were comparable to other published findings of Coxiella-like endosymbionts reported from A. variegatum with identities of 99.9%; as for the A. astrion, data of Coxiella 16S rRNA gene sequences had no record so far. In conclusion, this study found serological evidence in local general residents and evaluated the exposure to C. burnetii among domestic ruminants in this country for the first time. Nevertheless, possible transmissions between livestock and human were unclear so far in the DRSTP and needed to be identified in the further investigation.
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