台灣金門地區小型哺乳動物及外寄生蜱蟲攜帶無形體、艾利希氏體及其他蜱媒微生物之檢測

Abstract

根據衛福部疾管署的統計數據，2013年至2022年間，全國通報為恙蟲病的疑似病例累積達2.7萬例，其中僅有4,100例確診，發生率為每10萬人年1.8例。值得注意的是，近七成確診病例來自花東及離島地區，其中金門縣發生率高達每10萬人年25.2例，確診率僅47%。此外，2019年一項回溯性研究提出，金門通報為疑似恙蟲病患者之血液樣本經分子診斷後，除確診為恙蟲病，還同時感染了由蜱蟲所傳播的嗜吞噬球無形體，這表明金門可能存在恙蟎以外的病媒和病原體。蜱蟲為吸血性體外寄生蟲，通過叮咬和吸食宿主血液，將病原體跨蟲期傳播給動物宿主，從而成為人類及人畜共通傳染病的重要病媒。金門的離島生態環境豐富多樣，棲地適合生物生長，加上其地理位置位於中國與台灣之間的重要交通樞紐，貿易與旅遊的來往頻繁，使得疾病傳播得更為迅速和廣泛。為了更全面了解金門地區小型哺乳動物和蜱蟲的地理分布、物種多樣性、蜱媒病原體的流行情況以及其與不明熱的關聯性，本研究於2018年8月至2022年6月在金門地區進行了小型哺乳動物誘捕之長期調查。所採集小型哺乳動物及蜱蟲以形態及分子檢驗鑑定物種，並檢測其所攜帶病原體包含嗜吞噬球無形體、艾利希氏體及新艾利希氏體的情況。調查期間於金門本島的金寧鄉、金城鎮及金湖鎮共捕獲了692 隻小型哺乳動物，涵蓋小黃腹鼠、亞洲家鼠、家鼷鼠、溝鼠、赤腹松鼠及臭鼩共六個物種，其中以小黃腹鼠為主要優勢種，並收集928隻外寄生蜱蟲，鑑定為粒形硬蜱及鐮形扇頭蜱共兩個物種。隨機挑選62隻小型哺乳動物的脾臟組織及其外寄生的200隻粒形硬蜱進行DNA萃取，利用聚合酶連鎖反應(PCR)技術增幅無形體科之16S rDNA片段基因。分子檢驗結果顯示，小型哺乳類動物脾臟組織無形體基因序列和過去於金門縣小黃腹鼠檢測出的嗜吞噬球無形體(Accession no.: MK394178.1) 100%相似(n=10)、99.67% 相似(n=1)、99.58% 相似(n=1)，陽性率為19.4% (12/62)，而新艾利希氏體基因序列和中國廣州市小黃腹鼠所檢測出的 Neoehrlichia mikurensis (Accession no.: MH722225.1) 100%相似(n=4)、99.67% 相似(n=1)，陽性率為 8.1% (5/62)，艾利希氏體則未檢測出。粒形硬蜱無形體基因序列和過去於金門縣小黃腹鼠檢測出的嗜吞噬細胞無形體(Accession no.: MK394178.1) 100%相似，陽性率為 2.0% (4/200)，艾利希氏體基因序列和日本沖繩縣粒形硬蜱檢測出的Ehrlichia sp. 360 (Accession no.: AB428564.1)一致，陽性率為 42.5% (85/200)，而新艾利希氏體基因序列和中國廣州市小黃腹鼠所檢測出Neoehrlichia mikurensis (Accession no.: MH722225.1) 100% 相似，陽性率為 8.5% (17/200)。綜合以上，在金門本島金寧鄉、金城鎮及金湖鎮三個城鎮中，小黃腹鼠脾臟檢測出致病性嗜吞噬球無形體之陽性率分別為，17.2%、27.3%、9.1%，另一病原體Neoehrlichia mikurensis之陽性率分別為13.8%、4.5%、0%。粒形硬蜱感染嗜吞噬球無形體之陽性率則分別為1.0%、3.8%、0%，Ehrlichia sp. 360 之陽性率分別44.6%、42.3%、33.3%，Neoehrlichia mikurensis之陽性率分別為9.9%、6.4%、9.5%。顯示金門地區的民眾具有可能感染蜱媒傳染病的風險。健康一體 (One Health) 涵蓋了人類、動物與環境健康的交互作用，透過長期、定期監測調查及病原體檢測，釐清不明熱症狀來源的潛在關係，將有助於評估金門地區流行情形並對於蜱媒不明熱流行病診斷之參考。

According to the statistics from the Taiwan Centers for Disease Control (CDC), from 2013 to 2022, there were 27,000 notified cases of suspected scrub typhus due to unknown fever symptoms nationwide, but only 4,100 cases were confirmed, resulting in an incidence rate of 1.8 cases per 100,000 person-years. Analyzing the distribution across various counties, the number of confirmed cases was concentrated in outlying island areas, with Kinmen County exhibiting a particularly high incidence rate of 25.2 cases per 100,000 person-years and a confirmation rate of only 47%. Additionally, a retrospective study in 2019 revealed that blood samples from suspected scrub typhus patients in Kinmen, when subjected to molecular diagnostics, showed co-infection with Anaplasma phagocytophilum, a pathogen transmitted by ticks, indicating the possible presence of vectors or pathogens other than chiggers in Kinmen area. Ticks are obligatory hematophagous ectoparasites and some pathogens can be transmitted through transstadial transmission making ticks significant vectors of zoonotic diseases and a major global public health threat. The diverse and rich ecological environment of Kinmen, coupled with its strategic geographic location as a major transportation hub between China and Taiwan, facilitates frequent trade and travel, thus accelerating the spread of diseases. To gain a comprehensive understanding of the geographic distribution, species diversity, prevalence of tick-borne pathogens, and their association with febrile illnesses in small mammals and ticks in Kinmen, a long-term survey was conducted from August 2018 to June 2022. Total genomic DNA was extracted from the spleen and individual ticks from captured small mammals. PCR with primer sets of 16S rDNA gene were used to detect Anaplasma, Ehrlichia, and Neoehrlichia spp. During the survey, 692 small mammals were captured across Jinning Township, Jincheng Township, and Jinhu Township around Kinmen area, belonging to five species of rodents (Callosciurus erythraeus, Mus musculus, Rattus losea, Rattus norvegicus, and Rattus tanezum) and one species of Suncus murinus were identified. Additionally, 928 ectoparasitic ticks were collected from 208 small mammals, and identified as two species: Ixodes granulatus and Rhipicephalus haemaphysaloides. A total of 62 spleen samples and 200 ticks from 89 small mammals were investigated for potential Anaplasmataceae pathogens by PCR. The sequencing results showed that Anaplasmataceae sequences from the spleen tissues of small mammals were 100% (n=10), 99.67% (n=1), and 99.58% (n=1) identical to Anaplasma phagocytophilum detected in Rattus losea from Kinmen County (Accession no.: MK394178.1), with the positive rate was 19.4% (12/62). The sequences of Neoehrlichia mikurensis were 100% (n=4) and 99.67% (n=1) identical to those detected in Rattus losea in Guangzhou, China (Accession no.: MH722225.1), with the positive rate was 8.1% (5/62), while no Ehrlichia species were detected from the spleen tissues of small mammals. For Ixodes granulatus ticks, the Anaplasmataceae sequences were 100% identical to Anaplasma phagocytophilum detected in Rattus losea in Kinmen County (Accession no.: MK394178.1), with a positive rate was 2.0% (4/200). The sequences of Ehrlichia were identical to Ehrlichia sp. 360 detected in Ixodes granulatus ticks in Okinawa, Japan (Accession no.: AB428564.1), with a positive rate was 42.5% (85/200). The sequences of Neoehrlichia mikurensis were 100% identical to those detected in Rattus losea in Guangzhou, China (Accession no.: MH722225.1), with a positive rate was 8.5% (17/200). In summary, the prevalence of pathogenic Anaplasma phagocytophilum in the spleen of Rattus losea from Jinning Township, Jincheng Township, and Jinhu Township was 17.2%, 27.3%, and 9.1%, respectively, while the prevalence of Neoehrlichia mikurensis was 13.8%, 4.5%, and 0%. The prevalence of Anaplasma phagocytophilum in Ixodes granulatus ticks was 1.0%, 3.8%, and 0%, respectively; for Ehrlichia sp. 360, it was 44.6%, 42.3%, and 33.3%; and for Neoehrlichia mikurensis, it was 9.9%, 6.4%, and 9.5%. These findings indicate a potential risk of tick-borne diseases for the residents of Kinmen. The One Health approach, which encompasses the interaction of human, animal, and environmental health, emphasizes the importance of long-term, regular surveillance and pathogen detection, which can help clarify the sources of unknown fever symptoms and provide valuable insights for the diagnosis of tick-borne febrile illnesses in Kinmen area.