The significance of birds as the hosts of ticks and the role of migratory birds in the dispersal of tick-borne diseases

世界上正出現許多，由硬蜱(ticks)這類外寄生蟲所傳播的人類新興疾病。由於野生動物的物種組成會決定硬蜱的數量與硬蜱會傳播的疾病，獲知哪些野生動物對於硬蜱族群的存續較為重要，具有公共衛生上的意義。鳥類為硬蜱主要的動物宿主之一，且候鳥可能會藉由攜帶硬蜱，在不同國家間傳播疾病。然而過去台灣有關硬蜱或硬蜱傳播疾病的研究，僅著重在哺乳類這類群宿主上，忽略了鳥類對於硬蜱的可能影響。本研究於2014年九月至2016年四月，在臺灣七個樣點，捕捉留鳥以及候鳥以採集鳥類身上的硬蜱，同時收集其他研究人員過去採集到的硬蜱樣本。之後藉由外部型態與分子檢測的方式鑑定硬蜱的種類，同時檢測硬蜱身上是否感染有病原體。七個樣點總共調查56次，最後捕捉到86種鳥類，3062隻個體，4145隻次，包括59種留鳥與27種候鳥。利用霧網捕捉，加上收集其他研究者過去的採集樣本，總共由130隻硬蜱鑑定出12種，包括五種過去臺灣未曾記錄過的種類與一種過去不確定是否在臺灣採集過的種類；另外包括過去經常可在嚙齒類動物身上採到的兩種硬蜱。病原體的部份，總共檢測出三種Borrelia，三種Rickettsia，一種Anaplasma，一種Ehrlichia，一種Devosia，與一種Babesia的品系，其中包括一種由候鳥身上硬蜱檢測到，已知會對人造成危害，但過去未曾在臺灣記錄過的Borrelia品系。本研究結果顯示研究鳥類，包括候鳥，攜帶的硬蜱對於瞭解硬蜱傳播疾病在臺灣的流行狀況有相當程度的助益。

A variety of human diseases transmitted by arthropod vectors, including ticks, are emerging around the globe. Because the composition of wildlife host species can determine the abundance of ticks as well as the diseases they can transmit, assessing the relative importance of potential wildlife hosts to the subsistence of ticks are valuable for the prevention of infectious diseases. Birds are known to be one of the primary hosts of ticks and migratory birds can help disperse exotic ticks and tick-borne diseases. In Taiwan, however, past studies have mainly focused on mammals, leaving the role of birds in the subsistence of ticks undetermined. In this study, ticks were collected from both migratory and resident birds from several sources, including from birds mist-netted in seven study sites between September 2014 and April 2016 and from birds handled by other experts. Tick species were later identified based on both morphological and molecular information, and potential pathogens were detected in these ticks. The seven study sites were surveyed for a sum of 56 times, with 4145 captures of 3062 unique individuals of 86 bird species. These included 59 resident species and 27 migratory bird species. Based on ticks collected from mist-netted birds and specimens collected by other researchers, a total of 130 ticks belonging to at least 12 species were recovered, including five species not recorded and one species unconfirmed in Taiwan before. The tick fauna also includes two species commonly recovered from rodents. At least three Borrelia strains, three Rickettsia strains, one Anaplasma strain, one Ehrlichia strain, one Devosia strain, and one Babesia strain were successfully sequenced from ticks. Moreover, a Borrelia strain potentially pathogenic to humans was detected in ticks of migratory birds for the first time in Taiwan. Results of this study emphasize the importance of studying ticks in birds to help assess current and further status of tick-borne diseases in Taiwan.