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The distribution of hard ticks in Green Island: potential effects of habitat types and introduction of exotic sika deer
六次調查合計記錄到144堆梅花鹿排遺和採集到5,321隻游離硬蜱，包括成蜱124隻、若蜱636隻和幼蜱4,561隻，均屬於血蜱屬(Haemaphysalis spp.)種類。捕捉到126隻小型哺乳動物，分別為2隻溝鼠、24隻小黃腹鼠和100隻臭鼩並採集到48隻硬蜱，總帶硬蜱率為8.7%，其中可辨識種類的27隻硬蜱為粒形硬蜱(Ixodes granulatus)，其餘則均為硬蜱屬(Ixodes spp.)的種類。另外採集到271隻恙蟎，其中可辨識種類的134隻均屬於地里纖恙蟎(Leptotrombidium deliense)。熱點分析結果顯示島東邊的路邊樣線為游離硬蜱之熱點，其次為森林棲地。此外，梅花鹿排遺數與硬蜱數量沒有相關，但棲地類型(P< 0.01)與月份(P < 0.005)均會影響硬蜱數量，且彼此之間有顯著的交互作用(P < 0.001)：整體而言，硬蜱數量在三月與九月的森林和路邊樣線較高，在一月的三種棲地類型以及五、七、九、十一月的草地樣線，數量則是最低。
Several human diseases are transmitted by ticks, but there is a lack of studies on hard ticks in Green Island; moreover, past studies in Taiwan have focused on ticks collected from animal hosts, leaving the status of questing ticks unknown. In addition, sika deer (Cervus nippon) are introduced to Green Island and these feral deer might increase the number of ticks given that studies on other countries have demonstrated that deer are a major host of ticks. From January to December 2019, a total of 31 transects (100m x 1m) belonging to three types of habitat, including 9 grasslands, 11 forests, and 11 roadsides, were each dragged at both dawn and dusk to survey questing ticks every two months. Infested ectoparasites were also collected from trapped shrews and rodents in each transect. Lastly, the number of deer pellets observed in each site was deemed as an indicator of extent of deer activity. A total of 144 sika deer pellets and 5,321 Haemaphysalis ticks (124 adults, 636 nymphs and, 4,561 larvae) were recorded. Besides, a sum of 48 Ixodes ticks (27 I. granulatus and remaining unrecognizable Ixodes spp.) were collected from 126 rodents (2 Rattus norvegicus, 24 Rattus losea, 100 Suncus murinus), with 8.7% infestation rate. In addition, a total of 271 chigger mites were recovered, among which the 134 identified specimens were Leptotrombidium deliense. Spatial analyses revealed that roadside habitats in the eastern part of the island and forest habitats in the southern part of the island were the hotspots of ticks. There was no correlation between the number of deer pellets and number of ticks. However, tick abundance was affected by both habitat types (P< 0.01) and months (P < 0.005), and there was an interaction between both factors (P < 0.001). Tick abundance was higher in forest and roadside transects in March and September, but was lower in all habitat types in January, and grassland in May, July, September and November. This study provided a detailed description of variation of ticks across space and time in Green Inland and attempted to associate the variation with habitat types and exotic feral species. My next step is to confirm the tick species with molecular methods as well as assay the infective prevalence of Rickettsia spp. Overall, these results can contribute to a better understanding of human risks to tick-borne diseases in Green Island.
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