Abstract：
The Asian longhorned tick (Haemaphysalis longicornis) was first reported in the United States in 2017 and has since been detected in at least 17 states. This tick infests cattle and can produce large populations quickly due to its parthenogenetic nature, leading to significant livestock mortalities and economic losses. While H. longicornis has not been detected in Texas, species distribution models have identified southern Texas as a possible hospitable region for this tick. Southern Texas is currently home to the southern cattle tick (Rhipicephalus microplus), which can transmit the causative agent of cattle fever (Babesia bovis). With the potential for H. longicornis and B. bovis to overlap in southern Texas and their potential to negatively impact the national and global livestock industry, it is imperative to identify the role H. longicornis may play in the cattle fever disease system. A controlled acquisition and transmission experiment tested whether H. longicornis is a vector for B. bovis, with the R. microplus-B. bovis system used as a positive control. Transstadial (nymphs to adults) and transovarial (adults to larvae) transmission and subsequent transstadial maintenance (nymphs and adults) routes were tested in this study. Acquisition-fed, splenectomized animals were used to increase the probability of tick infection. Acquisition nymphs were macerated whole and acquisition adults were dissected to remove midguts and ovaries at five time points (4, 6, 8, 10, and 12 days post-repletion), with 40 ticks processed per time point and life stage. The greatest percentage of nymphs with detectable B. bovis DNA occurred six days post-repletion (20.0 %). For adults, the percentage of positive midguts and ovaries increased as days post-repletion progressed, with day 12 having the highest percentage of positive samples (67.5 % and 60.0 %, respectively). When egg batches were tested in triplicate, all H. longicornis egg batches were negative for B. bovis, while all R. microplus egg batches were positive for B. bovis. During the transmission phase, the subsequent life stages for transstadial (adults) and transovarial transmission/transstadial maintenance (larvae, nymphs, and adults) were fed on naïve, splenectomized calves. All life stages of H. longicornis ticks tested during transmission were negative for B. bovis. Furthermore, the transmission fed animals were also negative for B. bovis and did not show signs of bovine babesiosis during the 45-day post tick transmission period. Given the lack of successful transstadial or transovarial transmission, it is unlikely that H. longicornis is a vector for B. bovis.
摘要：
亚洲长角蜱（Haemphysalislongicornis）于2017年在美国首次报道，此后至少在17个州被发现。这种蜱感染牛，由于其孤雌生殖的性质，可以迅速产生大量的种群，导致重大的牲畜死亡率和经济损失。虽然在德克萨斯州没有检测到H.longicornis，物种分布模型已将德克萨斯州南部确定为该tick的可能好客地区。得克萨斯州南部目前是南部牛tick（Rhipicephalusmicroplus）的所在地，可以传播牛发烧（Babesiabovis）的病原体。随着H.longicornis和B.bovis在德克萨斯州南部重叠的潜力，以及它们对国家和全球畜牧业产生负面影响的潜力，因此，必须明确长形目H.longicornis在牛发热疾病系统中可能发挥的作用。一个受控的采集和传输实验测试了H.longicornis是否是B.bovis的载体，与R.microplus-B.Bovis系统用作阳性对照。在这项研究中，测试了跨体育场（若虫到成虫）和跨血管（成虫到幼虫）传播以及随后的跨体育场维持（若虫和成虫）途径。收购，使用脾切除的动物来增加蜱感染的可能性。采集若虫被整体浸渍，采集成虫被解剖，以在五个时间点（补充后4、6、8、10和12天）去除内脏和卵巢，每个时间点和生命阶段处理40个蜱。具有可检测的牛芽孢杆菌DNA的若虫的最大百分比发生在补足后六天（20.0％）。对于成年人来说,随着补充后天数的进展，积极的中肠和卵巢的百分比增加，第12天的阳性样本百分比最高（67.5％和60.0％，分别)。当鸡蛋批次一式三份进行测试时，所有H.longicornis卵批次都对牛芽孢杆菌呈阴性，而所有R.microplus鸡蛋批次对牛芽孢杆菌呈阳性。在传输阶段,后继的生命阶段，为经stadial（成虫）和经varial传播/经stadial维持（幼虫，若虫,和成年人)被天真地喂养，脾切除的小牛。在传播过程中测试的所有生命阶段的H.longicornis壁虱对B.bovis均为阴性。此外，在蜱虫传播后的45天期间，饲喂传播的动物对牛B.bobis也呈阴性，并且没有显示牛babesiosis的迹象。鉴于缺乏成功的经房或经静脉曲张传播，不可能H.longicornis是B.bovis的载体。
