Shock Barbara C, Moncayo Abelardo, Cohen Sara, Mitchell Elizabeth A, Williamson Phillip C, Lopez Gaylord, Garrison Laurel E, Yabsley Michael J
Southeastern Cooperative Wildlife Disease Study, University of Georgia, Athens, GA, USA; Warnell School of Forestry and Natural Resources, University of Georgia, Athens, GA, USA.
Vector-Borne Diseases Section, Communicable and Environmental Diseases, Tennessee Department of Health, Nashville, TN, USA.
Ticks Tick Borne Dis. 2014 Jun;5(4):373-80. doi: 10.1016/j.ttbdis.2014.01.003. Epub 2014 Apr 6.
Piroplasms in the genera Babesia, Theileria, and Cytauxzoon are tick-borne parasites that may be animal and human pathogens. Most piroplasms with known life cycles are transmitted by ixodid ticks; however, for many species, the vector is unknown. This study was conducted to determine the prevalence and diversity of piroplasms in ticks from several US states. Piroplasm-specific polymerase chain reaction (PCR) assays were used to test 1631 ticks from Georgia (n=486), Kentucky (n=103), Pennsylvania (n=1), Tennessee (n=626), and Texas (n=414). Ticks were either questing (n=42) or collected from animals (n=627) or humans (n=962). The 2 primary species tested were Dermacentor variabilis (n=702) and Amblyomma americanum (n=743), but Amblyomma cajennense (n=99), Amblyomma maculatum (n=16), Ixodes scapularis (n=4), I. woodi (n=1), and unidentified Amblyomma spp. nymphs (n=64) were also tested. A low prevalence of piroplasms was detected with 37 (2.3%), 35 (2.1%), and 9 (0.6%) ticks positive for Theileria spp., Babesia spp., or Cytauxzoon felis, respectively. Based on sequence analysis, at least 6 Babesia spp. were detected and 15 of the 35 (41%) Babesia-positive ticks were A. americanum, 19 (56%) were D. variabilis, and one (3%) was an I. scapularis. Nine Babesia-positive ticks were removed from humans from Kentucky (n=1), Georgia (n=2), Texas (n=5), and Pennsylvania (n=1). Three Babesia-positive ticks were questing A. americanum which represents the first report of Babesia-infected questing Amblyomma in the US. Theileria infections were only detected in A. americanum, and all sequences were similar to white-tailed deer associated Theileria spp. C. felis was only detected in D. variabilis. These data suggest that A. americanum may be a vector of Babesia spp., although experimental studies are needed to confirm vector competence. Finally, these data demonstrate a high diversity of piroplasms in both questing and partially fed ticks in the US; although, host-blood meals can be present in non-questing ticks.
巴贝斯属、泰勒虫属和嗜吞噬细胞无形体属的梨形虫是蜱传播的寄生虫，可能是动物和人类病原体。大多数具有已知生命周期的梨形虫由硬蜱传播；然而，对于许多物种来说，传播媒介尚不清楚。本研究旨在确定美国几个州蜱中梨形虫的流行率和多样性。使用梨形虫特异性聚合酶链反应（PCR）检测法对来自佐治亚州（n = 486）、肯塔基州（n = 103）、宾夕法尼亚州（n = 1）、田纳西州（n = 626）和得克萨斯州（n = 414）的1631只蜱进行检测。蜱要么是正在寻找宿主的（n = 42），要么是从动物（n = 627）或人类（n = 962）身上采集的。检测的两种主要蜱种是变异革蜱（n = 702）和美洲钝缘蜱（n = 743），但也检测了卡延钝缘蜱（n = 99）、斑点钝缘蜱（n = 16）、肩突硬蜱（n = 4）、伍氏硬蜱（n = 1）以及未鉴定的美洲钝缘蜱若虫（n = 64）。检测到梨形虫的流行率较低，分别有37只（2.3%）、35只（2.1%）和9只（0.6%）蜱对泰勒虫属、巴贝斯属或嗜吞噬细胞无形体呈阳性。基于序列分析，至少检测到6种巴贝斯属物种，35只巴贝斯属阳性蜱中，15只（41%）是美洲钝缘蜱，19只（56%）是变异革蜱，1只（3%）是肩突硬蜱。从肯塔基州（n = 1）、佐治亚州（n = 2）、得克萨斯州（n = 5）和宾夕法尼亚州（n = 1）的人类身上采集到9只巴贝斯属阳性蜱。3只巴贝斯属阳性蜱是正在寻找宿主的美洲钝缘蜱，这是美国首次报告美洲钝缘蜱感染巴贝斯虫。仅在美洲钝缘蜱中检测到泰勒虫感染，所有序列均与白尾鹿相关的泰勒虫属相似。嗜吞噬细胞无形体仅在变异革蜱中检测到。这些数据表明，美洲钝缘蜱可能是巴贝斯属物种的传播媒介，不过需要进行实验研究来证实其传播能力。最后，这些数据表明在美国正在寻找宿主的蜱和部分饱血的蜱中梨形虫具有高度多样性；尽管未寻找宿主的蜱中可能存在宿主血餐。
