Steiner F E, Pinger R R, Vann C N
Department of Biology, Ball State University, Muncie, IN 47306, USA.
J Med Entomol. 1999 Nov;36(6):715-9. doi: 10.1093/jmedent/36.6.715.
To monitor the percentage and stability of Ehrlichia chaffeensis-infected ticks in southern Indiana over time, pools of Amblyomma americanum (L.) ticks were screened for infection in southern Indiana for a 2nd time. Nested polymerase chain reaction (with 6% DMSO included only in the 2nd reaction) was performed on 920 ticks in pools of 5 individuals from 9 sites (5 sites previously examined and 4 new ones) in 6 counties. The average minimum infection rate for all sites for 1997 was 1.6%, lower than that of 4.9% previously observed for 1995. However, when only the 5 sites that were positive for infected ticks in 1995 were reexamined, the average minimum infection rate was even more disparate (1.4% in 1997 and 5.1% in 1995). To correlate the presence of infected ticks with the presence of exposed deer, which serve as a reservoir, dried blood samples collected from hunter-killed deer at 2 locations in southern Indiana were tested for E. chaffeensis-reactive antibodies using an indirect immunofluorescent assay. Antibodies were detected in 45 and 47% of 98 samples examined from the 2 stations. These data provide support to our previous report of a population of E. chaffeensis-infected A. americanum in southern Indiana and the high proportion of deer previously exposed to E. chaffeensis suggests a stable maintenance of E. chaffeensis in this tick-vertebrate zoonotic system.
为了长期监测印第安纳州南部感染恰菲埃立克体的蜱虫的百分比及稳定性，对美洲钝缘蜱样本进行了第二次筛查。采用巢式聚合酶链反应（仅在第二轮反应中加入6%二甲亚砜），对来自6个县9个地点（5个为之前检测过的地点，4个为新地点）、每组5只蜱虫的920只蜱虫进行检测。1997年所有地点的平均最低感染率为1.6%，低于1995年之前观察到的4.9%。然而，仅对1995年发现有感染蜱虫的5个地点重新检测时，平均最低感染率差异更大（1997年为1.4%，1995年为5.1%）。为了将感染蜱虫的存在与作为宿主的暴露鹿的存在相关联，使用间接免疫荧光试验对从印第安纳州南部2个地点猎人捕杀的鹿身上采集的干血样本进行恰菲埃立克体反应性抗体检测。在从2个站点检测的98个样本中，分别有45%和47%检测到抗体。这些数据支持了我们之前关于印第安纳州南部存在感染恰菲埃立克体的美洲钝缘蜱种群的报告，并且之前暴露于恰菲埃立克体的鹿的高比例表明该立克次体在这个蜱 - 脊椎动物人畜共患病系统中稳定存在。
