Takahashi M, Murata M, Machida K, Hori E, Kawamura A, Tanaka H
Department of Medical Zoology, Saitama Medical School, Japan.
Jpn J Exp Med. 1990 Dec;60(6):325-35.
In the epidemiological surveys on scrub typhus at Chichibu City near Tokyo, an area, 350 m by 35 m, in the Hitsujiyama Park was found to be heavily infested with Rickettsia tsutsugamushi (Rt). Distribution of trombiculid mites and their infection rates in this area were studied using sentinel animals, 48 Microtus montebelli and 10 ddY mice. The surveys were conducted 6 times in the autumn in 1985 and 1986. At the first 2 surveys, 16 animals were placed at random, and 4 restricted areas were identified as highly populated with trombiculid mites. For the detailed survey, each of 4 areas was divided into 2 m x 2 m quadrats to settle a sentinel animal to each. A total of mites collected by all sentinel animals was 331 Leptotrombidium pallidum, 175 L. fuji and 16 Gahrliepia saduski. Almost all mites were collected by M. montebelli, except only 1 L. fuji in 10 mice. From a M. montebelli in a quadrat, 157 L. pallidum were recovered, whereas the number/vole was 0 to 24 in the others. L. fuji was also highly aggregated at 2 sites. Rt was detected from individual mites by avidin-biotin immunofluorescence or isolated by the mouse passage from individual or pooled mites. Only Karp strain of Rt was detected or isolated from L. pallidum at a ratio of 31/286 (10.8%). No Rt was found from L. fuji or G. saduski. The infection rate in L. pallidum was especially high in 3 voles at ratios of 6/11, 2/5 and 3/5, respectively. Out of 14 sentinel M. montebelli with infected L. pallidum, 12 (85.7%) were infected with Rt. It was concluded that L. pallidum was distributed in aggregated clusters to form the mite islands and was infected heavily at the specific sites to make the infective spots.
在东京附近秩父市恙虫病的流行病学调查中，发现秩父市姬山公园内一块350米×35米的区域恙虫病东方体（Rt）感染严重。使用48只日本田鼠和10只ddY小鼠作为哨兵动物，研究了该区域恙螨的分布及其感染率。调查在1985年和1986年秋季进行了6次。在前两次调查中，随机放置了16只动物，确定了4个恙螨高密度分布的受限区域。为进行详细调查，将4个区域中的每个区域划分为2米×2米的样方，每个样方放置一只哨兵动物。所有哨兵动物收集到的恙螨总数为331只苍白纤恙螨、175只富士纤恙螨和16只佐渡嘉氏恙螨。几乎所有恙螨都是由日本田鼠收集到的，10只小鼠只收集到1只富士纤恙螨。从一个样方中的一只日本田鼠身上收集到157只苍白纤恙螨，而其他样方中每只田鼠收集到的数量为0至24只。富士纤恙螨在2个地点也高度聚集。通过抗生物素蛋白-生物素免疫荧光法从单个恙螨中检测到Rt，或通过将单个或合并的恙螨经小鼠传代分离出Rt。仅从苍白纤恙螨中检测到或分离出Karp株Rt，比例为31/286（10.8%）。未从富士纤恙螨或佐渡嘉氏恙螨中发现Rt。在3只田鼠身上，苍白纤恙螨的感染率特别高，分别为6/十一、2/五和3/五。在14只感染苍白纤恙螨的哨兵日本田鼠中，12只（85.7%）感染了Rt。得出的结论是，苍白纤恙螨呈聚集性分布形成螨岛，并在特定部位严重感染形成感染点。
