Kitaoka M, Asanuma K, Otsuji J
Am J Trop Med Hyg. 1974 Sep;23(5):993-9. doi: 10.4269/ajtmh.1974.23.993.
During the summer seasons of 1956 through 1970, 93 larval trombiculid mites were removed from 386 individuals who had been bitten by chiggers in Jumonji, Akita Prefecture. All 87 larvae that were available for examination were identified as Leptotrombidium akamushi. Infestation of man occurred predominantly during July and August, but the period extended from June to November. The duration of attachment was approximately 1 to 3 days. Usually only 1 chigger was found on a victim but on occasion as many as 7 were removed at one time. Scrub typhus developed in 45 (11.7%) of the 386 farmers bitten by chiggers. Although patients with scrub typhus may have sustained multiple bites, only one eschar was found. However, 76% of the patients did not recognize a bite either at the site where an eschar subsequently appeared or elsewhere prior to the onset of disease. If it is assumed that workers who did not subsequently become ill were equally unaware of chigger bites, then the probable incidence of disease in chigger victims was 3.1%. The minimum infectivity rate of L. akamushi larvae in Akita Prefecture was estimated to be 2.3%. Based upon the assumption that infection was transmitted as the result of a single bite, the infective rate of chiggers attacking man was calculated to be 2.5%.
在1956年至1970年的夏季，从秋田县十文字郡386名被恙螨叮咬的人身上采集到93只恙螨幼虫。所有87只可供检查的幼虫均被鉴定为红恙螨。人被恙螨感染主要发生在7月和8月，但感染期从6月持续到11月。恙螨附着时间约为1至3天。通常在一名受害者身上只发现1只恙螨，但有时一次能采集到多达7只。在386名被恙螨叮咬的农民中，有45人（11.7%）患了恙虫病。虽然恙虫病患者可能多次被叮咬，但仅发现一处焦痂。然而，76%的患者在焦痂出现部位或疾病发作前的其他部位均未察觉到被叮咬。如果假设后来未患病的工人同样未察觉到被恙螨叮咬，那么恙螨叮咬受害者的可能发病率为3.1%。秋田县红恙螨幼虫的最低感染率估计为2.3%。基于感染是由单次叮咬传播的假设，计算得出攻击人类的恙螨感染率为2.5%。
