Endris R G, Haslett T M, Birnie E F, Hess W R
USDA-ARS, Plum Island Animal Disease Center, Greenport, NY 11944.
Vet Microbiol. 1989 Feb;19(2):151-65. doi: 10.1016/0378-1135(89)90080-1.
A mouse lethal dose assay was used to detect a mouse pathogenic strain (Kwanyanga) of Cowdria ruminantium, the etiological agent of heartwater in goats and ticks. The titer of the rickettsial organisms in goat blood was directly related to the febrile response of the goat and the rickettsia were undetectable after the fever subsided. The maximum rickettsial titer in goat blood was 10(3) mouse LD50 ml-1. Cowdria-infected goat blood was shown to retain infectivity when held on ice for up to 2 h, but when held at room temperature infectivity declined by greater than 50% in 2 h. The mouse assay detected Cowdria in feeding female Amblyomma variegatum only on the eighth day of feeding and in feeding males on the second and eleventh days of feeding. Cowdria was shown to persist in the hemolymph of the soft tick Ornithodoros coriaceus for a period of at least 2 years.
采用小鼠致死剂量测定法检测了反刍动物考德里氏体（Cowdria ruminantium）的一种小鼠致病菌株（夸尼扬加菌株），该菌株是山羊和蜱虫中“心水病”的病原体。山羊血液中立克次氏体生物的滴度与山羊的发热反应直接相关，发热消退后立克次氏体无法检测到。山羊血液中最大立克次氏体滴度为10³小鼠半数致死量/毫升。研究表明，感染考德里氏体的山羊血液在冰上保存长达2小时仍保持感染力，但在室温下保存2小时感染力下降超过50%。小鼠测定法仅在进食的第八天在雌性杂色斑蜱（Amblyomma variegatum）中检测到考德里氏体，在进食的雄性蜱虫中分别在进食的第二天和第十一天检测到考德里氏体。考德里氏体在软蜱科里亚斯钝缘蜱（Ornithodoros coriaceus）的血淋巴中至少持续存在2年。
