Department of Veterinary Biosciences, The Ohio State University, Columbus, OH 43210, USA.
Environ Microbiol. 2008 Aug;10(8):2064-73. doi: 10.1111/j.1462-2920.2008.01625.x. Epub 2008 Apr 15.
Neorickettsia risticii, the obligatory intracellular bacterium that causes Potomac horse fever, has been detected in various developmental stages of digenetic trematodes in the environment. Neorickettsia risticii-infected gravid trematodes were identified as Acanthatrium oregonense, based on morphologic keys. However, whether immature trematodes harbouring N. risticii are also A. oregonense was unknown. The objective of this study was to infer the life cycle of N. risticii-positive trematode hosts and transstadial transmission of the bacterium by molecularly characterizing the relationship among adult and immature stages of trematodes confirmed infected with N. risticii. Sequences of 18S ribosomal RNA genes up to 1922 bp in size were obtained from infected adult gravid trematodes, sporocysts and cercariae, and metacercariae. The sequences from the different immature stages of trematode are closely related to those of adult trematodes, some with 100% sequence identity; thus, they likely are life stages of A. oregonense. Comparisons with known 18S ribosomal RNA gene sequences of other digenetic trematodes indicated that all tested stages of the N. risticii-positive trematodes belong to the family Lecithodendriidae, supporting the morphological identification.
赖氏尼亚虫是一种专性细胞内细菌，可引起波托马克马热，已在环境中的各种双殖吸虫发育阶段中检测到。根据形态学关键特征，感染赖氏尼亚虫的怀孕吸虫被鉴定为俄勒冈棘口吸虫。然而，是否携带赖氏尼亚虫的未成熟吸虫也是俄勒冈棘口吸虫尚不清楚。本研究的目的是通过分子特征鉴定确认感染赖氏尼亚虫的成虫和未成熟阶段之间的关系，推断赖氏尼亚虫阳性吸虫宿主的生命周期和细菌的跨期传播。从感染的成年怀孕吸虫、孢囊和尾蚴以及囊蚴中获得了长达 1922 个碱基对的 18S 核糖体 RNA 基因序列。从不同未成熟阶段的吸虫中获得的序列与成年吸虫的序列密切相关，有些具有 100%的序列同一性；因此，它们可能是俄勒冈棘口吸虫的生活阶段。与已知的其他双殖吸虫的 18S 核糖体 RNA 基因序列进行比较表明，所有测试的赖氏尼亚虫阳性吸虫阶段均属于片形科，这支持了形态学鉴定。
