Komatsu Shintaro, Kimura Daisuke, Paller Vachel Gay V, Uga Shoji
Department of Parasitology, Faculty of Health Sciences, Kobe University Graduate School of Health Sciences, Japan.
Department of Molecular Microbiology and Immunology University of Nagasaki, Japan.
Trop Med Health. 2014 Mar;42(1):35-42. doi: 10.2149/tmh.2013-34. Epub 2014 Feb 18.
Centrocestus armatus is an intestinal parasite belonging to the family Heterophyidae. We developed an apparatus for recovering cercariae and clarified the infection dynamics of this parasite. To clarify the circadian rhythm of cercarial shedding in the summer season, we filtrated 30 l of river water every 2 h for 24 h. Cercariae were first detected between 06:00 and 08:00 h, increased over time to reach peak at 16:00 h and decreased thereafter, thus showing a single-peak pattern. In a survey of seasonal change, approximately 200 cercariae were contained in 1 l of river water during the summer season, while none were found during the winter. This cercarial shedding pattern appeared to be related to sunrise/sunset and water/atmosphere temperature. Therefore, we examined whether cercarial shedding was affected by light or temperature changes under laboratory conditions, and confirmed that both light and temperature were important factors for cercarial shedding. Light was a stronger factor than water temperature. Cercarial shedding of C. armatus occurred in response to temperature and light. The change in the number of juvenile metacercariae detected in fish brain corresponded with monthly detection rates of cercariae; however, the incidence of new infections decreased in August. This suggests that Nipponocypris temminkii contains a defense mechanism against new infections that may have hindered the increase in parasite infectivity. These results clarified the smooth infection from the first to the second intermediate host of C. armatus in the endemic river. Throughout the study period, fecal samples were collected from 19 kites, 114 herons, and three unidentified species. However, our results using C. armatus showed a low value of 1% in herons and 5% in kites. The infection dynamics of final host to first intermediate host need to be further investigated.
武装中带吸虫是一种属于异形科的肠道寄生虫。我们开发了一种用于收集尾蚴的装置，并阐明了这种寄生虫的感染动态。为了阐明夏季尾蚴逸出的昼夜节律，我们在24小时内每2小时过滤30升河水。尾蚴最早在06:00至08:00之间被检测到，随时间增加，在16:00达到峰值，此后下降，呈现单峰模式。在一项季节性变化调查中，夏季每升河水中约含有200个尾蚴，而冬季未发现尾蚴。这种尾蚴逸出模式似乎与日出/日落以及水/大气温度有关。因此，我们在实验室条件下研究了尾蚴逸出是否受光照或温度变化的影响，并证实光照和温度都是尾蚴逸出的重要因素。光照比水温的影响更强。武装中带吸虫的尾蚴逸出受温度和光照的影响。在鱼脑中检测到的稚后尾蚴数量变化与尾蚴的月度检测率相对应；然而，8月份新感染的发生率下降。这表明日本鲫含有一种针对新感染的防御机制，可能阻碍了寄生虫感染性的增加。这些结果阐明了在地方性河流中武装中带吸虫从第一中间宿主到第二中间宿主的顺利感染。在整个研究期间，从19只鸢、114只鹭和3个未鉴定物种中采集了粪便样本。然而，我们对武装中带吸虫的研究结果显示，鹭的感染率较低，为1%，鸢的感染率为5%。终末宿主到第一中间宿主的感染动态需要进一步研究。
