Novel strategy for control of schistosomiasis : Decoy snails that can reduce the number of miracidia reaching the intermediate snails

控制血吸虫病的新策略：诱饵蜗牛，可减少到达中间蜗牛的毛蚴数量

基本信息

批准号：
19406010
负责人：
AOKI Yoshiki
金额：
$ 10.73万
依托单位：
Nagasaki University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2007
资助国家：
日本
起止时间：
2007 至 2009
项目状态：
已结题

项目摘要

Decoy snails could be used as a new tool for the control of schistosomiasis in the developing countries. The present study was attempted to find the decoy snail candidate in main species of non-susceptible snails at the endemic area of schistosomiasis hematobia, in Kwale, Kenya. We studied 1) miracidial chemotaxis generated by excretion and secretion from snails (snail-conditioned water : SCW), 2) miracidial penetration in snails, 3) assessment of decoy effect in non-susceptible snails in laboratory, and 4) field application of the decoy snail candidate at the transmission sites. The snails used were susceptible snail Bulinus globosus and non-susceptible snails Cleopatra ferruginea, Bellamya unicolor, Lanistes ovum, Melanoides sp. The miracidia used were from the eggs obtained from the school children in Kwale.Results : 1) Miracidial chemotaxis generated by SCW. SCW from B.globosus elicited the highest miracidial response. The response of miracidia to SCW from L.ovum mimicked those gen … More erated by B.globosus. Miracidia showed slight positive chemotaxis to SCW from C.ferruginea. Other two species did not elicit the response. 2) Miracidial penetration in snails. PCR confirmed miracidial penetration in B. globosus, but did not show the presence of miracidia in other snails. 3) Assessment of decoy effect in candidate snails in laboratory. We attempted to find whether interposed non-susceptible snails could protect the susceptible snails from infection when susceptible and non-susceptible snails both occupied the same space. In other experiment, non-susceptible snails were placed at the center of the channels. Then B.globosus was placed at one end and miracidia were introduced at the other end. In any experiments, we failed to find that interposed non-susceptible snails protected B.globosus. 4) Field application of decoy snail candidate at the transmission sites. After one year snail survey at 3 study sites, the population of non-susceptible snail, C.ferruginea, was raised to the density 3 times bigger than the original by introduction of huge number of C. ferruginea collected from other breeding sites. Then the follow-up snail survey was conducted for one year more. The results showed a slight reduction in the infection rate of B.globosus at all sites, but there was no statistical significance.Discussion : The present study showed that some snails breeding in our study area elicited miracidial response. However, the present study suggests that frequency of infection in a natural environment might not be influenced by the presence and density of non-susceptible snails. Less

诱饵蜗牛可以用作控制发展中国家控制血吸虫病的新工具。本研究试图在肯尼亚克瓦尔的血吸虫病血吸虫病的内在蜗牛区域中找到诱饵蜗牛候选者。我们研究了1）由蜗牛的极端和分泌产生的奇迹趋化性（蜗牛条件水：SCW），2）蜗牛中的奇迹渗透，3）3）评估实验室中非启发性蜗牛中诱饵效应的评估，以及4）4）在变速器上诱导蜗牛候选者的现场应用。所使用的蜗牛是易感蜗牛Bulinus Globosus和不可启发性的蜗牛，Cleopatra Ferruginea，Bellamya Unicolor，Lanistes ovum，Melanoides sp。使用的奇迹是从Kwale中的小学生那里获得的卵。1）SCW产生的奇迹趋化性。 B.lobosus的SCW引起了最高的奇迹反应。 Miracidia对L.Ovum的SCW的反应模仿了那些Gen……更受B. globosus的反应。奇迹症对ferruginea的SCW表现出略微阳性的趋化性。其他两个物种没有引起反应。 2）蜗牛中的奇迹渗透。 PCR证实了球芽孢杆菌中的奇迹渗透，但没有在其他蜗牛中显示出奇迹。 3）评估实验室候选蜗牛的诱饵效应。我们试图发现，当易感性和不启发性蜗牛都占据相同的空间时，插入的不启发性蜗牛是否可以保护易感蜗牛免受感染。在其他实验中，将不启发性的蜗牛放在通道的中心。然后将b.globosus放在一端，并在另一端引入奇迹。在任何实验中，我们都没有发现插入的非启发性蜗牛受保护的b.lobosus。 4）在传输站点将诱饵蜗牛候选者的现场应用。在3个研究地点进行了一年的蜗牛调查后，通过从其他育种地点收集的大量ferruginea，将非启发性蜗牛C. ferruginea的种群抬高到密度的3倍。然后，进行了一年的后续蜗牛调查。结果表明，在所有部位，b.lobosus的感染率略有下降，但没有统计学意义。结论性：本研究表明，我们的研究区域中的一些蜗牛繁殖引起了奇迹反应。但是，本研究表明，自然环境中感染的频率可能不会受到不敏感蜗牛的存在和密度的影响。