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

• 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
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-19406010/
• 关键词: ビルハルツ住血吸虫; ケニア; 対策法; 囮貝; ミラシジウム; 侵入; 走化性運動; 囮; 貝; 住血吸虫; 中間宿主; 分泌物; 誘引力; 季節性; 感染阻止

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

诱螺可作为发展中国家控制血吸虫病的一种新手段。本研究试图在肯尼亚夸莱血吸虫病流行区的主要非易感螺种中寻找诱饵螺候选者。我们研究了1）由蜗牛排泄物和分泌物产生的毛蚴趋化性（蜗牛调节水：SCW），2）毛蚴在蜗牛中的渗透，3）在实验室中评估非敏感蜗牛的诱饵效果，以及4）在传播地点的诱饵蜗牛候选人的现场应用。所用螺种为敏感螺种球泡螺（Bulinus globosus）和非敏感螺种锈色艳后螺（Cleopatra ferrugulosa）、单色环棱螺（Bellamya unicolor）、卵兰尼斯特螺（Lanistes ovum）、类黑螺（Melanoides sp.），毛蚴来源于夸莱小学生的虫卵。来自B.globosus的SCW引起最高的毛蚴反应。毛蚴对来自L.ovum的SCW的反应与这些基因相似 ...更多信息 由B.globosus。毛蚴表现出轻微的阳性趋化性SCW从C.ferruginea。其他两种动物没有引起反应。2)蜗牛中的毛蚴渗透。PCR证实毛蚴在B中渗透。globosus，但没有显示毛蚴在其他蜗牛的存在。3)实验室内候选钉螺诱集效果评估。我们试图发现当易感和非易感蜗牛都占据同一空间时，插入非易感蜗牛是否可以保护易感蜗牛免受感染。在其他实验中，将不敏感的蜗牛放置在通道的中心。然后在一端放置球形B杆菌，在另一端引入毛蚴。在任何实验中，我们都没有发现插入非易感蜗牛保护球型芽孢杆菌。4)诱螺候选物在传播点的现场应用。在3个调查点进行了1年的钉螺调查，结果表明，通过大量引进锈色金纹螺，使非易感性锈色金纹螺的种群密度提高到原来的3倍。从其他繁殖地收集的铁藻。随后又进行了一年的钉螺跟踪调查。结果表明，在所有站点的B.globosus的感染率略有下降，但没有统计学意义。讨论：本研究表明，在我们的研究领域的一些螺繁殖引起miracidial反应。然而，目前的研究表明，在自然环境中的感染频率可能不会受到非敏感蜗牛的存在和密度的影响。少