湖区日本血吸虫中间宿主钉螺大范围自然消亡的生态学研究

Oncomelania hupensis is the sole intermediate host of schistosome japonicum, and snail control is one of the most effective measures for the prevention and control of schistosomiasis. In some endemic areas of schistosomiasis, we find the lasting natural demise of snails in the large-scale snail habitats. Our preliminary studies indicated that the changes in water levels might not be a direct factor resulting in the natural demise of snails, however, we find that there is distribution of special microbes in the marshlands with natural demise of snails. Hence, we speculate that the natural demise of snails may be related to changes in ecology of the marshlands. Thus, based on our previous researches, a marshland with natural demise of snails, a marshland with snails and a marshland of their junction will be selected as the study fields. The environmental pollutants will be detected; microorganisms will be cultured and isolated; DNA of all environmental microorganisms will be sequenced by High-Throughput Sequencing; the environmental factors related to snails will be observed; and the free field simulation experiments for snails will be carried out. The differences of the environmental pollutants and their degree of pollution, microbial species and community structure, and environmental factors among these three marshlands will be comparatively analyzed to seek the ecological factors which may play key role in the natural demise of snails, and then, the laboratory simulation experiments will be implemented to validate these possible key factors and find the environmental microbial strains which can inhibit the breeding of snails. This study not only can deepen understanding of the ecological laws of snails, but also can provide a scientific basis for seeking a new snail control strategy based on ecological intervention.

钉螺是日本血吸虫唯一的中间宿主，控制钉螺是血吸虫病防治最有效的措施之一。我们调查发现在一些有螺洲滩发生了大范围、持久的钉螺自然消亡现象，初步研究预示水位变化可能不是钉螺消亡的直接原因，但发现钉螺消亡洲滩存在特殊的微生物分布。我们推测钉螺自然消亡现象可能与该类洲滩的生态变化有关。为此本研究拟在已有研究基础上，选择钉螺自然消亡洲滩、邻近有钉螺孳生洲滩以及二者的交界洲滩作为研究现场，检测现场污染物，培养分离现场微生物，采用高通量测序技术检测全部环境微生物的DNA，观测现场环境条件，进行现场钉螺投放模拟试验，对比分析不同洲滩在污染物种类及其污染程度、微生物种类及其群落结构、环境条件等方面的差异，并进行实验室模拟试验，探寻并验证在湖区洲滩钉螺自然消亡中可能起关键作用的因素以及具有抑制钉螺孳生的环境微生物菌株。本研究不仅能深化对钉螺生态规律的认识，还将为寻找基于生态干预的新型钉螺防制对策提供科学依据。

钉螺是日本血吸虫唯一的中间宿主，控制钉螺是血吸虫病防治最有效的措施之一。近年来湖区一些有螺洲滩发生了大范围、持久的钉螺自然消亡现象。探寻湖区洲滩钉螺自然消亡的原因，不仅能深化对钉螺生态规律的认识，还将为寻找基于生态干预的新型钉螺防制对策提供科学依据。本项目选择钉螺自然消亡洲滩、邻近有钉螺孳生洲滩以及二者的交界洲滩作为研究现场，检测现场污染物，培养分离现场微生物，采用高通量测序技术检测全部环境微生物的DNA，观测现场环境条件，进行现场钉螺投放模拟试验，对比分析不同洲滩在污染物种类及其污染程度、微生物种类及其群落结构、环境条件等方面的差异，并进行实验室模拟试验。探寻并验证在湖区洲滩钉螺自然消亡中可能起关键作用的因素以及具有抑制钉螺孳生的环境微生物菌株。重要结果为：1）土壤和水体污染物可能不是引起洲滩钉螺自然消亡的直接原因，无螺洲滩的pH不在钉螺的适宜范围之内，提示pH可能与钉螺的自然消亡有关；2）土壤和水体中细菌群落结构和真菌群落结构在有螺洲滩、交界洲滩和无螺洲滩之间存在明显差异；3）洲滩的高程、土壤含水量、水淹天数和温度等环境因素是影响钉螺分布的因素，但不是钉螺自然消亡的直接原因；4）土壤和水体的理化性质与真菌群落结构、细菌群落结构相关，它们可能通过影响微生物群落结构间接导致了钉螺的消亡；5）钉螺投放自然消亡洲滩水淹1个月，存活率仅30.17%，投放3个月后，实验钉螺全部死亡，说明钉螺自然消亡洲滩会影响钉螺的生存率；6）在有螺洲滩水淹并不会改变钉螺体内微生物的总数和多样性，而钉螺自然消亡洲滩会对钉螺体内的微生物总数和多样性造成显著影响；7）筛选到了14株具有杀钉螺效果的微生物菌株。我们的研究结果可以为生物灭螺方法的研究、生物灭螺剂的开发利用提供新的方向，更为重要的是可以为血吸虫病消除策略的制订开拓新的思路。