娱乐性用水中隐孢子虫的分子生态解析及其健康风险

Waterborne outbreaks of cryptosporidiosis have been reported throughout the world, especially in developed countries, making contamination of Cryptosporidium oocyst one of leading problems concerned by the environmental fields. In recent years, outbreak of recreational water-associated cryptosporidiosis was more frequent than that of drinking water-associated, so is the cases. That is to say, transmission through recreational water has became the main route of cryptosporidiosis. However, the concentration, species/genotype of Cryptosporidium in recreational water in China is still unclear. Moreover, this parasite is not listed as one of the test index of water quality standards. So, it is difficult to understand the risk of this parasite. In the present study, methods for the detection and genotyping of Cryptosporidium in different recreational waters will be developed. Occurrence and genotyping of Cryptosporidium in recreational water will be investigated and the contaminate source and infection of Cryptosporidium will be identified. On the other hand, studies will be conducted to estimate water ingestion during water recreation, so does the age-cohort distribution of the exposed consumer population. And then, comprehensive quantitative microbial risk assessment of Cryptosporidium infection, considering not only concentration but also genotyping and infection, will be performed based on the dose-response relation of Cryptosporidium. The above-mentioned research will help make environmental decisions to control waterborne cryptosporidiosis, which is of great significance to eliminate the potential danger to human health.

以水为传播媒介由隐孢子虫引发的疾病在全球范围内不断暴发流行，使其成为了国际上广为关注的热点环境问题之一。近年来，娱乐性用水途经导致隐孢子虫集体感染频次和感染人数均已超过饮用水途经，成了隐孢子虫介水性暴发感染的最主要传播途经。然而，娱乐性用水中隐孢子虫的浓度、种类/基因型等分布特征以及其健康风险问题仍是很不清楚，其水质标准也未将隐孢子虫列入检测项目。本研究将在建立适合不同类型娱乐性用水中隐孢子虫的检测与种类识别等方法基础上，系统研究我国代表性城市典型娱乐性用水中隐孢子虫的数量、种类和基因型的分布特征，识别其主要污染来源和感染性；对我国典型娱乐性用水的暴露人群的结构、摄入水量等进行评估。然后根据剂量-致病效应关系，综合考虑隐孢子虫的浓度、种类/基因型和感染性，构建健康风险的定量评估体系，阐明我国通过娱乐性用水感染隐孢子虫的健康风险，为卫生和供水部门针对隐孢子虫进行风险消减和管理提供科学依据。

娱乐性用水途径导致隐孢子虫和贾第虫（简称“两虫”）集体感染频次和感染人数均已超过饮用水途经，成了“两虫”介水性暴发感染的最主要传播途经。本项目建立了以碳酸钙浓缩－密度梯度分离纯化－免疫荧光分析为主要步骤的显微镜检测“两虫”的分析方法，以感染人结直肠癌HCT-8细胞-免疫荧光分析为主要步骤的隐孢子虫感染性鉴别方法和基于基因序列分析的“两虫”种类/基因型识别方法；调查了典型娱乐性用水中“两虫”的数量、种类和基因型的分布，以及暴露人群特征；构建了基于疾病负担（DALY）的“两虫”感染健康风险评估体系，初步阐明了我国娱乐性水体中“两虫”的健康风险。结果表明：（1）调查的人工游泳池水样中隐孢子虫阳性率为27.16％，浓度为0～4个/10L，贾第虫阳性率为23.24％，浓度为0～3个/10L；某水上娱乐公园湖水中隐孢子虫检出率为86％（55/64），浓度为0～15个/10L，贾第虫检出率为98％，浓度为0～43个/10L；调查的海滨浴场未检出“两虫”；（2）种类/基因型从游泳池检测到的“两虫”有人隐孢子虫、微小隐孢子虫、蓝氏贾第虫聚类A和B，均为人感染型，说明人是泳池“两虫”的主要来源；娱乐湖水中检测到微小隐孢子虫、安氏隐孢子虫、人隐孢子虫、火鸡隐孢子虫、C. fragil和cervine基因型，以及蓝氏贾第虫聚类A、B和D，其主要来源为动物和人；（3）因划船、涉水活动等有限接触娱乐性用水感染隐孢子虫的年概率为1.05×10^-4，贾第虫的为1.82×10^-3；因游泳等全身性接触导致的人均隐孢子虫病负担为3.60×10^-6 DALYs，贾第虫为5.37×10^-6 DALYs，两者合计为8.97×10^-6，约占与水相关的腹泻疾病负担（2.5×10^-3 DALYs）的0.36%。上述研究为水处理行业针对“两虫”建立有效地水质管理机制提供了科学技术基础，对于保障水体安全具有重大意义。上述研究为环境、卫生和供水等部门针对“两虫”进行风险消减和管理提供科学依据，对于防范隐孢子虫病或贾第虫病，提高人群生活质量等方面具有重大意义。