上海城市环境尖音库蚊复合组种群共生状态及嗜血习性研究

The Culex pipiens complex (Diptera: Culicidae) includes four subspecies as Cx. p. pallens, Cx. p. quinquefasciatus, Cx. p. molestus and Cx. p. pipiens. This mosquito complex plays a major role in the transmission of West Nile virus (WNV) worldwide, but different vector capabilities are found among the subspecies in WNV transmissions due to their different host preference. As birds are the main reservoir hosts and mammals (including human beings) are the end hosts of WNV, WNV epidemics are mainly caused by mosquitoes which can both bite birds and mammals (including human beings).. Being different from other areas of China, where only 1 or 2 subspecies can be found, there are all of the four subspecies coexisting in Shanghai, and symbiosis and heterozygosity among different subspecies contribute to substantially morphological and genetic polymorphisms in this region. However, the detailed polymorphism and population composition of the mosquito complex have not been well studied in Shanghai. Moreover, it has been found that small mammals like cats and dogs in Shanghai were tested seropositive of WNV antibodies. Therefore, it is urgent to study the host preference behaviors of the symbiotic subspecies.. In this study, comprehensive mosquito sampling would be conducted from multiple temporal and spatial dimensions, and the symbiotic status and polymorphism of the culex pipiens complex are clarified from the perspective of micro-morphology and molecular biology. Moreover, experiments are designed to detect each subspecies’ behaviors of host preference to birds and mammals (including humans), so as to provide quantitative evidence for risk analysis of WNV transmissions in Shanghai.

尖音库蚊复合组包含4个亚种：淡色库蚊、致倦库蚊、骚扰库蚊和尖音库蚊。该复合组蚊虫是全球范围内西尼罗病毒（WNV）的最主要传播媒介，不同亚种间因嗜血习性差异可表现出不同的媒介能力。WNV病毒储存宿主是鸟类、终宿主是哺乳动物，因此传播该病毒的蚊媒需同时兼备吸鸟类及哺乳动物（包括人）血液的能力。.尖音库蚊复合组在国内大部地区以1~2个亚种单一分布，上海是目前国内唯一发现4个亚种共生的地区，且不同亚种间因共生和杂合表现出形态及基因的多态性，针对该多态性的种群构成目前仍鲜有研究涉及。已有研究发现上海地区的猫、狗等小型动物WNV病毒抗体阳性，因此亟需针对共生的各亚种种群进行嗜血习性研究。.本研究拟从多个时间、空间维度对上海城市环境蚊虫进行采样，从微形态、分子生物角度阐明该复合组种群的共生状态及多态性；设计实验检测各亚种对鸟类和哺乳动物（包括人）的嗜血选择性，为上海地区面临的WNV病毒风险提供定量依据。

项目背景：尖音库蚊复合组是全球性分布的媒介蚊虫复合组，包含淡色库蚊、致倦库蚊、骚扰库蚊和尖音库蚊4个亚种。该复合组蚊虫是全球范围内西尼罗病毒（WNV）的主要传播媒介，当具备对鸟类和人类（哺乳动物）兼吸血性时可以有效传播WNV病毒。目前已知上海地区是国内少有的几个亚种共存的区域，但上海乃至国内该复合组各亚种的吸血习性尚缺乏研究。.研究内容：针对上海城市地面和地下等多种生境开展全面采样，形态学与分子生物学相结合，对各亚种共生状态、杂合情况及多态性进行解析；对不同种群进行饲养纯化，设计试验对各亚种的嗜血习性进行验证。.研究进展和重要结果：a). 多维度采集孳生阳性水样225个，尖音库蚊复合组蚊虫样本15433只，证实上海地区4个亚种共存，且存在杂合种；b). 地面排水系统，4个亚种共存，构成比例为致倦库蚊58.8% ＞骚扰库蚊19.9% ＞淡色库蚊7.67% ＞尖音库蚊2.8%，存在不同亚种的杂合种；c). 地下环境中，3个亚种共存，构成比例为骚扰库蚊41.92% ＞致倦库蚊33.31% ＞淡色库蚊14.54% ＞杂合种10.23%；d). 形态学研究证实，即使相同来源的杂合种群，尾器微形态亦表现出明显多态性；e). 设计多种蚊虫叮咬试验，包括单一宿主吸血试验和多宿主吸血选择性试验，纳入宿主包括人类志愿者，家鸡，家鸽，小白鼠和家兔。f). 骚扰库蚊对不同宿主的吸血率，人64.72% ＞鸡19.66% ＞鸽1.89% ＞鼠0/兔0；96次嗜血选择性证实，鸡＞鼠＞鸽＞兔；g).致倦库蚊、淡色库蚊和杂合种，亦嗜吸人血，鸟类叮咬率高于小型哺乳动物；但对不同鸟类的选择性，与骚扰库蚊存在差异；h).白纹伊蚊对小型哺乳动物的选择性显著高于鸟类（24.00% vs.8.44%）.主要结论：上海地区尖音库蚊复合组4个亚种共存；不同环境和季节，各亚种的构成比例存在明显差异；各亚种间杂合现象明显，尾器形态表现出明显多态性；不同于以往报道，证实骚扰库蚊的分布不止局限于地下环境，地面开放环境亦有广泛分布；尖音库蚊复合组各亚种均嗜吸人血，且对鸟类有明显的嗜血选择性和叮咬比；兼吸血性的现象代表着西尼罗病毒的媒介风险。