我国重要蚊虫感染和传播西方马脑炎病毒的实验研究

发布时间：2018-05-26 17:37

  本文选题：西方马脑炎病毒 + 淡色库蚊　； 参考：《中国人民解放军军事医学科学院》2007年博士论文

【摘要】： 西方马脑炎病毒(western equine encephalomyelitis virus，WEEV)属于披膜病毒科(Togaviridae)甲病毒属(Alphaviruses)。它能够引起人类和马等动物的致死性疾病——脑炎，对马的病死率可达50％，对人的病死率最高可达10％，婴幼儿患者常会导致智力低下、行为失常等。目前已知该病主要分布于加拿大、美国西部和中部、墨西哥、圭亚那、巴西、阿根廷、秘鲁、智利和乌拉圭等国家。该病在北美地区呈地方性流行，以不规则的间隔在马和人群中引起流行。环跗库蚊(Culex tarsalis)已被证明是北美地区西方马脑炎病毒的主要传播媒介，同时血清学调查证明了鸟类在病毒循环中的作用。在自然界中，病毒只在野鸟—蚊之间进行传播，主要是在环跗库蚊与野鸟之间；人和马是其非固有的感染对象，称为“终末宿主”。此外，经证实能够自然或实验室感染WEEV的还有其它库蚊属(Culex)、按蚊属(Anopheles)、伊蚊属(Aedes)等7个属20多种蚊虫，也有从虱、蜱、螨等节肢动物体内分离病毒的报道。虽然西方马脑炎只在美洲大陆上发生，但其仍然是国际严密监控的人畜共患传染病。除了美洲以外，波兰和前苏联也曾报道从正常人血中测得西方马脑炎抗体，1962年首次从俄罗斯分离出西方马脑炎病毒株Y62-33。我国1990年分别从新疆乌苏县的一组赫坎按蚊(Anopheles hyrcanus)和博乐县的全沟硬蜱(Ixodes persulcatus)中分离出WEEV，这是在欧亚大陆除俄罗斯外发现的第二例WEEV分离的报道。在对我国人体血清学调查中发现，WEEV抗体阳性率为2.71％。这些情况都表明了WEEV在我国的存在。近年来我国每年均有大量不明原因发热及脑炎病例的报道，提示WEEV可能是我国感染性疾病的新病原之一。此外，WEEV被列为二类生物恐怖试剂，如果WEEV经气溶胶方式撒布后，当地的宿主动物如鸟类等被感染，那么易感蚊虫就有可能通过吸血将西方马脑炎传播给人类，造成更大范围的传染病暴发。因此针对WEEV对我国潜在的威胁，我们首先需要明确在我国的一些优势种蚊虫能否感染和传播WEEV，了解它们对WEEV的传播能力，结合生态习性确定哪些是主要的潜在媒介，以便制订应对一旦西方马脑炎暴发后的相应的防治策略。 在我国，淡色库蚊(Cx.p.pallens)和致倦库蚊(Cx.p.quinquefasciatus)是尖音库蚊复合组(Cx.pipiens Complex)成员，嗜吸人血，兼吸禽血，是我国城镇的优势蚊种；白纹伊蚊(Ae.albopictus)和埃及伊蚊(Ae.aegypti)是登革热的主要传播媒介，也是我国的重要蚊种；三带喙库蚊(Cx.tritaeniorhynchus)广泛地分布于我国水稻种植区，嗜吸畜血，兼吸人、鸡血等。本研究以这几种在我国十分重要的蚊种为对象，在实验室条件下，通过蚊虫叮咬人工感染WEEV的来亨鸡，采用免疫荧光检测病毒抗原和RT-PCR检测病毒核酸等方法检测蚊虫体内病毒，确定受试蚊虫对WEEV的易感性和传播能力；探讨蚊虫对WEEV的易感机制，为进一步深入理解病毒与媒介的相互作用，寻求对病媒蚊虫的有效防控手段提供科学依据。本工作主要结果如下： 1．我国重要蚊种对WEEV的经口感染率 在实验室条件下，叮咬人工感染WEEV的来亨鸡后，淡色库蚊、致倦库蚊、三带喙库蚊、白纹伊蚊和埃及伊蚊对WEEV均易感，其感染率分别为45.5％、60.0％、80.0％、36.7％和25.0％，不同蚊种之间的感染率有显著性差异(x~2=13.709，P=0.008)，其中三带喙库蚊感染率最高，为80.0％。 2．我国重要蚊种对WEEV的刺叮传播率 在实验室条件下，淡色库蚊、致倦库蚊、白纹伊蚊和埃及伊蚊都能通过刺叮吸血将体内的WEEV传播给易感动物1～3日龄的来亨鸡，传播率分别为40.74％、53.13％、57.14％和45.16％，不同蚊种之间的传播率没有显著性差异(x~2=1.879，P=0.598)。 3．WEEV在蚊虫体内的散布率 在实验室条件下，WEEV在已感染的淡色库蚊、致倦库蚊、三带喙库蚊、白纹伊蚊和埃及伊蚊体内均能扩散至足，散布率分别为60.0％、61.1％、75.0％、54.5％和50.0％。不同蚊种间的散布率没有显著性差异(x~2=1.229，P=0.873)。 4．WEEV在感染蚊虫体内扩散与蚊虫经口传播病毒的相关性研究 本研究通过对感染和传播实验中的单只蚊虫进行标记，根据它们感染、扩散和传播的结果进行统计分析发现，感染病毒并扩散至足的绝大多数蚊虫能够将病毒传播给易感动物、也有极少数不能经口传播；一些感染病毒但未扩散至足的蚊虫也是一部分能够经口传播而另一部分不能；还存在一些体内检测不出病毒，，其叮咬的来亨鸡却能被感染。 5．西方马脑炎病毒抗原在经口感染淡色库蚊体内的分布 淡色库蚊在经口感染WEEV 3～4天后，部分蚊虫中肠壁见有WEEV的侵染。个别蚊虫后肠出现阳性斑块；第7～10d，部分蚊虫中肠、马氏管、卵巢、后肠均见病毒侵染；第10～14d，除中肠和卵巢等呈阳性反应外；可见唾液腺亦被病毒侵染；但有些蚊虫个体仅在中肠有阳性反应，其它组织器官均为阴性；还有部分蚊虫个体组织器官均未见阳性反应。因此认为，淡色库蚊对WEEV的易感性存在个体差异，不易感的个体体内可能存在中肠屏障，而传播能力的差异可能是由于唾液腺屏障的存在。
[Abstract]:The western equine encephalitis virus ( WEEV ) belongs to the genus Togaviridae . It can cause fatal disease _ encephalitis in humans and horses . The mortality rate of horses is up to 10 % . The disease is endemic in North America . The disease is endemic in the West and Central America , Mexico , Guyana , Brazil , Argentina , Peru , Chile and Uruguay .
In the past few years , China has reported that WEEV may be one of the new pathogens of infectious diseases in China . In recent years , China has reported that WEEV is one of the new pathogens of infectious diseases in China . In recent years , China has reported that WEEV is a new pathogen of infectious diseases in China .









In our country , Cx . p . quinquefasciatus and Cx . p . quinquefasciatus were the members of Cx . pileus complex .
aegypti and aegypti are the main media of dengue fever , and it is also an important mosquito species in China ;
In order to determine the susceptibility and transmission ability of the infected mosquitoes to WEEV in the laboratory , the infected chickens infected with WEEV were detected by immunofluorescence assay and RT - PCR , and the susceptibility and transmission ability of the infected mosquitoes to WEEV were determined .
To explore the susceptibility mechanism of mosquitoes to WEEV , to further understand the interaction between virus and medium , to provide scientific basis for effective prevention and control of vector mosquitoes . The main results of this work are as follows :









1 . Infection rate of China ' s important mosquito species to WEEV









The infection rate was 44.5 % , 60.0 % , 80.0 % , 33.7 % and 25.0 % , respectively , and the infection rate among different species was significantly different ( x ~ 2 = 13.709 , P = 0.008 ) . Among them , the infection rate among the three species was the highest , which was 80.0 % .









2 . sting propagation rate of important mosquito species in China to WEEV









The WEEV in the body could be transmitted to the 1 - 3 day - old hen in the laboratory . The rate of transmission was 40.74 % , 53.13 % , 57.14 % and 45.16 % , respectively , and there was no significant difference between the different species ( x ~ 2 = 1.879 , P = 0.598 ) .









3 . Distribution rate of WEEV in mosquitoes









In laboratory conditions , WEEV was able to diffuse to the foot in the infected light - colored culex , quinquefasciatus , tritaeniorpius , aegypti , aegypti and aegypti , with the spreading rate of 60.0 % , 61.1 % , 75.0 % , 54.5 % and 50.0 % , respectively . There was no significant difference among the spreading rates among different species ( x ~ 2 = 1.229 , P = 0.873 ) .









Study on the relationship between the diffusion of WEEV and the spread of mosquitoes in infected mosquitoes









Based on the results of infection , diffusion and transmission , the study found that the majority of mosquitoes infected with the virus and spread to the foot were able to spread the virus to the susceptible animals , and that a small number of mosquitoes could not be transmitted through the mouth .
Some mosquitoes that are infected with the virus but not enough to spread to the foot are also part of the virus that can travel through the mouth and the other part cannot ;
There are also some in - vivo detection of the virus , but the bite of the hen can be infected .









5 . Distribution of the Western equine encephalitis virus antigen in the body of the infected pale - color culex piquefasciatus









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