云南省洱源县乙型脑炎流行病学监测

本文作者于１９８６年５月－１９８８年２月对云南省乙脑高发行区洱源县右所镇的蚊类种群组成，季节消长，成蚊自然毒率；媒蚊密度与乙脑流行关系，猪群感染乙脑动态与人群发病的关系；乙脑流行前后人群免疫水平；乙脑病毒的分离与鉴定等项目进行了系统监测研究。结果表明：中华按蚊，纹库蚊是该地区优势蚊种，１－１１月可见蚊虫活动。从人房及畜厩捕获的中华按蚊，三带喙库蚊及麻翅库蚊中分离到乙脑病毒８株。证明中华按蚊及三带喙     

中国云南湄公河上游乙型脑炎传播媒介生物学及行为的研究

目的 探讨乙型脑炎病毒媒介在人房的季节消长、嗜血习性和叮人行为，以及其幼虫相关的生物学习性，从而制定出有效的媒介控制措施。方法 2001年6～12月，在云南南部湄公河上游，选取一个种植场，采用CDC诱蚊灯和人工诱捕的方法捕蚊；蚊胃血源环状沉淀法鉴定其嗜血习性以及孳生地调查幼虫孳生习性。结果 共捕获乙脑病毒媒介蚊虫5属、11种、5726只。无论是诱蚊灯还是人工诱蚊法，三带喙库蚊、伪杂鳞库蚊、棕头库蚊和中华按蚊的季节密度高峰都出现于6～8月的雨季；3种库蚊在村内和村外有整夜叮咬活动，但中华按蚊的叮人高峰出现在21：00之前。人房室内诱蚊灯捕蚊与室外人诱观察发现，室内捕捉乙脑病媒数量远高于室外。蚊胃血检测结果发现它们的人血指数都比较高；幼虫具有明显的特征性分布。结论 湄公河上游地区人房优势蚊种三带喙库蚊、伪杂鳞库蚊、棕头库蚊和中华按蚊的生物学及行为与以往畜圈调查的结果存在着差异。     

云南省德宏州蚊虫分布特点及乙型脑炎病毒分离

１９８３年５月以及１９８４年和１９８９年７￣８月，在云南省德宠州路西，瑞丽和盈江三县，市捕获成年雌性蚊虫９属４４种１９０８３只。三带喙库蚊，霜背库蚊，棕头库蚊和中华按蚊是农村畜圈的主要蚊种。伪白纹伊蚊和白纹伊蚊是野外竹林区的优势蚊种。对所获蚊虫用Ｃ６／３６细胞和乳鼠方法分离病毒，结果从三带喙库蚊中分离到乙型脑炎病毒２株，从霜背库蚊，白纹伊蚊和窄翅伊蚊中各分离出１株乙型脑炎病毒。分析认为，三带喙库蚊     

云南省乙型脑炎几个重要流行区的传播媒介调查

目的了解云南省乙型脑炎重要流行区传播媒介种群密度和地区分布。方法现场CDC诱蚊灯诱捕成蚊;吸蚊管人工捕蚊2种方法调查。结果CDC诱蚊灯诱捕成蚊法调查了5个县,捕获蚊虫6属37种8023只,其中思茅6属34种6786只,三带喙库蚊占49.01%;麻栗坡、马关、砚山、邱北、捕获蚊虫6属21种1237只,其中三带喙库蚊占71.06%;人工捕成蚊法调查了7个地区,捕获蚊虫5属21种11301只,其中思茅翠云区调查4个乡(镇)捕获蚊虫5属21种10482只,三带喙库蚊占64.44%,其它6个地区捕获蚊虫4属16种819只,乙型脑炎主要传播媒介三带喙库蚊景谷占49.13%,孟连占46.15%,陇川占35.59%;结论调查结果显示:这些地区乙型脑炎疾病传播媒介品种较多,特别是三带喙库蚊在乙型脑炎流行区种群大密度较高,地区分布较广,大量危险因素存在。     

中国云南湄公河上游乙型脑炎传播媒介生物学及行为的研究

目的　探讨乙型脑炎病毒媒介在人房的季节消长、嗜血习性和叮人行为,以及其幼虫相关的生物学习性, 从而制定出有效的媒介控制措施。　方法　2001 年 6~12 月,在云南南部湄公河上游,选取一个种植场,采用 CDC 诱蚊灯和人工诱捕的方法捕蚊;蚊胃血源环状沉淀法鉴定其嗜血习性以及孳生地调查幼虫孳生习性。　结果　共捕获乙脑病毒媒介蚊虫5属、11种、5 726只。无论是诱蚊灯还是人工诱蚊法,三带喙库蚊、伪杂鳞库蚊、棕头库蚊和中华按蚊的季节密度高峰都出现于 6~8 月的雨季;3 种库蚊在村内和村外有整夜叮咬活动,但中华按蚊的叮人高峰出现在 21:00 之前。人房室内诱蚊灯捕蚊与室外人诱观察发现,室内捕捉乙脑病媒数量远高于室外。蚊胃血检测结果发现它们的人血指数都比较高;幼虫具有明显的特征性分布。　结论　湄公河上游地区人房优势蚊种三带喙库蚊、伪杂鳞库蚊、棕头库蚊和中华按蚊的生物学及行为与以往畜圈调查的结果存在着差异。     

云南省通海县蚊虫2株乙型脑炎病毒的分离鉴定北大核心CSCD

目的了解云南省通海县蚊虫携带的乙型脑炎病毒(JEV)情况、分子特征及基因分型。方法2015年7月在云南省玉溪市通海县采用诱蚊灯在调查点通宵捕捉蚊虫,蚊虫研磨后分别接种BHK-21和C6/36细胞进行病毒分离,使用黄病毒属特异引物进行初步鉴定,使用乙型脑炎病毒E基因特异引物进行RT-PCR扩增及测序,使用Megalign、Genedoc、Mega7等软件进行序列分析。结果共捕获三带喙库蚊、中华按蚊、致倦库蚊和骚扰阿蚊2300只,其中三带喙库蚊为优势蚊种(78%)。分46批进行病毒分离,获得2株阳性分离物,接种BHK-21细胞96h,引起细胞病变。使用黄病毒属特异引物和乙型脑炎病毒E基因特异引物扩增均为阳性。序列分析结果显示,2株新分离乙型脑炎病毒与疫苗株SA14-14-2在E基因存在12个氨基酸差异位点,在8个与乙脑病毒毒力相关的位点上存在6个差异位点。E基因遗传进化分析显示,2株新分离病毒与基因Ⅰ型乙型脑炎病毒位于同一进化分支,核苷酸和氨基酸同源性分别为91.8%~99.1%和98.0%~100%。遗传进化分析显示,其与云南2016年蚊虫中分离的乙脑病毒株JEV/mosq/YN/2016亲缘关系较近,核苷酸和氨基酸同源性分别为99.1%和99.8%。结论云南省通海县分离的2株病毒鉴定为基因Ⅰ型乙型脑炎病毒,其与云南省近年来流行的毒株遗传进化关系较近。2毒株的E基因上与毒力相关的关键位点中有2个位点发生突变,结构域Ⅲ的关键抗原未发生改变,因此SA14-14-2减毒疫苗株仍可用于该地区人群的免疫接种,以预防乙型脑炎的发生和流行。     

云南省洱源县乙型脑炎媒蚊监测

本文作者对乙脑传播媒介进行了监测,结果表明,中华按蚊、纹腿库蚊是本地区的优势蚊种。从中华按蚊、纹腿库蚊、麻翅库蚊和三带喙库蚊体内分离到8株乙脑病毒。中华按蚊和三带喙库蚊与乙脑关系密切。9—10月份为乙脑发病高峰期。从麻翅库蚊中分离到乙脑病毒尚属国内首次报道,该蚊种在乙脑传播中的流行病学地位应引起重视。     

中国云浮口岸蚊媒病毒的首次调查

目的 掌握云浮国境口岸蚊类携带重要蚊媒病毒的现状,探讨提高口岸蚊媒病毒检测有效性的方法,为预防和控制口岸蚊媒传染病的发生提供科学依据。方法 于2011年5月~11月在云浮口岸捕捉活蚊,对蚊标本研磨液提取核酸后应用多重实时荧光RT-PCR技术快速筛查蚊类携带的登革热病毒、日本脑炎(乙脑)病毒、基孔肯雅病毒、西尼罗热病毒和黄热病毒。对实时荧光RT-PCR检测核酸阳性的标本进行PCR扩增和序列分析。结果 在云浮共采集39 254只蚊虫,鉴定后分为460组。经实时荧光RT-PCR检测,14组蚊虫乙脑病毒核酸阳性,其余病毒(登革热病毒、乙脑病毒、基孔肯雅病毒、西尼罗热病毒和黄热病毒)均为阴性。PCR扩增和序列分析显示云浮乙脑病毒属于基因Ⅰ型。所捕获的三带喙库蚊的最小感染率为0.937‰比中华按蚊的0.385‰稍高。结论 本研究首次在云浮口岸进行大规模系统的蚊媒病毒调查,云浮口岸的蚊虫很可能没有携带登革热病毒、基孔肯雅病毒、西尼罗热病毒和黄热病毒,但有少数蚊虫携带乙脑病毒。此次调查检出的基因Ⅰ型乙脑病毒是广东省内的首次报道,为今后蚊媒病毒的媒介监测检测工作提供了有效方法。虽然蚊虫最小感染率的差别没有统计学意义,但是蚊媒病毒病的暴发和流行风险仍然存在。     

云南楚雄2014年蚊媒及其病毒感染调查

目的了解云南楚雄元谋、武定和双柏3县蚊虫及其主要虫媒病毒种类,为制定出有效的虫媒传染病防控对策提供依据。方法2014年6-7月采用诱蚊灯在调查点通宵捕捉蚊虫,对现场采集蚊虫进行形态分类鉴定;采用C6/36细胞培养法和RT-PCR扩增目的基因片段对蚊虫体内病毒进行分离、鉴定。结果共捕获4属15种12 384只蚊虫,三带喙库蚊、中华按蚊、致倦库蚊和微小按蚊分别占捕获蚊虫总数的59.95%、19.31%、10.90%和 4.13%;C6/36细胞培养处理116组蚊虫,其中29组发生细胞病变,经基因鉴定为版纳病毒(BAV)、Totivirus 病毒(TOV)、乙型脑炎病毒(JEV)和Nam Dinh病毒(NDiV)4种,其中,三带喙库蚊的JEV、BAV、TOV和NDiV基因扩增批阳性率分别为1.87%、11.32%、3.77%和9.43%;希氏库蚊的NDiV基因扩增批阳性率为25.00%;致倦库蚊和中华按蚊的BAV、NDiV批阳性率分别为20.00%、33.34% 和5.00%、7.50%。结论楚雄地区蚊虫种类多,且以三带喙库蚊和中华按蚊为优势蚊种,从两种蚊虫标本中能分离到JEV、TOV、BAV和NDiV病毒,表明调查地区发生乙脑及其它虫媒病毒性疾病流行的危险较大。     

老挝波乔会晒县和敦蓬县居民区蚊虫种类调查

目的调查老挝波乔省会晒县和敦蓬县居民区成蚊种类组成,为制定当地媒介控制措施提供依据。方法采用诱蚊灯通宵捕蚊法和电动捕蚊器法采集成蚊,采用形态学方法鉴定蚊虫种类。结果共捕获蚊虫3亚科7属38种13 537只,乙型脑炎媒介三带喙库蚊和棕头库蚊属于当地优势蚊种,分别占捕获总数的75.57%(10 230/13 537)和13.61%(1 843/13 537);疟疾媒介中华按蚊和登革热媒介白纹伊蚊分别占捕获总数的0.57%(77/13 537)和0.94%(127/13 537)。结论老挝波乔省会晒县和敦蓬县蚊虫种类丰富,乙型脑炎媒介三带喙库蚊、疟疾媒介中华按蚊和登革热媒介白纹伊蚊广泛存在,提示当地存在乙型脑炎、登革热、疟疾等重要虫媒传染病流行的风险,当地应加强对上述媒介蚊虫的监测。     

Short report: the first isolation of Japanese encephalitis virus from mosquitoes collected from mainland Australia

In response to an incursion of Japanese encephalitis virus (JEV) on Cape York Peninsula, Australia, in 2005, 23,144 Culex mosquitoes were processed for virus detection. A single isolate of JEV was obtained from a pool of Culex sitiens subgroup mosquitoes. This is the first reported mosquito isolate of JEV from the Australian mainland.     

Surveillance of Japanese Encephalitis Virus Infection in Mosquitoes in Vietnam from 2006 to 2008

Japanese encephalitis virus (JEV) infection in mosquitoes was monitored in Vietnam from 2006 to 2008. A total of 15,225 mosquitoes, identified as 26 species in five genera were collected and 12,621 were grouped into 447 pools for examination of JEV infection by assays for cytopathic effects in C6/36 cells and by RT-PCR to detect flavivirus RNA. Three JEV strains were isolated from Culex tritaeniorhynchus Giles collected in northern and southern Vietnam and two JEV strains were isolated from Culex vishnui Theobald collected in the highlands of Vietnam. Genetic and phylogenetic analyses, based on complete E gene nucleotide sequences, revealed that the five JEV strains were classified into the genotype I group and six amino acid differences were found in these five strains. These results indicated that multiple JEV genotype I populations are circulating countrywide in Vietnam, transmitted by bites of their Cx. tritaeniorhynchus and Cx. vishnui.     

First time detection of Japanese encephalitis virus antigen in dry and unpreserved mosquito Culex tritaeniorhynchus Giles, 1901, from Karnal district of Haryana state of India

Japanese encephalitis virus (JEV) antigen has been detected by antigen capture enzyme linked immunosorbentassay (ELISA) in dry specimens of the mosquito Culex tritaeniorhynchus Giles, 1901, collected from Karnal district of Haryana state in northern India. These mosquitoes were stored in dry condition for 20 months, at room temperature, before processing. The procedure of detecting JEV infection in long time stored, dry vector mosquitoes, has important application in the surveillance of Japanese encephalitis.     

A system for studying vector competence of mosquitoes for Japanese encephalitis virus.

A method to infect mosquitoes with Japanese encephalitis virus (JEV) and to demonstrate virus transmission after an extrinsic incubation period is described. Using per oral feeding method infection rate as high as 90% could be achieved. Demonstration of transmission of the virus was achieved by allowing the infected mosquitoes to probe a suitable serum medium and testing the probed serum for virus. Both infection and transmission were demonstrated by using insect-bioassay.     

Application of one step RT-PCR assay for detection of flavivirus RNA in mosquitoes

The conditions of one step RT-PCR method for detection of virus RNA in field-collected mosquitoes, and preservation period of infected mosquitoes for one step RT-PCR were examined. We compared several virus RNA extraction methods with artificially contaminated mosquito pools with dengue virus (DV), Japanese encephalitis virus (JEV), and yellow fever virus (YFV) with a known amount of plaque forming unit (PFU) to establish the condition of one step RT-PCR. In this study, most effective RNA extraction method was ISOGEN-LS extraction combined with supernatant of centrifuged mosquito homogenates. Detection limit of one step RT-PCR using flavivirus universal primer in ten mosquitoes/tube (pool) was 10 PFU of DV, JEV and YFV, 1 PFU of each viruses using species-specific primer respectively, in one hundred mosquitoes/tube, 100 PFU/tube using universal primer pairs, 10 PFU/tube using species-specific primer pairs respectively. Dengue virus infected single mosquito was mixed with 99 un-infected mosquitoes, and tested by one step RT-PCR. We could detect single infected mosquito in pools containing 99 un-infected mosquitoes. Aedes aegypti and Aedes albopictus were inoculated intrathoracically with a mouse-adapted strain of dengue-1 virus and were kept up to 30 days at different temperature. Then examined by one step RT-PCR to determine the appropriate mosquito handling method and the condition of transportation. Positive result was obtained up to 30 days after the mosquito died naturally. These results suggested that we could detect flavivirus RNA tested not only from live mosquitoes but also dead mosquitoes as well, and could apply one step RT-PCR as a rapid, specific, and highly sensitive tool for flavivirus surveillance.     

Desiccated vector mosquitoes used for the surveillance of Japanese encephalitis virus activity in endemic southern India

To monitor Japanese encephalitis virus (JEV) activity in endemic areas of Tamil Nadu, southern India, desiccated vector mosquitoes were screened for JEV antigen using ELISA, from 1996. A total of 133 233 specimens from eight index villages comprising 2816 pools (mainly Culex vishnui subgroup) were tested. Of these, 59 pools (2.1%) were positive for JEV antigen. Control measures were undertaken in positive villages accordingly. The average annual minimum infection rate was 0.8 at the beginning of the study and remained lower for nearly 8 years. A declining trend in JE cases was recorded.     

Distribution of mosquitoes and mosquito-borne viruses along the China-Myanmar border in Yunnan Province

A total of 54,673 mosquitoes were collected at 11 sites located near the China-Myanmar border in the western part of Yunnan Province during July and August 2007. There were 29 species in 4 genera identified from the collections, including 12 species of Culex, 12 species of Anopheles, 3 species of Aedes, and 2 species of Armigeres. Culex tritaeniorhynchus Giles (67.9%, 37,119/54,673) and Anopheles sinensis Wiedemann (25.9%, 14,170/54,673) were the most abundant species in this investigation. Virus was isolated using BHK-21 and C6/36 cells from 22 of 510 mosquito pools. Isolates included Japanese encephalitis virus (JEV) and Getah virus (GETV), which were identified by serological and molecular methods. Twenty JEV strains were isolated from Cx. tritaeniorhynchus (15 isolates), An. sinensis (3 isolates), and Armigeres subalbatus Coquillett (2 isolates), and 2 GETV strains were isolated from Culex pseudovishnui Colless and Cx. tritaeniorhynchus. This study suggests that Ar. subalbatus is a potentially important local vector because of the high JEV infection ratio found in this species. Enzootic JEV transmission persists in this area and therefore, surveillance for human disease caused by JEV and GETV should be conducted in the region.     

Potential for the emergence of Japanese encephalitis virus in California

The potential risk for the introduction and establishment of Japanese encephalitis virus (JEV) within California is described based on the literature. JEV is a mosquito-borne arbovirus endemic to Asia that when transmitted to humans can lead to Japanese encephalitis (JE), a disease affecting mostly children with a fatality rate up to 30%. The geographical expansion of JEV in Asia along with the recent introduction and rapid spread of West Nile virus (WNV) across the United States, demonstrates the ability of arboviruses to rapidly extend their distributions. California is at particular risk for the introduction of JEV because it is a large state functioning as a hub for international travel and commerce with Asia, potentially allowing the introduction of mosquitoes infected with JEV. If JEV is introduced into California, the virus might become established due to the significant number of susceptible mosquito vectors and vertebrate hosts. Once introduced, the lack of active surveillance for JEV, the ambiguous clinical presentation of JE, the cross reactivity of serological testing between JEV and other flaviviruses, and the probability that clinicians and laboratories would not consider JE as a possible diagnosis would likely delay recognition. A significant delay in detection of JEV in California would make control and eradication of the virus very difficult and costly. Public health authorities should consider the need for future control efforts if JEV emerges in the United States.     

Occurrence of Japanese Encephalitis Virus Mosquito Vectors in Relation to Urban Pig Holdings

Japanese encephalitis virus (JEV) is transmitted to humans from pigs or birds by mosquitoes. In this study, the association between urban pig keeping and mosquito vectors was analyzed. A total of 7, 419 mosquitoes were collected overnight in urban households with and without pigs in Can Tho City, Vietnam. The most prevalent vectors were Culex tritaeniorhynchus (36%), Cx. gelidus (24%), and Cx. quinquefasciatus (15%), which were present in all parts of the city. Pigs were associated with increased numbers of Cx. tritaeniorhynchus. Traps close to pigs had higher numbers of Cx. tritaeniorhynchus and Cx. gelidus than traps close to humans. Increased number of persons in the household was associated with increased numbers of Cx. quinquefasciatus. We demonstrate that JEV vector species are present at urban households with and without pigs, and show that keeping pigs in an urban area increase the number of mosquitoes competent as vectors for JEV.