中老边境地区江城县登革热媒介及病毒感染调查

目的了解中老边境江城县登革热媒介的种群密度、孳生习性以及登革病毒自然感染情况,为边境登革热的防控提供参考。方法 2015年6-10月在中老边境江城县选择3个自然村作为固定监测点,采用人诱捕法诱捕白天成蚊,同时在监测点居民区进行幼虫密度和孳生习性调查。捕获的成蚊用液氮低温保存带回实验室用RT-PCR进行登革病毒检测。结果白天人诱法共捕获7属20种2 247只成蚊,其中白纹伊蚊1 405只,占捕获总数的62.53%,其次为骚扰阿蚊438只,占捕获总数的19.49%,未捕到埃及伊蚊,白纹伊蚊成蚊平均密度为16.7只/人工小时;白纹伊蚊幼虫的平均房屋指数、布雷图指数、容器指数和千人指数分别为12.0、18.3、2.2和25.4。8、9月是白纹伊蚊孳生和活动的高峰;白蚊伊纹幼虫以轮胎、罐子和竹筒为主要孳生容器,3种容器占总阳性容器数比例分别为26.3%、23.4%和20.4%;人诱法捕获成蚊RT-PCR检测37组蚊虫,黄病毒属阳性17组,批阳性率为46.0%,未检出登革病毒。结论中老边境江城县登革热传播媒介白纹伊蚊密度较高且分布广,蚊虫携带黄病毒属病毒比例高,应加强当地登革热监测工作。     

福州郊区登革热传播媒介的调查研究

目的　 1999年夏秋季福州郊区发生登革热暴发流行 ,调查本次暴发流行的传播媒介及其生态习性 ,为控制登革热流行提供理论依据。方法　调查流行区媒介伊蚊种类 ,以免疫萤光法检测成蚊病毒自然感染率并判定传播媒介 ;以房屋指数、容器指数和布雷图指数调查幼虫密度 ,以人饵诱捕法人工小时调查成蚊刺叮率 ;调查主要流行村蚊虫孳生环境 ,了解媒介伊蚊孳生现状。结果　白纹伊蚊是当地的优势蚊种 ,埃及伊蚊末捕及 ,成蚊登革病毒 2型自然感染率为 2 3.0 7% ,8个主要流行村白纹伊蚊密度指数平均房屋指数为 5 6 .5 ,容器指数 5 4.5 ,布雷图指数 175 .5 ,刺叮率为 42 .3只。白纹伊蚊的孳生环境类型有 19种 ,主要为闲置的缸、罐类 ,桶类和旧轮胎等各种容器型积水 ,分别占全部阳性积水容器的 2 9.42 % ,17.0 7%和 15 .33%。结论　白纹伊蚊是本次登革热暴发流行的传播媒介 ,当地白纹伊蚊种群密度较高 ,缸、罐类和桶类、旧轮胎等积水容器是白纹伊蚊的主要孳生环境     

大理州12县(市)城区登革热媒介调查结果分析

目的评估大理州12县(市)发生登革热传播风险,为大理州做好登革热防控工作,以应对可能发生来势凶猛的登革热疫情提供科学依据。方法于2016-07/08分别对全州12县(市)县城城区居民区、特殊场所伊蚊幼虫调查。居民区调查:每个县将县城城区按照东、南、西、北、中划分为5个区域,每个区域随机抽取50户作为调查对象,检查每户家中的暂时性积水和永久性积水中的伊蚊幼虫,并吸出所有4龄伊蚊幼虫进行鉴定,计算房屋指数、容器指数、布雷图指数;特殊场所调查:选择城区公园绿地2个、废旧物品回收站不少于10个、轮胎收购站不少于20个和医院2个,开展伊蚊幼虫调查,公园绿地户数折算按每30 m~2折算为1户,计算容器指数、布雷图指数。结果大理州12县市共调查居民区3 014户,仅在洱源县5户5个容器内发现有白纹伊蚊幼虫,其余11县市的居民户均未发现伊蚊幼虫,洱源县居民区除县城中部未捕到白纹伊蚊幼虫外,其余东南西北4个方位均捕到白纹伊蚊幼虫,最高布雷图指数在为4。全州12县市共调查特殊场所274 560 m~2,折合户数9 152户,积水容器9 705个,仅在洱源县的1户1个容器、漾濞县的1户1个容器内发现有白纹伊蚊幼虫,发现白纹伊蚊幼虫的场所均为汽修和轮胎,其余的特殊场所均未发现伊蚊幼虫,洱源县特殊场所最高布雷图指数为5;漾濞县特殊场所最高为6.25。结论大理州暂未发现埃及伊蚊,仅在局部发现少数白纹伊蚊,且密度低,目前各县市城区发生登革热的风险相对较低,但埃及伊蚊在云南的入侵和扩散到大理州的形势十分严峻,登革热是一种传播极易实现的急性蚊媒传染病,需加强监测,以应对可能发生来势凶猛的登革热疫情。县城边缘、汽修和废旧轮胎是白纹伊蚊最适宜孳生环境,为防蚊灭蚊的重点。     

云南西双版纳州勐腊县一起登革热暴发疫情调查分析

目的分析云南省西双版纳州勐腊县2013年1起登革热暴发疫情的流行病学特征,为登革热控制提供依据。方法对所有登革热病例进行流行病学个案调查,疑似病例血清标本采用登革病毒NS1抗原法进行检测,用RT-PCR进行登革热病毒型别鉴定,采用布雷图指数法进行蚊媒密度监测。结果本次疫情流行历时35d,共发现病例44例,其中本地感染病例34例,输入性病例10例(景洪市7例、缅甸2例、老挝1例);病例主要集中在勐腊县城区,共28例,占63.64%(28/44);男女性别比为1.44:1,发病年龄最小4岁、最大75岁,以20~49岁年龄组为主,共33例,占75.00%;职业以农民、商业服务和家政及待业居多;共检出3个登革血清型(Ⅰ型、Ⅱ型和Ⅲ型),其中老挝输入病例为登革病毒Ⅱ型,缅甸输入病例为登革病毒Ⅰ型,其余为登革病毒Ⅲ型。结论该起疫情属于以登革病毒Ⅲ型为主,传播媒介白纹伊蚊和埃及伊蚊并存的暴发疫情。提示今后应进一步加强登革热输入病例的监测和蚊媒控制工作。     

东南亚国家和地区登革热的流行简况

登革热与登革出血热是蚊媒传播疾病，通过埃及伊蚊和白纹伊蚊传播。自１７７９年在印度尼西亚首都雅加达首次流行以来，世界各地陆续有此病的暴发流行，每次患病人数均超过百万。流行区主要分布于热带、亚热带地区，尤以东南亚为重。第二次世界大战后，全球的登革热在东南...     

中越边境地区河口县一起登革热暴发疫情的调查与分析

目的分析中越边境地区河口县一起登革热疫情特点,为制定当地登革热防控措施提供科学依据。方法按登革热诊断标准进行病例诊断,开展流行病学个案调查、病例主动搜索,并采用布雷图指数法及双层叠帐法开展伊蚊幼虫和成蚊应急监测,采用RT-PCR检测疑似登革热病例标本,鉴定登革病毒血清型,综合评价防控效果。结果本次疫情历时49 d,累计报告登革热112例,其中本地病例110例,输入病例2例,主要分布在河口镇,共105例,占93.75%;男性77例(占68.75%),女性35例(占31.25%),男女之比为2.2∶1;发病年龄以20～59岁发病者较多(94例,占83.93%);职业分布以农民为主(38例,占33.93%),其次家务及待业(19例,占16.96%)。捕获白纹伊蚊4只,BI为12.54,HI为7.72%,CI为15.94%。登革病毒血清型为登革病毒1型。结论该起登革热疫情为登革病毒Ⅰ型引起,白纹伊蚊为主要传播媒介,应进一步加强登革热监测和蚊媒控制工作,阻断登革热的传播和流行。     

登革热研究新进展

登革热研究新进展李应光，张继尧，王玉营登革热（ＤＦ）由登革病毒感染所引起，其传播媒介主要是埃及伊蚊和白纹伊蚊。与其它虫媒性疾病相比，该病的发病率和病死率均高得多，全世界每年约２０多亿人受感染威胁［１］；估计每年约发生一亿例登革感染病例［２］，而且该病...     

2021年宁波市白纹伊蚊监测结果分析

目的 分析2021年宁波市白纹伊蚊密度、分布和杀虫剂抗性,为制定登革热防控策略提供科学依据。方法2021年4—11月,于宁波市各县(市、区)均随机选取4个行政村入户调查伊蚊幼虫种群密度,计算布雷图指数(Breteau Index,BI);于各县(市、区)分别选择居民区、公园/竹林、旧轮胎堆放地/废品站/工地等3类生境开展成蚊种群密度调查。2021年6月,于2018年宁波市登革热疫点采集自然品系白纹伊蚊幼虫,经实验室饲养后,分别选取幼虫和未吸血雌蚊开展抗药性实验,对照组蚊虫为白纹伊蚊杀虫剂敏感品系。其中幼虫以浸渍法测定对溴氰菊酯、高效氯氰菊酯、残杀威、双硫磷和敌敌畏抗药性,计算半数致死浓度(medium lethal concentration,LC₅₀)和抗性倍数(resistance ratio,RR);成虫以接触筒法测定对高效氯氰菊酯、氯菊酯、溴氰菊酯、残杀威和马拉硫磷抗药性,计算死亡率。结果 2021年宁波市累计调查9 935户10 072个小型积水容器,其中伊蚊幼虫阳性容器1 276个,平均BI为12.89;共布帐1422顶,捕获雌性白纹伊蚊954只,平均...     

老挝登革热流行特征研究进展

登革热是由携带登革病毒的白纹伊蚊或埃及伊蚊叮咬人类传播的一种重要虫媒传染病,主要流行在热带亚热带国家或地区。老挝登革热流行较为严重,1979年首次报道登革热病例,并自2008年起,建立了国家登革热数据报告系统,近年来,通过大量的登革热疫情特点、登革热媒介调查、登革病毒血清型监测及其防控措施等研究,基本弄清了老挝登革热流行特征,本文对老挝登革热流行特征研究进展进行综述。     

南昌市登革热传播媒介白纹伊蚊密度、抗药性及病原体携带监测研究

目的 掌握南昌地区白纹伊蚊密度、季节消长规律、登革热病毒携带以及对常用杀虫剂的抗药性程度,为合理选择和使用杀虫剂,科学防控登革热提供科学依据。方法 采用WHO推荐的幼虫浸渍法和成蚊接触筒法分别测定白纹伊蚊幼虫和成蚊的抗药性;密度监测:成蚊采用双层叠帐法,幼虫分别采用布雷图指数法(BI)、勺舀法和路径指数法;白纹伊蚊登革热病毒携带检测采用RT-PCR核酸检测。结果 2018年南昌地区白纹伊蚊成蚊呈单峰活动趋势,活动最高峰为6月份,全年平均帐诱指数为2.76只/(顶·h),平均布雷图指数(BI)为6.18,平均路径指数为4.67处/km,居民区帐诱指数、BI和路径指数远高于工地和公园生境。白纹伊蚊成蚊对溴氰菊酯和高效氯氰菊酯产生抗性,对马拉硫磷、氯菊酯、杀螟硫磷和残杀威表现敏感;白纹伊蚊幼虫除对溴氰菊酯表现为敏感外,对DDVP等其他6种杀虫剂分别表现出不同的抗性,抗性倍数处于9.09~76.19之间。南昌地区野外品系白纹伊蚊未检测到登革热病毒。结论 一旦有登革热病例的输入,南昌地区存在登革热传播风险, 应停用已产生高度抗药性的氯氰菊酯、残杀威等杀虫剂,重点清除居民区生境内白纹伊蚊孳生地,及时根据监测结果评估登革热发生或流行的风险,可为南昌地区登革热疫情的预测预警提供科学依据。     

Entomologic investigations of a chikungunya virus epidemic in the Union of the Comoros, 2005

From January to April 2005, an epidemic of chikungunya virus (CHIKV) illness occurred in the Union of Comoros. Entomological studies were undertaken during the peak of the outbreak, from March 11 to March 31, aimed at identifying the primary vector(s) involved in transmission so that appropriate public health measures could be implemented. Adult mosquitoes were collected by backpack aspiration and human landing collection in homes and neighborhoods of clinically ill patients. Water-holding containers were inspected for presence of mosquito larvae. Adult mosquitoes were analyzed by RT-PCR and cultivation in cells for the presence of CHIK virus and/or nucleic acid. A total of 2,326 mosquitoes were collected and processed in 199 pools. The collection consisted of 62.8% Aedes aegypti, 25.5% Culex species, and 10.7% Aedes simpsoni complex, Eretmapodites spp and Anopheles spp. Seven mosquito pools were found to be positive for CHIKV RNA and 1 isolate was obtained. The single CHIKV mosquito isolate was from a pool of Aedes aegypti and the minimum infection rate (MIR) for this species was 4.0, suggesting that Ae. aegypti was the principal vector responsible for the outbreak. This was supported by high container (31.1%), household (68%), and Breteau (126) indices, with discarded tires (58.8%) and small cooking and water storage vessels (31.1%) registering the highest container indices.     

Surveillance of dengue fever cases using a novel Aedes aegypti population sampling method in Trinidad, West Indies: the cardinal points approach

A novel dengue surveillance method is described and used to evaluate 100 suspected dengue fever (DF) cases in county St. Patrick, Trinidad, West Indies. From the 30 confirmed DF cases fully investigated within 48 h of diagnosis, 63% (19/30 houses) of their homes were found harboring Aedes aegypti immature stages. Only houses at the four cardinal points of the index case rather than the entire neighborhood were investigated. The results showed significantly (P<0.001) more Ae. aegypti positive houses were observed to the east (P<0.04) and west (P<0.01) than to the north and south (P>0.9). In addition, from the 150 houses inspected a total of 474 artificial containers were inspected and treated, of which 20.8% (99) were infested with Ae. aegypti immature stages. More than 49% of the containers inspected were small miscellaneous containers, but they only produced 4.0% of the Ae. aegypti immatures, of which only 0.4% were pupae. Water tanks (41.7%), drums (40.4%) and buckets (24.2%) produced over 98% of the pupae. The results of this study imply that dengue vector control programs in Trinidad could increase their efficiency by applying the cardinal points surveillance approach during DF case investigations and concentrating their vector control measures on the most productive containers located at the east and west of the index cases.     

Distribution and seasonality of vertically transmitted dengue viruses in Aedes mosquitoes in arid and semi-arid areas of Rajasthan, India

BACKGROUND & OBJECTIVES: Transovarial transmission of dengue virus is a crucial etiological phenomenon responsible for persistence of virus during inter-epidemic period of the disease. Distribution and seasonality of this phenomenon in disease endemic areas may contribute to explain emergence of dengue and its subsequent prevention. The study on seasonal and area distribution of transovarial transmission of dengue virus in Aedes aegypti, Ae. albopictus and Ae. vittatus has been made in desert and non-desert districts of Rajasthan, India from 2006 to 2007. The observations revealed role of different Aedes species in transmission and retention of dengue virus. METHODS: The larvae of Ae. aegypti, Ae. albopictus and Ae. vittatus were collected during each of the study seasons from rural and urban areas of three districts-Jodhpur, Jaipur and Kota. The larvae were collected from domestic and peri-domestic containers and from tree holes of peri-urban foci such as gardens and parks and were reared into adults in the laboratory at room temperature. The laboratory reared adults were subjected to Indirect fluorescence antibody test (IFAT). The laboratory-reared adult mosquitoes showing positive IFA were treated as the sample showing vertically transmitted dengue virus. RESULTS: Pooled data for all the four seasons revealed maximum (15.7%) mosquito infectivity in Ae. albopictus followed by Ae. aegypti (12.6%) in Jodhpur district. In Jaipur district, Ae. vittatus showed highest infection (20%) of vertically transmitted virus followed by Ae. albopictus (18.7%) and least in Ae. aegypti (13.3%). In Kota district, pooled data for all the four seasons showed maximum vertical infection of mosquitoes in Ae. albopictus (14.2%). INTERPRETATION & CONCLUSION: Transovarial transmission of dengue virus by available vector species in a dengue endemic setting could be the key etiological phenomenon responsible for re-emergence of the disease from inter-epidemic to epidemic phase of disease onset. The observations in the present study suggest that during winter season which is not the active transmission season of dengue in Rajasthan, Ae. albopictus has shown maximum percentage of vertically transmitted virus. Our observation substantiates with the earlier studies that how Ae. albopictus is horbouring virus during inter-epidemic period of dengue. Another important lead emerging through present study is the high mosquito infectivity of Ae. aegypti during summer and rainy seasons especially from desert districts, Jodhpur and semi district. This observation suggests that in Rajasthan, owing to tendency of overstorage of domestic water by the inhabitants, mosquito and vertically transmitted virus get pronounced during summer season which could precedes the active transmission season of dengue during following rainy season.     

Characteristics of the spatial pattern of the dengue vector, Aedes aegypti, in Iquitos, Peru

We determine the spatial pattern of Aedes aegypti and the containers in which they develop in two neighborhoods of the Amazonian city of Iquitos, Peru. Four variables were examined: adult Ae. aegypti, pupae, containers positive for larvae or pupae, and all water-holding containers. Adults clustered strongly within houses and weakly to a distance of 30 meters beyond the household; clustering was not detected beyond 10 meters for positive containers or pupae. Over short periods of time restricted flight range and frequent blood-feeding behavior of Ae. aegypti appear to be underlying factors in the clustering patterns of human dengue infections. Permanent, consistently infested containers (key premises) were not major producers of Ae. aegypti, indicating that larvaciding strategies by themselves may be less effective than reduction of mosquito development sites by source reduction and education campaigns. We conclude that entomologic risk of human dengue infection should be assessed at the household level at frequent time intervals.     

Epidemiological and entomological investigation in dengue outbreak area of Ahmedabad district

Epidemiological and Entomological investigations conducted in seven affected villages of Sanand and Viramgam Talukas of Ahmedabad district revealed that all age groups and both the genders were affected. 33.33% blood samples of patients showed seropositivity suggesting dengue infection Similarly, Dengue virus antigen was detected in 7 Females Ae. aegypti out of 2 Males and 26 Females tested by indirect immunofluroscent technique. Aedes aegypti population measured by various parameters i.e. Premise index (32.16%), Receptacle index (26.15%) and infested receptacle index (0.36%) were above the critical limit. Aedes aegypti population is susceptible to 5% Malathion. The findings suggest the fever outbreak was of dengue. Co-related evidences indicated the possible role of dengue 2 virus in the outbreak.     

An ecological survey of dengue vector mosquitos in central Lao PDR

An ecological survey of dengue vector mosquitos was carried out in June 2000 in central Lao PDR. Two areas in Khammouane Province, Nongbok and Thakhek, were selected for the survey. Of the 7 mosquito species identified, Aedes aegypti was dominant in both study areas. The container index for Ae. aegypti in Nongbok was 51.8% and was significantly higher than that of Thakhek (40.2%); moreover, significant differences between the study areas were found with records to containers and to the conditions surrounding the houses. The key containers in Nongbok were water jars, whereas drums or small or discarded containers had the highest occurrence rate of Ae. aegypti in Thakhek. Mesocyclops aspericornis was found in large water jars and cement water tanks; no Aedes larvae were found at these sites. Strategy to control dengue vectors in the study areas was discussed.     

Dengue knowledge and practices and their impact on Aedes aegypti populations in Kamphaeng Phet, Thailand

A knowledge, attitude, and practice (KAP) survey and an extensive entomologic survey were conducted in two sub-districts of Kamphaeng Phet province, Thailand, to test the hypothesis that correct dengue knowledge and practice reduce dengue vector populations. We found a negative association between respondents' knowledge of preventive measures and the number of unprotected containers in and around their houses. Knowledge of development sites was positively associated with unprotected containers. No relationships existed between knowledge of dengue and adult mosquito reduction practices. A higher number of unprotected containers increased the likelihood of the house being infested with one or more adult Aedes aegypti. Surprisingly, houses of respondents that used mosquito coils or had screening on doors and windows were significantly more likely to be infested (odds ratio =2.0) with adult Ae. aegypti. We conclude that there is a direct link between knowledge on dengue prevention and container protection practices, whereas measures against adult mosquitoes are used only when people experience a mosquito nuisance problem.     

Infection of adult Aedes aegypti and Ae. albopictus mosquitoes with the entomopathogenic fungus Metarhizium anisopliae

This study describes a laboratory investigation on the use of the insect-pathogenic fungus Metarhizium anisopliae against adult Aedes aegypti and Ae. albopictus mosquitoes. At a dosage of 1.6 x 10(10)conidia/m(2), applied on material that served as a mosquito resting site, an average of 87.1+/-2.65% of Ae. aegypti and 89.3+/-2.2% of Ae. albopictus became infected with the fungus. The life span of fungus-contaminated mosquitoes of both species was significantly reduced compared to uninfected mosquitoes. LT(50)-values of fungus-contaminated mosquitoes ranged between 3.1+/-0.2 days (male Ae. aegypti) and 4.1+/-0.3 days (female Ae. aegypti). LT(50)-values of uncontaminated mosquitoes ranged from 17.7+/-0.4 days (female Ae. albopictus) to 19.7+/-0.6 days (male Ae. albopictus). These results indicate that both mosquito species are highly susceptible to infection with this entomopathogen. Requirements for developing and incorporating this biological control method into current strategies to control major diseases vectored by these species, such as dengue fever, are discussed.     

Use of the pupal/demographic-survey technique to identify the epidemiologically important types of containers producing Aedes aegypti (L.) in a dengue-endemic area of Venezuela

As dengue continues to emerge as a major public-health problem world-wide, efforts to control the dengue vector Aedes aegypti must become more effective and efficient. Results from larval and pupal surveys applied in Venezuela illustrate the uniqueness of the information gained from pupal surveys; information that is lost when traditional Stegomyia indices are calculated. As most Ae. aegypti pupae will emerge to become adults, controlling the containers that produce the most pupae could have the greatest impact on the adult population. Pupal-survey results in Venezuela showed that large (150- to 200-litre) water drums produce the greatest number of pupae throughout the year. In the rainy season, approximately 70% of all pupae are found in these drums or in tyres, buckets and tanks. Over 80% of pupae in the dry season are found in drums and tanks alone. By targeting only those domestic breeding containers that produce the greatest number of pupae, control efforts may be streamlined to have the greatest impact on reducing the local adult Ae. aegypti population.     

Epidemic dengue and dengue hemorrhagic fever at the Texas-Mexico border: results of a household-based seroepidemiologic survey, December 2005

A dengue-2 epidemic causing dengue hemorrhagic fever (DHF) occurred in the contiguous border cities of Matamoros, Tamaulipas (Mexico), and Brownsville, TX, in 2005. In December, we conducted a household-based epidemiologic survey to determine the incidence and seroprevalence of dengue infection among Matamoros and Brownsville residents and to identify risk factors associated with infection. Antibodies to dengue were measured in 273 individuals. The estimated incidence of recent dengue infection was 32% and 4% among Matamoros and Brownsville participants, respectively. The estimated prevalence of past dengue infection was 77% and 39% among Matamoros and Brownsville participants, respectively. The Breteau index was 28 in Matamoros and 16 in Brownsville, reflecting an abundant winter population of Aedes mosquitoes. Discarded waste tires and buckets were the two largest categories of infested containers found in both cities. Our results underscore the risk for epidemic dengue and DHF in the Texas-Mexico border region.