福建株白纹伊蚊经口感染登革2型病毒研究

目的 探讨福建株白纹伊蚊对登革2型病毒的易感性。方法 用C6/36细胞培养登革2型病毒,白纹伊蚊人工经口感染病毒混合液,14 d后分别用间接免疫荧光和RT PCR检测蚊体内的登革2型病毒。结果 用间接免疫荧光检测感染登革2型病毒的白纹伊蚊,福建株白纹伊蚊感染率为44.6%（25/56）,头部感染率为32.1%（18/56）;用RT-PCR方法扩增出511 bp片段,感染率为53.9%（14/26）。结论 福建株白纹伊蚊对登革2型病毒易感。     

白纹伊蚊经滞育卵传递登革Ⅱ型病毒的实验研究

目的　证明登革Ⅱ型病毒能否在白纹伊蚊滞育卵内存活并传至子代。方法　采用逆转录 -聚合酶链反应检测病毒 ,C6 36细胞培养分离病毒。结果　能在白纹伊蚊滞育卵内检测到病毒 ,且滞育卵解除滞育后 ,子 1代幼虫和成蚊中均检测到病毒 ,总的批阳性率为 9.6 % ,子代最低感染率为 1∶2 94.3 ;第一个生殖营养周环子代未分离到病毒 ;第二、三生殖营养周环子代间最低感染率差异无显著性 ( χ2 =0 .0 1,P >0 .0 5 )。结论　试验证明登革Ⅱ型病毒能在白纹伊蚊滞育卵内存活并传至子代。     

云南白纹伊蚊感染,传播登革和乙型脑炎病毒的研究

云南株白纹伊蚊通过吸食含病毒的血餐或叮吸有病毒血症的小鸡血，能感染登革和乙型脑炎病毒，并能在蚊体内增殖。感染蚊经叮咬吸血，能将这两种病毒传播给乳鼠或小鸡。雌蚊感染后第10天，对乳鼠的传播率登革1、2、3、4型和乙型脑炎依次为22．22％、37．50％、25．00％、44．44％和37．50％；对小鸡的传播率登革4型和乙型脑炎分别为100％和66．67％。实验结果表明，白纹伊蚊在登革和乙型脑炎病毒保存和传播中起重要作用。     

用随机扩增多态DNA(RAPD)技术研究不同地理株埃及伊蚊的分化

目的 用RAPD技术对实验室饲养的广东、海南、台湾和印尼Baro等4个不同地理株的8只雌蚊进行随机扩增多态DNA分析。方法 随机扩增多态性DNA(RAPD)技术。结果 选用20个随机引物进行扩增，有8个引物表现清晰的RAPD谱带并呈显著多态性。UPGMA法构建的分子系统树表明埃及伊蚊4个地理株之间存在着一定程度的遗传分化。结论 用RAPD方法可以区分不同地理株埃及伊蚊。     

云南白纹伊蚊分布特点及与虫媒病毒的关系

目的：阐明白纹伊蚊分布特点,掌握其自然感染虫媒病毒情况,方法;白天在居民点周围和野外竹林区捕蚊,用细胞法和乳鼠法分离病毒。结果：采获成年雌性蚊虫8属45种24885只,其中白纹伊蚊7622只,占30．62％,从该蚊中分离到登革4型病毒4株,登革3型病毒1株,流行性乙型脑炎病毒2株,基孔肯雅病毒2株,]甲病毒2株。结论：白纹伊蚊在云南广泛分布,属竹林区优势蚊种,是云南登革热和基孔肯雅病的主要传播媒介及流行性乙型脑炎的传播媒介。     

广西登革热流行概况及分析

1980年6～11月在广西沿海合浦、钦州两县由登革Ⅲ型病毒引起首次登革热流行,疫点发病率分别为44．21％、57．41％。1986年9～11月在北海市发生第二次流行,流行株为登革Ⅱ型病毒,疫点发病率为12．60％,1987年7月在内陆地区玉林市报告1例Ⅱ型病毒感染的病例,1988年至今未见有病例报告。流行病学资料分析结果：各年龄组普遍易感;两次流行与海南疫情关系密切;传播媒介,合浦县为埃及伊蚊,钦州县、北海市为白纹伊蚊;实施化学方法和清除伊蚊孳生地的灭蚊后,经1～2个潜伏期即可终止流行。     

云南省耿马县孟定镇蚊虫及虫媒病毒调查

目的 :调查蚊虫种类及其带病毒情况。方法 :用吸蚊管和人诱法捕蚊 ,用C6 / 36细胞和乳鼠分离病毒 ,用血清学方法检测人血清中病毒抗体。结果 :1985年 7～ 8月捕获雌性成蚊 6属32种 94 10只 ,三带喙库蚊、棕头库蚊、中华按蚊、迷走按蚊是农村畜厩主要蚊种 ,白纹伊蚊是竹林区优势蚊种。从阿萨姆伊蚊中分离出 1株乙脑病毒。当地人血清中乙脑、登革、基孔肯雅和肾综合征出血热 (HFRS)病毒抗体阳性率依次为 39.6 8% (77/ 194 )、13.73% (14/ 10 2 )、2 0 .10 % (39/ 194 )和 0 .57% (1/ 94 )。结论 :云南耿马县孟定镇存在乙脑和其它虫媒病毒病     

致倦库蚊传播登革病毒可能性的实验研究

目的：在实验室通过病毒分离和传播试验,确定致倦库蚊是否能传播登革病毒。方法：１．用大剂量登革Ⅱ型病毒（病毒滴度为１０＾－９～１０＾－１０ＴＣＩＤ５０）同时喂食致倦库蚊和白纹伊蚊,不同时间后用Ｃ６／３６细胞从蚊体内分离登革病毒。２．用吸食病毒７ｄ后的致倦库蚊和白纹伊蚊攻击小白鼠１ｄ龄乳鼠,两周后取鼠血清进行免疫荧光试验。结果：１３ｄ内不同时间均能从白纹伊蚊体内分离出登革病毒,而致倦库蚊在４８ｈ以后不     

我国不同地理株白纹伊蚊对登革病毒的易感性

本文用棉球病毒悬液法感染白纹伊蚊,比较了我国9个不同地理株白纹伊蚊对经口感染登革病毒Ⅰ、Ⅱ和Ⅳ型的易感性。实验结果表明,我国不同地理株白纹伊蚊对经口感染登革病毒的易感性有差别。海口株对三个血清型登革病毒均较易感,北京株和成都株分别对登革病毒Ⅰ型和Ⅱ型较易感,各地理株白纹伊蚊对登革病毒Ⅱ型的易感性普遍较高。本文还用蚊胸内病毒接种技术,比较了我国9个不同地理株白纹伊蚊对胸内接种感染登革病毒Ⅰ、Ⅱ和Ⅳ型的易感性,结果胸内接种各型登革病毒的易感性未见明显差异,提示经口感染易感性的差别是中肠屏障的作用。本文所采用的蚊脑涂片间接免疫荧光技术检测蚊脑内登革病毒抗原的方法,蚊脑组织在玻片上分布较均匀,可避免蚊头外骨骼对脑组织的遮盖,似比蚊头压片法易于观察结果,有利于提高检出率。     

以免疫荧光检测蚊体内登革抗原的简易方法

将四种血清型登革病毒的任何一种,感染雄性或雌性白纹伊蚊,并压碎头部,以直接荧光抗体检查,可测出登革抗原。从而把试验材料经肠道外接种于蚊体,可以迅速而简易地分离到登革病毒。用肠道外接种雄蚊或雌蚊法来分离或繁殖登革病毒,可以极大地促进这一人类重要疾病的病原工作。虽然,曾用细胞培养法来发现受染昆虫中病毒的存在,但为了简化病毒分离程序和缩短识别受染蚊的时间,我们探求使用荧光抗体技术。本文描述直接荧光抗体技术来发现蚊体中登革抗原的经过和评价.     

Intrinsic features of Aedes aegypti genes affect transcriptional responsiveness of mosquito genes to dengue virus infection

Dengue virus infection causes significant morbidity and mortality in humans world-wide. The Aedes aegypti mosquito is the major vector that spreads dengue virus to humans. Interaction between dengue viruses and A. aegypti is a multi-factorial phenomena that is determined by both virus and mosquito genotypes. Although, studies have suggested significant association of mosquito vectorial capacity with population variation of dengue virus, specifications of the vector factors that may influence vector-virus compatibility are very limited in the literature. Recently, we have shown that a large number of genes are differentially expressed between MOYO-S (susceptible) and MOYO-R (refractory) A. aegypti strains upon infection with dengue virus (JAM-1409 genotype). In the current study, we show that specific intrinsic features of A. aegypti genes are significantly associated with 'responsiveness' of mosquito genes to dengue infection. Binomial logistic regression analysis further reveals differential marginal effects of these features on gene responsiveness of mosquitoes to the viral infection. Thus, our result shows that intrinsic features of genes significantly affect differential expression of A. aegypti genes to dengue infection. The information will benefit further investigations on evolution of genes among natural populations of A. aegypti conferring differential susceptibility to dengue virus.     

Variation in the vector competence of geographic strains of Aedes albopictus for dengue 1 virus

Eight geographic strains of Aedes albopictus from Asia and North America and one North American strain of Aedes aegypti were tested for their vector competence with dengue 1 virus. Three groups of Ae. albopictus were established based on their vector competence: a) the OAHU laboratory strain, b) the three Malaysian strains, and c) the TOKYO and three North American strains. The three North American strains were similar to the strain of Ae. aegypti from Houston, Texas in their ability to transmit dengue 1 virus. A comparison of barriers to infection and transmission suggests that Ae. albopictus HOUSTON represents an introduced strain distinct from the more similar MEMPHIS and NEW ORLEANS strains. Based on these studies the North American strains were seen as more similar to a northern Asian strain (TOKYO) than to the three Malaysian (southern Asia) strains, supporting the current hypothesis that the indigenous strains of Ae. albopictus recently introduced into the United States had a northern Asian origin.     

Vector competence of Aedes aegypti populations from Senegal for sylvatic and epidemic dengue 2 virus isolated in West Africa

Vector competence of Aedes aegypti populations from six locations in different bioclimatic zones and habitats of Senegal was assessed for sylvatic (ArD 140875) and epidemic (ArA 6894) dengue 2 virus (DENV-2) isolates. F1 generation mosquitoes were fed with a blood meal containing 10(6.5) and 1.6 x 10(7) tissue culture infectious dose (TCID50) of the sylvatic DENV-2 isolate or 10(6.5) TCID50 of the epidemic isolate and incubated for 14 days. After this period, legs and wings of each individual were pooled and the corresponding body was collected separately. An immunofluorescence assay was used to test bodies and wings/legs for DENV-2 infection separately. The results showed that: (i) Senegalese Ae. aegypti populations have lower vector competence (infection rate 0-26%, dissemination rate 10-100%) for sylvatic and epidemic dengue viruses than populations from Asia and America; (ii) there was no obvious geographic variation in susceptibility among mosquito populations; (iii) the only apparent factor affecting the susceptibility was the virus titre; and (iv) except for that of Kédougou, all populations were able to disseminate the virus. Overall our findings, while extended to four other populations, confirm previous studies showing low susceptibility of Senegalese Ae. aegypti populations.     

Aedes albopictus from Albania: a potential vector of dengue viruses

Aedes albopictus collected in Durazzo, the main port of Albania, were tested for oral susceptibility to dengue type 2 virus and their infection rates were compared to those of an Aedes aegypti strain (Paea) and another strain of Ae. albopictus (Tananarive). Infection rates for the Albanian Ae. albopictus were dose dependent, ranging from 38.9 +/- 13.6% to 85.1% with the titer of the meal increasing from 10 x 8.1 to 10 x 9.1 50% mosquito infectious doses (MID50)/ml. The percentage of infected females was lower for the Ae. albopictus Durazzo strain than for the Ae. aegypti Paea strain: 38.9 +/- 13.6% compared with 92.4 +/- 4.9% for a meal of 10 x 8.1 MID50/ml, respectively. However, the difference was less when the titer of the meal was increased: 85.1% compared with 100% for a meal of 10 x 9.1 MID50/ml, respectively. The infection rate was also lower for the Durazzo strain than for the Tananarive strain of Ae. albopictus. The degree of viral replication in infected females was not significantly different in the 3 strains tested and we were able to demonstrate the ability of females from the Durazzo strain to transmit the virus in the course of a blood meal. Our results lead us to conclude that Ae. albopictus from Albania could serve as a vector for dengue virus.     

Dengue emergence and adaptation to peridomestic mosquitoes

Phylogenetic evidence suggests that endemic and epidemic dengue viruses (DENV), transmitted among humans by the anthropophilic mosquitoes Aedes aegypti and Ae. albopictus, emerged when ancestral, sylvatic DENV transmitted among nonhuman primates by sylvatic Aedes mosquitoes adapted to these peridomestic vectors. We tested this hypothesis by retrospectively examining evidence for adaptation of epidemic and endemic versus sylvatic strains of DENV-2 to Ae. albopictus and Ae. aegypti. First and second-generation offspring of mosquitoes from different geographic regions in the Americas and Southeast Asia were tested for their susceptibility to epidemic/endemic and sylvatic DENV-2 isolates from West Africa, Southeast Asia, and Oceania. Both Aedes species were highly susceptible (up to 100% infected) to endemic/epidemic DENV-2 strains after ingesting artificial blood meals but significantly less susceptible (as low as 0%) to sylvatic DENV-2 strains. Our findings support the hypothesis that adaptation to peridomestic mosquito vectors mediated dengue emergence from sylvatic progenitor viruses.     

Infection and dissemination of dengue virus type 2 in Aedes aegypti, Aedes albopictus, and Aedes scutellaris from the Torres Strait, Australia

To determine their relative roles in transmission of dengue virus (DENV) in the Torres Strait region of northern Australia, we examined infection and dissemination of a sympatric strain of dengue virus type 2 (DENV-2) in Aedes scutellaris, Ae. albopictus, and Ae. aegypti. In experiments using membrane feeders for virus exposure, infection rates were 83% and 43% for Ae. scutellaris and Ae. aegypti, respectively. Salivary gland infection rates for both species were 43%. In experiments using pledgets for virus exposure, infection rates for Ae. aegypti, Ae. scutellaris, and Ae. albopictus were 68%, 55%, and 37%, respectively. Aedes albopictus exhibited the greatest barriers to infection with only 7% tested developing a salivary gland infection, compared to 42% and 24% of Ae. aegypti and Ae. scutellaris, respectively. These results suggest that Ae. scutellaris may have been responsible for DENV transmission on Torres Strait islands, where Ae. aegypti does not occur. In contrast, Ae. albopictus may not be an important vector of DENV-2 from the Torres Strait.     

Vector competence of Aedes albopictus from Houston, Texas, for dengue serotypes 1 to 4, yellow fever and Ross River viruses

A combination of virus infection and transmission experiments showed that a Houston, Texas strain of Aedes albopictus is a competent vector for dengue (DEN), yellow fever (YF) and Ross River (RR) viruses. However, at 14 days incubation, DEN virus infection rates in a Puerto Rican strain of Aedes aegypti were significantly higher for each of the four DEN serotypes, except DEN-1, than in Houston Ae. albopictus fed simultaneously on the same virus suspensions. The degree of correlation between disseminated DEN infection rates in Houston Ae. albopictus and transmission to an in vitro system ranged from 42 to 88% for the four DEN serotypes. No significant difference was noted in YF virus infection rates or transmission rates in the two mosquito species fed on the same virus suspensions and incubated for the same time period. Also, RR virus infection and transmission rates in Houston and Hawaiian strains of Ae. albopictus were generally comparable.     

Aedes aegypti in Brazil: genetically differentiated populations with high susceptibility to dengue and yellow fever viruses

Aedes aegypti was eliminated from Brazil in 1955, but re-infested the country in the 1970s. Dengue outbreaks have occurred since 1981 and became endemic in several cities in Brazil after 1986. Urban yellow fever has not occurred since 1942, and only jungle yellow fever cases have been reported. A population genetic analysis using isoenzyme variation combined with an evaluation of susceptibility to both yellow fever and dengue 2 viruses was conducted among 23 A. aegypti samples from 13 Brazilian states. We demonstrated that experimental infection rates of A. aegypti for both dengue and yellow fever viruses (YFV) are high and heterogeneous, and samples collected in the endemic and transition areas of sylvatic yellow fever were highly susceptible to yellow fever virus. Boa Vista, a border city between Brazil and Venezuela, and Rio de Janeiro in the Southeast region are considered as the most important entry points for dengue dissemination. Considering the high densities of A. aegypti, and its high susceptibility to dengue and yellow fever viruses, the risk of dengue epidemics and yellow fever urbanization in Brazil is more real than ever.