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.     

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。     

白纹伊蚊传播登革病毒的媒介效能研究

目的：研究白纹伊蚊在登革病毒传播中的作用。方法：应用Ｃ６／３６细胞培养病毒结合ＲＦＰＣＲ检测,用间接免疫荧光法（ＩＦＡ）检测血清抗体。结果;饱吸感染发病乳鼠血的白纹伊蚊,对ＤＥＮ１～４型有较高的感染率（５０％～５８％）,通过叮咬敏感动物（乳鼠）也能传播这４个型的ＤＥＮ。分批检测感染雌蚊的子１代卵、幼虫及雌、雄成虫,证实白纹伊蚊能经卵传递ＤＥＮ,至少可舒心代以上。结论：该地ＤＥＮ有较大的媒介效能,且     

中缅边境地区孟连和澜沧县登革热媒介蚊虫调查

目的了解中缅边境地区孟连和澜沧县登革热媒介种类、生态习性和登革热病毒自然感染状况,为登革热预防控制提供科学依据。方法在孟连和澜沧县选择3个自然村作为监测点,采用人工诱捕法白天诱捕成蚊,并在房屋内外积水容器捕捞幼虫,采用RTPCR方法对现场捕获的成蚊进行登革热病毒检测。结果 2010年6-10月在孟连和澜沧县监测点共捕获蚊虫6属8亚属22种3436只,其中白纹伊蚊为优势蚊种,占捕蚊总数的33.82%;未捕到埃及伊蚊。3个观察点白纹伊蚊平均房屋指数19.3,容器指数5.84,布雷图指数30.3,千人指数68.5;白纹伊蚊孳生环境类型以竹筒、土罐类和旧轮胎等临时积水容器为主,分别占阳性积水容器数的34.1%、27.5%和17.6%;白纹伊蚊成蚊平均密度为8.98只/人工小时;成蚊密度高峰出现在7-8月;对捕获的29批白纹伊蚊(1162只)进行RTPCR检测,未发现登革热病毒感染。结论白纹伊蚊密度较高且分布广泛,应加强当地登革热监测工作。     

白纹伊蚊对登革病毒垂直传递能力研究

目的利用细胞及分子生物学技术，研究白纹伊蚊贵州省贵阳、兴义、毕节株对1—4型登革病毒（DEN1—4）的垂直传递能力。方法采集贵州省贵阳、兴义、毕节市市郊自然界白纹伊蚊，驯化3代。分别取羽化后3～5d龄成蚊为实验组，白纹伊蚊海南株为对照组；用DEN1—4国际参考株分别感染各组蚊虫，将感染后亲代及子1～3代成蚊制备蚊悬液，接种C6／36进行病毒分离并鉴定；间接免疫荧光法检测DEN抗原；常规方法提取总RNA。利用DENNS1基因区通用引物经逆转录-聚合酶链反应（RT—PCR）检测DEN核酸，限制性内切酶酶切分型。结果白纹伊蚊贵阳、兴义、毕节、海南株亲代蚊虫均对DEN易感；白纹伊蚊兴义株与海南株均能垂直传递DEN-1、4到子3代。传递DEN-3到子2代，白纹伊蚊兴义株能垂直传递DEN-2到子3代，白纹伊蚊贵阳．株能垂直传递DEN-1到子3代，传递DEN-2、3、4到子2代，白纹伊蚊毕节株能垂直传递DEN-1到子2代，DEN-4至子3代，未发现能垂直传递DEN-2、3。结论对DEN1—4易感的白纹伊蚊贵阳、兴义、毕节株能垂直传递DEN，且对DEN的垂直传递能力与其地理来源有关；贵州省3个地方株的白纹伊蚊卵可在干燥室温条件下越冬保存DEN。     

Temporal abundance,parity, survival rates,and arbovirus isolation of field-collected container-inhabiting mosquitoes in eastern Tennessee

Surveillance of container-inhabiting mosquitoes was conducted from June 17 through November 9, 1998, at 2 1997 La Crosse virus (LAC) human case sites (Knox and Cocke counties, Tennessee). Mosquitoes were collected weekly with 2 dry ice-baited Centers for Disease Control miniature light traps, 2 omnidirectional Fay traps, and 40 oviposition traps at each site. A total of 8,408 mosquitoes, composed of Ochlerotatus triseriatus (n = 2,095) and Aedes albopictus (n = 6,313), were reared or collected and assayed for virus. The majority of host-seeking Ae. albopictus (n = 567) collected from July through October from both sites were dissected to determine parity status. Monthly parity rates ranged from 0.78 to 0.85 and 0.79 to 0.92 in Knox and Cocke counties, respectively. The high parity rates indicate that this population of Ae. albopictus has a high daily survival rate and may have a high vector potential. The temporal patterns in Ae. albopictus and Oc. triseriatus egg collections from both of the human case sites were significantly correlated, suggesting that the populations fluctuate in a similar manner across the eastern Tennessee region. Although LAC was not isolated from either species, one isolation of a California serogroup virus, most likely a subtype of Jamestown Canyon virus (JC), was recovered from a pool of 50 male Ae. albopictus reared from eggs collected at the Knox County site (minimum field infection rate of 1.89 per 1,000). This is the 1st report of a very closely related JC-like virus in Ae. albopictus and from Tennessee, as well as the 1st time this potential human pathogen has been isolated from transovarially infected field populations of Ae. albopictus.     

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.     

A comparison of seven traps used for collection of Aedes albopictus and Aedes aegypti originating from a large tire repository in Harris County (Houston), Texas

Among 7 traps tested, significantly higher (P < 0.01) mean numbers of Aedes albopictus (269) and Aedes aegypti (55) females were collected within the Mosquito Magnet Liberty trap compared with the remaining traps. The second highest mean captures for both species were obtained from omnidirectional Fay-Prince (77 Ae. albopictus) and Dragonfly (13 Ae. aegypti) traps, which were not significantly different (P > 0.01) from an experimental moving-target trap that produced mean captures of 40 Ae. albopictus and 6 Ae. aegypti (alpha = 0.01). In terms of Ae. albopictus capture, no significant differences (P > 0.01) existed between Dragonfly, CDC without light (CDC -), and CDC with light (CDC +) captures, which were significantly different (P < 0.01) from Mosquito Deleto. No statistical significance existed between moving-target, omnidirectional, CDC +, CDC -, and Mosquito Deleto traps in terms of Ae. aegypti capture (P > 0.01), individual trap positions, or number of Ae. albopictus and Ae. aegypti females collected throughout the 21-day test (P > 0.05). Mosquito Magnet Liberty collected 7,208 Ae. albopictus, 1467 Ae. aegypti, and 13 other species representing 5 genera, which comprised the largest total (9662) and percentage (62.5%) of mosquitoes collected by all traps combined. Omnidirectional and moving-target traps captured 1941 and 1050 Ae. albopictus, 138 and 220 Ae. aegypti, and 2171 (14.0%) and 1397 (9.0%) of the total mosquitoes captured by all traps, with 8 and 10 species representing 5 genera, respectively, included in these collections. The Dragonfly captured 476 Ae. albopictus, 376 Ae. aegypti, and 1008 total specimens (6.5%) representing 8 species and 4 genera in these collections. CDC + and CDC - traps collected nearly identical numbers of Ae. albopictus (431, 450) and Ae. aegypti (71, 71) with 537 (3.4%) and 551 (3.5%) total specimens, respectively. Eight species representing 5 genera were captured from CDC +, whereas CDC - captured 6 species representing 4 genera. Mosquito Deleto captured 118 mosquitoes, including 19 Ae. albopictus and 62 Ae. aegypti females (0.7%), with 6 species representing 4 genera. Battery-powered traps with contrasting color schemes and movement worked considerably better than stationary CDC miniatures without color or movement. Omnidirectional Fay-Prince and moving-target traps without octenol captured Ae. albopictus and Ae. aegypti females as frequently as some commercial traps. Additionally, costs incurred per mosquito trapped, future trap design, and important consumer-centered issues are briefly discussed.     

主要气候因素变化影响2017-2018年广州蚊密度与登革流行趋势分析

目的 了解年度气候变化对广州蚊密度与登革流行趋势的影响。方法 2017年5月至2018年5月采用BG-Sentinel trap（BG-trap）在广州市校园、公园、小区三种不同生境开展蚊虫种群密度调查。采用广义估计方程(GEE)分析每月登革发病人数与温度、降雨量和白纹伊蚊密度的关系。结果 三种生境共捕获成蚊6853只，其中白纹伊蚊1028只，雌蚊534只。模型分析结果显示:月最高温度升高1℃，1个月后的登革发病数增加1.806倍；月降雨量每增加1mm，当月登革发病数减少0.012倍；每个BG-trap诱捕的白纹伊蚊雌蚊密度增加1只/天，当月登革发病数增加0.779倍。结论 广州市学校、公园、小区三种生境的蚊种种群构成有统计学差异，三种生境的白纹伊蚊每月密度变化和雌雄构成比均无统计学差异，但登革发病人数与前推一个月的最高温度和当月的白纹伊蚊雌蚊密度有正相关关系。     

西双版纳州登革热暴发现场BGS-trap媒介蚊虫监测研究

目的 评价BG-Sentinel mosquito trap （BGS-trap）对登革热媒介成蚊的监测效果,为我国登革热暴发现场伊蚊成蚊监测、风险评估及预测预警提供基础数据.方法 在西双版纳州所辖景洪市、勐腊及勐海县,利用BGS-Trap进行伊蚊成蚊监测,捕获蚊种经形态学鉴定.利用描述流行病学方法对日捕获所有蚊虫进行分析.结果 景洪市5d研究期内,共布放20台BGS-trap,累计捕蚊240 h,捕获蚊虫26只,其中,埃及伊蚊雌性1只,白纹伊蚊8只（雌7只,雄1只）,致倦库蚊17只（雌16只,雄1只）.勐腊、勐海县各放置BGS-trap 3台,捕蚊时间各108 h,均未捕到埃及伊蚊及白纹伊蚊.勐腊县捕获三带喙库蚊2只（雌雄各1只）,勐海县捕获致倦库蚊2只（雌雄各1只）.结论 BGS-trap在此次云南省西双版纳州登革热暴发现场伊蚊成蚊监测中效果不理想,需在现场和实验室对该装置进行进一步媒介伊蚊成蚊监测效果评价工作.     

北京市机场口岸蚊类及病原体携带情况调查分析

目的对北京市机场口岸蚊媒本底情况以及蚊媒病原体携带情况进行调查分析,评价北京市是否存在登革热和疟疾传播的蚊媒,为机场口岸蚊媒传播疾病预测预警提供依据。方法采用CO2灯诱法,对捕获的白纹伊蚊进行登革热病毒核酸检测和病毒分离,对中华按蚊进行4种疟原虫核酸检测。结果共捕获成蚊22 715只,密度指数为44.54只/(灯.h),淡色库蚊为优势种占87.95%;其次是三带喙库蚊,占10.64%;中华按蚊、白纹伊蚊分别占1.11%、0.30%。成蚊密度高峰期为8、9月。蚊媒疟原虫、登革热病原携带状况检测结果均为阴性。结论北京市机场口岸存在登革热和疟疾传播的蚊媒,北京市存在由输入性病例(境外感染病例及外省感染病例)引起登革热、疟疾本地传播的风险。应继续加强对机场口岸蚊媒密度监测以及蚊媒病原携带状况监测。     

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.     

First report of Aedes (Stegomyia) albopictus in the state of Ceará, Brazil

For the first time, the occurrence of Aedes (Stegomyia) albopictus in an urban area of the city of Fortaleza, Northeastern, Brazil, is reported. From January to July 2005, ovitraps were used to collect eggs from Aedes spp., which were kept under laboratory conditions to develop into the adult phase. The resultant mosquitoes were identified and subjected to dengue virus isolation tests. Thirteen specimens of Aedes albopictus, all females, were identified. No dengue virus was isolated in any of the mosquito pools. Even though Aedes albopictus has not been incriminated in Brazilian dengue outbreaks, the possibility of dengue virus transmission by these mosquitoes cannot be dismissed.     

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。     

Discovery of a widespread infestation of Aedes albopictus in the Torres Strait, Australia

Aedes albopictus is a container-breeding Stegomyia mosquito that has dispersed widely from its origins in Southeast Asia. Because Ae. albopictus is a known dengue vector and a potential vector of a variety of arboviruses and it can tolerate cooler climates than Aedes aegypti, Australian quarantine and health authorities have strategies to detect and eliminate it from international ports. Following the detection of 42 adult Ae. albopictus in BG-Sentinel traps set on Yorke island in the Torres Strait of Australia in April 2005, extensive surveys were conducted to determine the distribution of Ae. albopictus in the Torres Strait and adjoining Cape York Peninsula. A total of 17 islands and the northern peninsula area of Cape York Peninsula were surveyed by collection of larvae and pupae from flooded containers and human bait collections of adult mosquitoes with aspirators and sweep nets. Aedes albopictus was detected on 10 islands and comprised 100% of the day-biting container-breeding mosquitoes on Yorke and Stephens Islands. No Ae. albopictus were detected in the mainland sites on Cape York. Retrospective genetic analysis of larvae collected in April 2004 and April 2005 on Yorke Island indicated that Ae. albopictus was present in low densities in 2004 and that there were 3 genetically distinct mitochondrial haplotypes on Yorke Island in April 2005. Additionally, on Yorke Island there is evidence that Ae. albopictus is displacing Aedes scutellaris.     

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.     

The association of Aedes aegypti and Ae. albopictus in Allende, Nuevo León, Mexico

The recent appearance of Aedes Stegomyia albopictus (Skuse) in Nuevo León (NL) worries health officials. It is a vector of dengue fever in Asia and is more resistant to lower temperatures than Ae. aegypti. The objective of this study was to learn about some ecological parameters of Ae. albopictus and their association with Ae. aegypti, and other culicids in Allende, NL, Mexico, during 1999. Allende is a small town close to metropolitan Monterrey, which has 4 million inhabitants. The design was random with monthly sampling of 175 ovitraps. Chi-square analyses were performed with data of presence, absence, frequency, and relative abundances. During the study, the species Culex tarsalis (Coquillet), Cx. thriambus (Dyar), Cx. pipiens (Linnaeus), Cx. coronator (Dyar and Knab), Ae. albopictus, Ae. aegypti, Toxorhynchites rutilus (Coquillet), and Ae. triseriatus (Say) were found. April is the month for large numbers of mosquito species. September had the highest populations in positive ovitraps (66.67%), followed by July (63.27% of traps). Aedes aegypti was the most abundant (65.13%), followed by Ae. albopictus (19.71%). Both Ae. albopictus and Ae. aegypti were found from April until December. Aedes aegypti was more abundant than Ae. albopictus, except in August, when they were similar (chi2 = 0.197, P < 0.05). We found significant association between the presence of both species for every study month (chi2 = 9.837, P < 0.05), with a contingency coefficient of 0.247. September and November were the months having the most mosquitoes in this association. Only considering Ae. albopictus, more were found in ovitraps in July (34.6%), followed by September (33.3%). However, its presence was not significant throughout the year. Of 2 zones, in town and at the river, prevalence indicated that Ae. albopictus preferred the river. This mosquito is in its establishment phase in this area and requires further studies.     

Update on temporal and spatial abundance of dengue vectors in Penang, Malaysia

It is important to obtain frequent measurements of the abundance, distribution, and seasonality of mosquito vectors to determine the risk of disease transmission. The number of cases of dengue infection has increased in recent years on Penang Island, Malaysia, with recurring epidemics. However, ongoing control attempts are being critically hampered by the lack of up-to-date information regarding the vectors. To overcome this problem, we examined the current situation and distribution of dengue vectors on the island. Residences throughout the urban, suburban, and rural areas were inspected through wet and dry seasons between February 2009 and February 2010. Two vectors were encountered in the survey, with Aedes aegypti present in especially high numbers mostly in urban areas. Similar observations were noted for Ae. albopictus in rural areas. The former species was more abundant in outdoor containers, while the latter showed almost equivalent abundance both outdoors and indoors. The dengue virus was active in both urban and rural areas, and the number of cases of infection was higher in areas where Ae. aegypti was predominant. The abundance of immature Ae. albopictus was positively correlated with rainfall (r2 = 0.461; P < 0.05), but this was not the case for Ae. aegypti. For both species, the size of immature populations tended to increase with increasing intensity of rain, but heavy rains resulted in population loss. In addition to updating data regarding the larval habitats and locations (outdoors and indoors), this study highlighted the importance of spatial vector control stratification, which has the potential to reduce costs in control programs.     

Relative suitability of Aedes albopictus and Aedes aegypti in North Carolina to support development of Dirofilaria immitis

The relative suitability of two colonies established from local strains of Aedes albopictus (Wilmington and Rockingham) and a local (Raleigh) and laboratory (Liverpool) strain of Ae. aegypti to support development of Dirofilaria immitis was investigated. High levels of mortality occurred 1-2 days after mosquitoes fed on a heavily microfilaremic (28,617 microfilariae/ml) dog but not when mosquitoes were fed on a dog exhibiting a moderate microfilaremia (3,300 microfilariae/ml). At 15-16 days postfeeding, development of D. immitis to the third larval stage occurred to some extent in mosquitoes of all four strains. Microfilariae were only found in the Raleigh strain of Ae. aegypti. Aedes albopictus most frequently contained first and second stage larvae that were deteriorated which suggested that their development had been arrested. Third stage larvae were found most often in the Liverpool strain of Ae. aegypti. Colonies established from local strains of Ae. albopictus and Ae. aegypti do not appear to be suitable hosts of D. immitis.     

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.