Mboera Leonard E G, Mweya Clement N, Rumisha Susan F, Tungu Patrick K, Stanley Grades, Makange Mariam R, Misinzo Gerald, De Nardo Pasquale, Vairo Francesco, Oriyo Ndekya M
National Institute for Medical Research, Dar es Salaam, Tanzania.
Department of Veterinary Microbiology and Parasitology, Sokoine University of Agriculture, Morogoro, Tanzania.
PLoS Negl Trop Dis. 2016 Jan 26;10(1):e0004313. doi: 10.1371/journal.pntd.0004313. eCollection 2016 Jan.
In 2010, 2012, 2013 and 2014 dengue outbreaks have been reported in Dar es Salaam, Tanzania. However, there is no comprehensive data on the risk of transmission of dengue in the country. The objective of this study was to assess the risk of transmission of dengue in Dar es Salaam during the 2014 epidemic.
METHODOLOGY/PRINCIPAL FINDINGS: This cross-sectional study was conducted in Dar es Salaam, Tanzania during the dengue outbreak of 2014. The study involved Ilala, Kinondoni and Temeke districts. Adult mosquitoes were collected using carbon dioxide-propane powered Mosquito Magnet Liberty Plus traps. In each household compound, water-holding containers were examined for mosquito larvae and pupae. Dengue virus infection of mosquitoes was determined using real-time reverse transcription polymerase chain reaction (qRT-PCR). Partial amplification and sequencing of dengue virus genome in infected mosquitoes was performed. A total of 1,000 adult mosquitoes were collected. Over half (59.9%) of the adult mosquitoes were collected in Kinondoni. Aedes aegypti accounted for 17.2% of the mosquitoes of which 90.6% were from Kinondoni. Of a total of 796 houses inspected, 38.3% had water-holding containers in their premises. Kinondoni had the largest proportion of water-holding containers (57.7%), followed by Temeke (31.4%) and Ilala (23.4%). The most common breeding containers for the Aedes mosquitoes were discarded plastic containers and tires. High Aedes infestation indices were observed for all districts and sites, with a house index of 18.1% in Ilala, 25.5% in Temeke and 35.3% in Kinondoni. The respective container indices were 77.4%, 65.2% and 80.2%. Of the reared larvae and pupae, 5,250 adult mosquitoes emerged, of which 61.9% were Ae. aegypti. Overall, 27 (8.18) of the 330 pools of Ae. aegypti were positive for dengue virus. On average, the overall maximum likelihood estimate (MLE) indicates pooled infection rate of 8.49 per 1,000 mosquitoes (95%CI = 5.72-12.16). There was no significant difference in pooled infection rates between the districts. Dengue viruses in the tested mosquitoes clustered into serotype 2 cosmopolitan genotype.
CONCLUSIONS/SIGNIFICANCE: Ae. aegypti is the main vector of dengue in Dar es Salaam and breeds mainly in medium size plastic containers and tires. The Aedes house indices were high, indicating that the three districts were at high risk of dengue transmission. The 2014 dengue outbreak was caused by Dengue virus serotype 2. The high mosquito larval and pupal indices in the area require intensification of vector surveillance along with source reduction and health education.
2010年、2012年、2013年和2014年，坦桑尼亚达累斯萨拉姆均报告了登革热疫情。然而，该国尚无关于登革热传播风险的全面数据。本研究的目的是评估2014年疫情期间达累斯萨拉姆登革热的传播风险。
方法/主要发现：本横断面研究于2014年登革热疫情期间在坦桑尼亚达累斯萨拉姆开展。研究涉及伊拉拉、基农多尼和特梅克三个区。使用以二氧化碳-丙烷为动力的灭蚊磁体Liberty Plus诱捕器收集成年蚊子。在每个家庭院落中，检查储水容器以查找蚊虫幼虫和蛹。采用实时逆转录聚合酶链反应（qRT-PCR）检测蚊子的登革病毒感染情况。对受感染蚊子的登革病毒基因组进行部分扩增和测序。共收集到1000只成年蚊子。超过半数（59.9%）的成年蚊子是在基农多尼收集到的。埃及伊蚊占所捕蚊子的17.2%，其中90.6%来自基农多尼。在总共检查的796所房屋中，38.3%的房屋院落中有储水容器。基农多尼储水容器的比例最高（57.7%），其次是特梅克（31.4%）和伊拉拉（23.4%）。埃及伊蚊最常见的滋生容器是废弃塑料容器和轮胎。所有区和地点的埃及伊蚊侵扰指数都很高，伊拉拉的房屋指数为18.1%，特梅克为25.5%，基农多尼为35.3%。相应的容器指数分别为77.4%、65.2%和80.2%。饲养的幼虫和蛹羽化出5250只成年蚊子，其中61.9%为埃及伊蚊。总体而言，在330组埃及伊蚊中，有27组（8.18%）登革病毒呈阳性。平均而言，总体最大似然估计（MLE）表明每1000只蚊子的混合感染率为8.49（95%置信区间=5.72 - 12.16）。各区之间的混合感染率无显著差异。检测的蚊子中的登革病毒聚为血清型2全球基因型。
结论/意义：埃及伊蚊是达累斯萨拉姆登革热的主要传播媒介，主要在中型塑料容器和轮胎中滋生。埃及伊蚊房屋指数很高，表明这三个区登革热传播风险很高。2014年登革热疫情由登革病毒血清型2引起。该地区蚊虫幼虫和蛹指数较高，需要加强媒介监测，同时减少滋生源头并开展健康教育。
