Mathias Leah, Baraka Vito, Philbert Anitha, Innocent Ester, Francis Filbert, Nkwengulila Gamba, Kweka Eliningaya J
Department of Zoology and Wildlife Conservation, College of Natural and Applied Sciences, University of Dar es Salaam, P.O. Box 35165, Dar es Salaam, Tanzania.
National Institute for Medical Research, Tanga Medical Research Centre, P.O. Box 5004, Tanga Urban, Tanga, Tanzania.
Infect Dis Poverty. 2017 Jun 9;6(1):102. doi: 10.1186/s40249-017-0316-0.
Aedes aegypti (Diptera: Culicidae) is the main vector of the dengue virus globally. Dengue vector control is mainly based on reducing the vector population through interventions, which target potential breeding sites. However, in Tanzania, little is known about this vector's habitat productivity and insecticide susceptibility status to support evidence-based implementation of control measures. The present study aimed at assessing the productivity and susceptibility status of A. aegypti mosquitoes to pyrethroid-based insecticides in Dar es Salaam, Tanzania.
An entomological assessment was conducted between January and July 2015 in six randomly selected wards in Dar es Salaam, Tanzania. Habitat productivity was determined by the number of female adult A. aegypti mosquitoes emerged per square metre. The susceptibility status of adult A. aegypti females after exposure to 0.05% deltamethrin, 0.75% permethrin and 0.05% lambda-cyhalothrin was evaluated using the standard WHO protocols. Mortality rates were recorded after 24 h exposure and the knockdown effect was recorded at the time points of 10, 15, 20, 30, 40, 50 and 60 min to calculate the median knockdown times (KDT and KDT).
The results suggest that disposed tyres had the highest productivity, while water storage tanks had the lowest productivity among the breeding habitats Of A. aegypti mosquitoes. All sites demonstrated reduced susceptibility to deltamethrin (0.05%) within 24 h post exposure, with mortalities ranging from 86.3 ± 1.9 (mean ± SD) to 96.8 ± 0.9 (mean ± SD). The lowest and highest susceptibilities were recorded in Mikocheni and Sinza wards, respectively. Similarly, all sites demonstrated reduced susceptibility permethrin (0.75%) ranging from 83.1 ± 2.1% (mean ± SD) to 96.2 ± 0.9% (mean ± SD), in Kipawa and Sinza, respectively. Relatively low mortality rates were observed in relation to lambda-cyhalothrin (0.05%) at all sites, ranging from 83.1 ± 0.7 (mean ± SD) to 86.3 ± 1.4 (mean ± SD). The median KDT for deltamethrin, permethrin and lambda-cyhalothrin were 24.9-30.3 min, 24.3-34.4 min and 26.7-32.8 min, respectively. The KDT were 55.2-90.9 min for deltamethrin, 54.3-94.6 min for permethrin and 64.5-69.2 min for lambda-cyhalothrin.
The productive habitats for A. aegypti mosquitoes found in Dar es Salaam were water storage containers, discarded tins and tyres. There was a reduced susceptibility of A. aegypti to and emergence of resistance against pyrethroid-based insecticides. The documented differences in the resistance profiles of A. aegypti mosquitoes warrants regular monitoring the pattern concerning resistance against pyrethroid-based insecticides and define dengue vector control strategies.
埃及伊蚊（双翅目：蚊科）是全球登革热病毒的主要传播媒介。登革热媒介控制主要基于通过干预措施减少媒介种群数量，这些措施针对潜在的繁殖场所。然而，在坦桑尼亚，对于这种媒介的栖息地生产力以及对杀虫剂的敏感性状况了解甚少，难以支持基于证据的控制措施实施。本研究旨在评估坦桑尼亚达累斯萨拉姆市埃及伊蚊的生产力以及对拟除虫菊酯类杀虫剂的敏感性状况。
2015年1月至7月在坦桑尼亚达累斯萨拉姆市随机选择的6个街区进行了昆虫学评估。栖息地生产力通过每平方米羽化出的成年雌性埃及伊蚊数量来确定。成年雌性埃及伊蚊暴露于0.05%溴氰菊酯、0.75%氯菊酯和0.05%高效氯氟氰菊酯后，使用世界卫生组织标准方案评估其敏感性状况。暴露24小时后记录死亡率，并在10、15、20、30、40、50和60分钟时间点记录击倒效应，以计算中位击倒时间（KDT和KDT）。
结果表明，在埃及伊蚊的繁殖栖息地中，废弃轮胎的生产力最高，而储水箱的生产力最低。所有地点在暴露后24小时内对溴氰菊酯（0.05%）的敏感性均降低，死亡率范围为86.3±1.9（平均值±标准差）至96.8±0.9（平均值±标准差）。最低和最高敏感性分别记录在米科切尼和辛扎街区。同样，所有地点对氯菊酯（0.75%）的敏感性均降低，分别在基帕瓦和辛扎街区，范围为83.1±2.1%（平均值±标准差）至96.2±0.9%（平均值±标准差）。在所有地点，与高效氯氟氰菊酯（0.05%）相关的死亡率相对较低，范围为83.1±0.7（平均值±标准差）至86.3±1.4（平均值±标准差）。溴氰菊酯、氯菊酯和高效氯氟氰菊酯的中位KDT分别为24.9 - 30.3分钟、24.3 - 34.4分钟和26.7 - 32.8分钟。溴氰菊酯的KDT为55.2 - 90.9分钟，氯菊酯的KDT为54.3 - 94.6分钟，高效氯氟氰菊酯的KDT为64.5 - 69.2分钟。
在达累斯萨拉姆市发现的埃及伊蚊的繁殖栖息地为储水容器、废弃锡罐和轮胎。埃及伊蚊对拟除虫菊酯类杀虫剂的敏感性降低且出现了抗性。记录的埃及伊蚊抗性特征差异需要定期监测其对拟除虫菊酯类杀虫剂的抗性模式，并确定登革热媒介控制策略。
