Department of Parasitology, Faculty of Medicine, University of Kelaniya, Ragama, Sri Lanka; Deparment of Zoology, Faculty of Natural Sciences, Open University, Sri Lanka.
Department of Parasitology, Faculty of Medicine, University of Kelaniya, Ragama, Sri Lanka.
Parasitol Int. 2023 Feb;92:102686. doi: 10.1016/j.parint.2022.102686. Epub 2022 Sep 26.
Anopheles stephensi was first recorded in the coastal area of Mannar District, Sri Lanka, in December 2016. Since then, this vector has been isolated from other districts in the Northern and Eastern Provinces of Sri Lanka. Chemical control is the main arm of vector control that can be used to reduce the vector densities within a short period. Thus, the present study aimed at evaluating the efficacy of using selected insecticides for the control of An. stephensi larvae.
The third and fourth instar larval stages of An. stephensi (F2 generation) of field mosquitoes that were caught using cattle baited net trap collections from Columbuthurai, Kurunagar, and Navanthurai areas in Jaffna District, Sri Lanka, were obtained from the laboratory colony established at Jaffna. Batches of 100 larvae were taken for experiments and introduced separately to a concentration series of temephos and novaluron (0.04-400 ppm). A control test was also performed at each setup without introducing insecticides. The mortality rates of An. stephensi larvae exposed to different concentrations of larvicides were recorded at 1, 24 and 48-h intervals. The experiment was replicated five times at individual concentrations for each selected chemical. Data were analyzed using the General Linear Model (GLM) and Probit analysis.
The highest mortality rate (100%) at a 1-h exposure period was observed from temephos at >100 ppm. The mortality rates varied significantly for different concentrations and larvicides (p < 0.05). At 24-h of the exposure period, the 100% mortality of An. stephensi larvae were observed from both temephos and novaluron even at 0.04 ppm.
Both temephos and novaluron reported 100% mortality rates in An. stephensi larvae at 1-h and 24-h exposure periods. Based on the findings, temephos and novaluron can be recommended as effective larvicides for chemical-based control of An. stephensi in Jaffna, Sri Lanka. Further, it is recommended to conduct a field-based study, where habitat types and water quality are highly heterogeneous and may affect the residual activity.
2016 年 12 月，斯里兰卡马纳尔区沿海首次发现疟蚊斯氏亚种。此后，该媒介在斯里兰卡北部和东部的其他地区也有分离。化学控制是控制蚊虫密度的主要手段，可以在短时间内降低蚊虫密度。因此，本研究旨在评估使用选定杀虫剂控制疟蚊斯氏亚种幼虫的效果。
从斯里兰卡贾夫纳区科伦布图赖、库伦加和纳文塔鲁雷地区使用牛诱捕网收集的田间蚊子中获得第三和第四龄期幼虫（F2 代），并从贾夫纳建立的实验室蚊群中获得。取 100 条幼虫进行实验，分别引入噻虫嗪和双氧威（0.04-400 ppm）的浓度系列。在每个设置中也进行了对照试验，没有引入杀虫剂。在 1、24 和 48 小时间隔记录暴露于不同浓度杀幼虫剂的疟蚊斯氏亚种幼虫的死亡率。在每个选定化学物质的个体浓度下重复进行五次实验。使用一般线性模型（GLM）和概率分析对数据进行分析。
在 1 小时暴露期，噻虫嗪浓度>100 ppm 时死亡率最高（100%）。不同浓度和杀幼虫剂的死亡率差异显著（p <0.05）。在暴露 24 小时后，即使在 0.04 ppm 时，噻虫嗪和双氧威也能使疟蚊斯氏亚种幼虫 100%死亡。
噻虫嗪和双氧威在 1 小时和 24 小时暴露期对疟蚊斯氏亚种幼虫的死亡率均为 100%。根据研究结果，噻虫嗪和双氧威可推荐为在斯里兰卡贾夫纳地区进行基于化学的疟蚊斯氏亚种控制的有效杀幼虫剂。此外，建议进行实地研究，因为栖息地类型和水质高度异质，可能会影响残留活性。
