Howard Annabel F V, Adongo Elizabeth A, Hassanali Ahmed, Omlin Francois X, Wanjoya Anthony, Zhou Guofa, Vulule John
International Centre of Insect Physiology and Ecology (icipe), PO Box 30772-00100, Nairobi, Kenya.
J Med Entomol. 2009 Jan;46(1):107-14. doi: 10.1603/033.046.0114.
Azadirachta indica A. Juss (the neem tree), a source of limonoid insect growth regulatory (IGRs), grows well in many places in sub-Saharan Africa. We explored the potential of neem wood and bark chippings in malaria vector control by evaluating their aqueous extracts as a larvicide and growth disruptor of Anopheles gambiae s.s. (Diptera: Culicidae) under laboratory conditions. Immature stages of the mosquito were tested using WHO guidelines. Fifty percent inhibition of adult emergence (IE50) of all larval instars was obtained with <0.4 g of neem chippings in 1 liter of distilled water. For pupae, significant mortality occurred at 5 g/liter. Inhibition of pupation was seen with some larvae staying as LIVs for 9 d before dying. In addition to growth retardation, reduced reaction by larvae to visual and mechanical stimuli observed at higher neem concentrations may make them more susceptible to natural predators. There were no significant differences in the sex ratio of emerged adults or wing length of females compared with the controls. High-performance liquid chromatography of aqueous extracts showed a series of constituents of varying polarity, including the limonoids nimbin and salannin, which were quantified. Azadirachtin was not detected and the observed activities are attributed to other constituents of the chippings. Such larvicides can be particularly effective where larval habitats are relatively large and readily identifiable. Aqueous extracts of neem wood chippings can be produced locally and their use has the potential to be a low-tech component of integrated malaria vector control schemes in sub-Saharan Africa.
印楝（Azadirachta indica A. Juss）是一种柠檬苦素类昆虫生长调节剂的来源，在撒哈拉以南非洲的许多地方都生长良好。我们通过在实验室条件下评估印楝木片和树皮碎片的水提取物作为冈比亚按蚊（双翅目：蚊科）的杀幼虫剂和生长干扰剂，来探索其在疟疾媒介控制中的潜力。按照世界卫生组织的指南对蚊子的未成熟阶段进行了测试。在1升蒸馏水中加入<0.4克印楝碎片，所有幼虫龄期的成虫羽化抑制率达到50%（IE50）。对于蛹，在浓度为5克/升时出现显著死亡率。观察到一些幼虫出现化蛹抑制，它们以低龄幼虫状态存活9天后死亡。除了生长迟缓外，在较高印楝浓度下观察到幼虫对视觉和机械刺激的反应降低，这可能使它们更容易受到自然捕食者的攻击。与对照组相比，羽化成虫的性别比例或雌虫翅长没有显著差异。水提取物的高效液相色谱分析显示了一系列不同极性的成分，包括柠檬苦素类化合物印楝素和萨兰宁，并对其进行了定量。未检测到印楝素，观察到的活性归因于碎片中的其他成分。这种杀幼虫剂在幼虫栖息地相对较大且易于识别的地方可能特别有效。印楝木片的水提取物可以在当地生产，其使用有可能成为撒哈拉以南非洲综合疟疾媒介控制方案的一项低技术组成部分。
