KEMRI/CDC Research and Public Health Collaboration, PO Box 1578, Kisumu 40100, Kenya.
Malar J. 2013 Oct 24;12:368. doi: 10.1186/1475-2875-12-368.
Long-lasting insecticide-treated mosquito nets (LLINs) are a primary malaria prevention strategy in sub-Saharan Africa. However, emergence of insecticide resistance threatens the effectiveness of LLINs.
Cross-sectional surveys of LLINs were conducted in houses of seven and four villages in Gem and Bungoma Districts in western Kenya, respectively. Condition (number and area of holes in the nets), number and species of mosquitoes resting inside them, and insecticidal activity of nets were quantified. Mosquitoes collected inside nets were allowed to lay eggs and progeny tested for susceptibility to deltamethrin and permethrin, pyrethoids commonly deployed in LLINs in western Kenya.
In Gem, 83.3% of nets were less than three years old and 32.4% had at least one hole of any size; while in Bungoma, 92% were less than three years old and 48% had at least one hole. No anopheline and five Culex spp. mosquitoes were found resting inside nets in Gem regardless of the number and size of holes, while 552 Anopheles gambiae s.l., five Anopheles funestus s.l. and 137 Culex spp. were in nets in Bungoma. The number of mosquitoes resting inside nets increased with hole areas >50 cm in Bungoma. In WHO resistance assays, f1 offspring of samples collected in nets in Bungoma were 94 and 65% resistant to deltamethrin and permethrin, respectively. Nets from Bungoma retained strong activity against a susceptible laboratory strain, but not against f1 offspring of field-collected An. gambiae s.s. All An. gambiae s.s. samples collected in nets were homozygous for the kdr genotype L1014S.
In areas with pyrethroid resistant vectors, LLINs with modest hole areas permit mosquito entry and feeding, providing little protection against the vectors. LLIN formulations develop large holes within three years of use, diminishing their presupposed lifetime effectiveness.
长效驱虫蚊帐（LLINs）是撒哈拉以南非洲地区预防疟疾的主要策略。然而，杀虫剂抗性的出现威胁到 LLINs 的有效性。
在肯尼亚西部的 Gem 和 Bungoma 区的七个和四个村庄的房屋中进行了 LLIN 的横断面调查。定量了蚊帐的状况（网中的孔的数量和面积）、里面栖息的蚊子数量和种类，以及蚊帐的杀虫活性。允许在蚊帐内收集的蚊子产卵，并对其后代进行对溴氰菊酯和氯菊酯（在肯尼亚西部常用的两种拟除虫菊酯）的敏感性测试。
在 Gem，83.3%的蚊帐不到三年，32.4%有至少一个大小的孔；而在 Bungoma，92%的蚊帐不到三年，48%有至少一个孔。在 Gem，无论孔的数量和大小如何，都没有发现疟蚊和五种库蚊在蚊帐内栖息，而在 Bungoma，有 552 只冈比亚按蚊 s.l.、五种致倦库蚊 s.l.和 137 只库蚊在蚊帐内。在 Bungoma，随着孔面积大于 50cm，栖息在蚊帐内的蚊子数量增加。在世界卫生组织的抗药性测定中，从 Bungoma 蚊帐中采集的样本的 f1 后代对溴氰菊酯和氯菊酯的抗性分别为 94%和 65%。来自 Bungoma 的蚊帐对敏感实验室株仍保持强烈的活性，但对从野外采集的 An. gambiae s.s. 的 f1 后代无效。从蚊帐中采集的所有 An. gambiae s.s.样本均为 kdr 基因型 L1014S 的纯合子。
在有拟除虫菊酯抗性媒介的地区，具有适度孔面积的 LLINs 允许蚊子进入和进食，对媒介的保护作用很小。LLINs 在使用三年后形成大洞，从而降低了它们预期的使用寿命。
