Department of Disease Control, London School of Hygiene and Tropical Medicine, London, United Kingdom.
Institut Pierre Richet (IPR) / Institut National de Santé Publique (INSP), Bouaké, Côte d'Ivoire.
PLoS One. 2019 Apr 11;14(4):e0215074. doi: 10.1371/journal.pone.0215074. eCollection 2019.
There is evidence from experimental hut and household studies that the entomological efficacy of long lasting pyrethroid treated nets (LLINs) is compromised in areas of pyrethroid resistance. The rapid increase in resistance intensity in African malaria vectors could further undermine the performance of these nets. The pyrethroid resistance intensity in Anopheles gambiae s.l. M'bé from central Côte d'Ivoire is reported to be high (> 1700 fold). Whether this translates into an increase in entomological indicators of malaria transmission needs investigation.
The efficacy of two long lasting insecticidal nets (LN) MiraNet and MagNet, both alpha-cypermethrin based was evaluated in experimental huts against pyrethroid resistant Anopheles gambiae in M'bé, central Côte d'Ivoire. All nets were deliberately holed to simulate wear-and-tear and were tested unwashed and after 20 standardized washes.
The entry rates of An. gambiae s.l. into huts with insecticide treated nets were 62-84% lower than entry into huts with untreated nets (p < 0.001). Exit rates of An. gambiae s.l. with unwashed MiraNet and MagNet LNs were significantly greater than with untreated nets (50-60% vs 26%) and this effect after washing 20 times nets did not decrease. Blood-feeding with both nets was significantly inhibited relative to the untreated reference net (31-55%) (p < 0.001). Washing MiraNet LN 20 times had no significant impact on protection against An. gambiae s.l. bites but it did cause a significant fall by 40% in protection with MagNet LN (p < 0.001). All insecticide treated nets induced higher mortality of An. gambiae s.l. than the untreated net (p < 0.05). The impact though significant was limited (14-30%). The personal protection against An. gambiae s.l. bites derived from all treatments was high (75-90%). The overall insecticidal effect was compromised by pyrethroid resistance and was not detectable in some treatments.
In this area of high pyrethroid resistance intensity (over 1700 fold), both MiraNet and MagNet LNs still conferred appreciable personal protection against mosquito bites despite inducing only slightly greater mortality of pyrethroid resistant Anopheles mosquitoes than untreated nets. The impact is comparable to moderately intense Benin resistance area (207 fold) and Burkina Faso (over 1000 fold). This preserved level of protection plus the small but sensitive killing of mosquitoes may continue to impact vectorial capacity despite high intensity of resistance. Nevertheless, there is an obvious need for strategies and nets with novel mode of action to enhance vector control.
从实验棚屋和家庭研究中得出证据表明，在拟除虫菊酯抗性地区，长效拟除虫菊酯处理蚊帐（LLINs）的昆虫学功效受到了损害。非洲疟疾传播媒介中抗药性的迅速增强可能会进一步削弱这些蚊帐的性能。据报道，来自科特迪瓦中部的冈比亚按蚊复合体的拟除虫菊酯抗性强度很高（> 1700 倍）。这是否会转化为疟疾传播的昆虫学指标的增加仍需调查。
在科特迪瓦中部的 M'bé，评估了两种长效杀虫剂蚊帐（MiraNet 和 MagNet）对耐拟除虫菊酯的冈比亚按蚊的实验棚屋中的功效。所有蚊帐都故意穿孔以模拟磨损，并进行了未经清洗和经过 20 次标准化清洗的测试。
与未处理的蚊帐相比，进入有杀虫剂处理的蚊帐的冈比亚按蚊的进入率降低了 62-84%（p < 0.001）。未经清洗的 MiraNet 和 MagNet LN 的冈比亚按蚊的出口率明显高于未处理的蚊帐（50-60%对 26%），并且经过 20 次洗涤后这种效果并没有降低。与未处理的参考蚊帐相比，两种蚊帐的吸血均受到明显抑制（31-55%）（p < 0.001）。用 MiraNet LN 洗涤 20 次对保护冈比亚按蚊叮咬没有明显影响，但 MagNet LN 的保护作用下降了 40%（p < 0.001）。所有经杀虫剂处理的蚊帐引起的冈比亚按蚊死亡率均高于未处理的蚊帐（p < 0.05）。尽管影响是显著的，但它是有限的（14-30%）。所有治疗方法提供的个人对冈比亚按蚊叮咬的保护率均很高（75-90%）。由于拟除虫菊酯的抗性，整体杀虫效果受到损害，在某些处理中无法检测到。
在这种拟除虫菊酯抗性强度很高（超过 1700 倍）的地区，尽管 MiraNet 和 MagNet LN 对耐拟除虫菊酯的疟蚊的死亡率仅略高于未处理的蚊帐，但仍能提供可观的个人保护，免受蚊子叮咬。这种影响与贝宁中度抗性区（207 倍）和布基纳法索（超过 1000 倍）相当。尽管存在高强度的抗性，但这种保护水平的保留以及对蚊子的微小但敏感的杀伤，可能会继续影响媒介的传播能力。尽管如此，显然需要具有新作用模式的策略和蚊帐来增强蚊虫控制。
