London School of Hygiene and Tropical Medicine (LSHTM), London, WC1E 7HT, UK.
Centre de Recherches Entomologiques de Cotonou (CREC), Cotonou, Benin.
Parasit Vectors. 2024 Oct 7;17(1):420. doi: 10.1186/s13071-024-06504-1.
Studies evaluating the attrition, physical and insecticidal durability of dual active ingredient (AI) insecticide-treated nets (ITNs) are essential for making programmatic decisions regarding their deployment. We performed a prospective study embedded in a cluster randomised controlled trial (cRCT) to evaluate the attrition, fabric integrity and insecticidal durability of Interceptor® G2 (alpha-cypermethrin-chlorfenapyr) and Royal Guard® (alpha-cypermethrin-pyriproxyfen), compared to Interceptor® (alpha-cypermethrin) in Benin.
A total of 2428 study nets in 1093 randomly selected households in five clusters per arm of the cRCT were monitored for ITN attrition and fabric integrity every 6-12 months post-distribution. Householders were further surveyed to investigate non-study net use and their preference for ITN fabric types used in the study nets. A second cohort of 120 nets per ITN type were withdrawn every 12 months and assessed for chemical content and insecticidal activity in laboratory bioassays. Alpha-cypermethrin bioefficacy was investigated using the susceptible Anopheles gambiae Kisumu strain, and chlorfenapyr and pyriproxyfen bioefficacy were investigated using the pyrethroid-resistant Anopheles coluzzii Akron strain. Net pieces were tested in WHO cone bioassays and tunnel tests for alpha-cypermethrin and in tunnel tests for chlorfenapyr; pyriproxyfen activity was assessed in cone bioassays as the reduction in fertility of blood-fed survivors using ovary dissection. Bioefficacy was expressed as the proportion of ITNs passing predetermined WHO criteria, namely knock-down ≥ 95% or 24/72 h mortality ≥ 80% or reduction in fertility ≥ 50%.
Overall ITN survivorship was 52% at 24 months and fell to 15% at 36 months. Median ITN survival time was lower with Royal Guard® relative to Interceptor® [1.6 vs 2.3 years; hazard ratio (HR) 1.49, 95% confidence interval (CI) 1.36-1.66; p < 0.001] and Interceptor® G2 (1.6 vs 2.1 years; HR 1.33, 95% CI 1.20-1.47; p < 0.001). Householders overwhelmingly preferred polyester nets over polyethylene nets (96%), and more Royal Guard® nets were replaced with spare polyester nets from previous campaigns. All Royal Guard® nets passed efficacy criteria for alpha-cypermethrin at all time points (100%) while ITN pass rates after 24 months had fallen to < 40% for pyriproxyfen and chlorfenapyr. The chemical content analysis showed a higher loss rate of the non-pyrethroid insecticides relative to the pyrethroids in each dual ingredient AI ITN; 74% vs 47% for Royal Guard® and 85% vs 63% for Interceptor® G2 at 36 months.
The median ITN survival time for Interceptor® G2 (2.1 years) and Royal Guard® (1.6 years) in Benin is substantially lower than 3 years. Royal Guard® nets were discarded more quickly by householders, partly due to their low preference for polyethylene nets. The insecticidal activity of the non-pyrethroid insecticides in both dual AI ITNs was short-lived compared to alpha-cypermethrin. The results corroborate the findings from the cRCT conducted in Benin.
评估双活性成分（AI）杀虫剂处理蚊帐（ITN）的损耗、物理和杀虫耐久性对于做出关于其部署的方案决策至关重要。我们在一项前瞻性研究中嵌入了一项集群随机对照试验（cRCT），以评估Interceptor® G2（alpha-氯菊酯-氯芬虫酯）和Royal Guard®（alpha-氯菊酯-吡丙醚）与贝宁的Interceptor®（alpha-氯菊酯）相比的损耗、织物完整性和杀虫耐久性。
在该 cRCT 的每个臂的五个集群中，总共监测了 2428 顶研究用蚊帐，每 6-12 个月监测一次 ITN 的损耗和织物完整性。户主还接受了调查，以调查非研究用网的使用情况以及他们对研究用网中使用的 ITN 织物类型的偏好。每 12 个月从每种 ITN 类型中撤出一个 120 顶的第二组蚊帐，并在实验室生物测定中评估其化学含量和杀虫活性。使用敏感的冈比亚按蚊 Kisumu 株调查 alpha-氯菊酯的生物效能，使用对拟除虫菊酯具有抗性的阿克拉按蚊 Anopheles coluzzii 株调查氯芬虫酯和吡丙醚的生物效能。用 WHO 锥形生物测定和隧道试验测试网片的 alpha-氯菊酯，用隧道试验测试氯芬虫酯；吡丙醚的活性通过对血餐幸存者进行卵巢解剖来评估减少生育能力来评估。生物效能表示为符合预定的 WHO 标准的 ITN 的比例，即击倒率≥95%或 24/72 小时死亡率≥80%或生育能力降低≥50%。
总体而言，ITN 的存活率在 24 个月时为 52%，在 36 个月时降至 15%。与 Interceptor®相比，Royal Guard®的中位 ITN 存活时间更短[1.6 年与 2.3 年；危险比（HR）1.49，95%置信区间（CI）1.36-1.66；p<0.001]和 Interceptor® G2（1.6 年与 2.1 年；HR 1.33，95% CI 1.20-1.47；p<0.001）。户主非常喜欢聚酯网而不是聚乙烯网（96%），而且更多的 Royal Guard®网被以前活动中的备用聚酯网所取代。所有 Royal Guard®网在所有时间点都通过了 alpha-氯菊酯的疗效标准（100%），而经过 24 个月后，吡丙醚和氯芬虫酯的 ITN 通过率已降至<40%。化学含量分析表明，与每种双成分 AI ITN 中的拟除虫菊酯相比，非拟除虫菊酯类杀虫剂的损失率更高；36 个月时，Royal Guard®为 74%，Interceptor® G2 为 85%。
Interceptor® G2（2.1 年）和 Royal Guard®（1.6 年）在贝宁的中位 ITN 存活时间大大低于 3 年。户主更快地丢弃了 Royal Guard®网，部分原因是他们对聚乙烯网的偏好较低。与 alpha-氯菊酯相比，两种双 AI ITN 中的非拟除虫菊酯类杀虫剂的杀虫活性持续时间较短。结果与在贝宁进行的 cRCT 结果相符。
