Eastern & Southern Africa Centre of International Parasite Control, Kenya Medical Research Institute, Nairobi, Kenya.
School of Health Sciences, Meru University of Science and Technology, Meru, Kenya.
Infect Dis Poverty. 2021 Dec 20;10(1):135. doi: 10.1186/s40249-021-00916-2.
Long-lasting insecticide nets (LLINs) are a core malaria intervention. LLINs should retain efficacy against mosquito vectors for a minimum of three years. Efficacy and durability of Olyset Plus, a permethrin and piperonyl butoxide (PBO) treated LLIN, was evaluated versus permethrin treated Olyset Net. In the absence of WHO guidelines of how to evaluate PBO nets, and considering the manufacturer's product claim, Olyset Plus was evaluated as a pyrethroid LLIN.
This was a household randomized controlled trial in a malaria endemic rice cultivation zone of Kirinyaga County, Kenya between 2014 and 2017. Cone bioassays and tunnel tests were done against Anopheles gambiae Kisumu. The chemical content, fabric integrity and LLIN survivorship were monitored. Comparisons between nets were tested for significance using the Chi-square test. Exact binomial distribution with 95% confidence intervals (95% CI) was used for percentages. The WHO efficacy criteria used were ≥ 95% knockdown and/or ≥ 80% mortality rate in cone bioassays and ≥ 80% mortality and/or ≥ 90% blood-feeding inhibition in tunnel tests.
At 36 months, Olyset Plus lost 52% permethrin and 87% PBO content; Olyset Net lost 24% permethrin. Over 80% of Olyset Plus and Olyset Net passed the WHO efficacy criteria for LLINs up to 18 and 12 months, respectively. At month 36, 91.2% Olyset Plus and 86.4% Olyset Net survived, while 72% and 63% developed at least one hole. The proportionate Hole Index (pHI) values representing nets in good, serviceable and torn condition were 49.6%, 27.1% and 23.2%, respectively for Olyset Plus, and 44.9%, 32.8% and 22.2%, respectively for Olyset Net but were not significantly different.
Olyset Plus retained efficacy above or close to the WHO efficacy criteria for about 2 years than Olyset Net (1-1.5 years). Both nets did not meet the 3-year WHO efficacy criteria, and showed little attrition, comparable physical durability and survivorship, with 50% of Olyset Plus having good and serviceable condition after 3 years. Better community education on appropriate use and upkeep of LLINs is essential to ensure effectiveness of LLIN based malaria interventions.
长效杀虫剂蚊帐（LLINs）是疟疾的核心干预措施。LLINs 应至少保持三年的杀虫效力。本研究评估了拟除虫菊酯和增效醚（PBO）处理的 Olyset Plus 长效杀虫剂蚊帐相对于拟除虫菊酯处理的 Olyset Net 的功效和耐用性。由于缺乏世卫组织关于如何评估 PBO 蚊帐的指导方针，并且考虑到制造商的产品宣称，Olyset Plus 被评估为一种拟除虫菊酯 LLIN。
这是一项在肯尼亚 Kirinyaga 县疟疾流行的水稻种植区于 2014 年至 2017 年期间进行的家庭随机对照试验。针对冈比亚按蚊进行了锥形生物测定和隧道试验。监测了杀虫剂含量、织物完整性和 LLIN 存活率。使用卡方检验测试了蚊帐之间的差异。使用 95%置信区间（95%CI）的精确二项式分布表示百分比。锥形生物测定的世卫组织功效标准为≥95%击倒率和/或≥80%死亡率，隧道试验为≥80%死亡率和/或≥90%的血液摄取抑制率。
36 个月时，Olyset Plus 失去了 52%的拟除虫菊酯和 87%的增效醚含量；Olyset Net 失去了 24%的拟除虫菊酯。在 18 个月和 12 个月时，Olyset Plus 和 Olyset Net 分别有超过 80%的符合世卫组织对 LLIN 功效标准。36 个月时，91.2%的 Olyset Plus 和 86.4%的 Olyset Net 存活，而 72%和 63%的蚊帐出现至少一个孔。分别代表良好、可用和破损状态的比例孔指数（pHI）值分别为 Olyset Plus 的 49.6%、27.1%和 23.2%，Olyset Net 的 44.9%、32.8%和 22.2%，但差异无统计学意义。
Olyset Plus 在 2 年左右的时间内保持了高于或接近世卫组织功效标准的功效，而 Olyset Net（1-1.5 年）。两种蚊帐均未达到世卫组织 3 年功效标准，但在物理耐久性和存活率方面表现出较小的损耗，在 3 年后，50%的 Olyset Plus 处于良好和可用状态。需要对社区进行有关适当使用和维护 LLIN 的更好教育，以确保基于 LLIN 的疟疾干预措施的有效性。
