Zanzibar Malaria Elimination Programme, Stone Town, Zanzibar, Tanzania.
PMI VectorWorks Project, Tropical Health LLP, Abuja, Nigeria.
Malar J. 2020 May 24;19(1):187. doi: 10.1186/s12936-020-03258-w.
Malaria transmission in Zanzibar has dramatically reduced in recent years but vector control interventions such as long-lasting insecticidal nets (LLIN) must continue to reach malaria elimination. To achieve this, the Zanzibar Malaria Elimination Programme needs actionable evidence of the durability of the LLIN brands distributed. This study compared physical and insecticidal durability of two LLIN brands: Olyset and PermaNet© 2.0 in two similar districts on the islands of Unguja and Pemba.
This was a prospective cohort study of representative samples of households from two districts, recruited at baseline 4 months after the mass campaign. All campaign nets in these households were labelled and followed up over a period of 33 months. Primary outcome was the "proportion of nets surviving in serviceable condition" based on attrition and integrity measures and the median survival in years. The outcome for insecticidal durability was determined by bio-assay from sub-samples of campaign nets.
A total of 834 campaign nets (121% of target) from 299 households were included in the study. Definite outcomes could be determined for 86% of the cohort nets in Unguja (PermaNet 2.0) and 89% in Pemba (Olyset). After 33 months, physical survival in serviceable condition was 55% in Unguja and 51% in Pemba. Estimated median survival was lower in Pemba at all time points with 2.3-2.7 years compared to 3.1-3.3 yeas in Unguja. Multivariable Cox proportionate hazard models confirmed the difference between brands (p < 0.0001) and identified household net-care attitude (p = 0.007) and folding of hanging nets during the day (p < 0.0001) as significant determinants, in addition to exclusive use of nets by adults (p = 0.03) and use only over a finished bedframe (p = 0.01). Optimal insecticidal effectiveness was 80% or higher for both brands at all time points when both cone bio-assays and tunnel tests were applied.
After 3 years of follow-up, Olyset LLIN showed significantly lower physical survival compared to PermaNet 2.0 LLIN even after adjusting for other variables of net-use environment and net handling. This suggests that the differences were driven by the textile characteristics of the LLIN brands.
近年来，桑给巴尔的疟疾传播情况已大幅减少，但长效驱虫蚊帐（LLIN）等病媒控制干预措施必须继续实施，以实现消除疟疾的目标。为实现这一目标，桑给巴尔消除疟疾规划需要掌握分发的 LLIN 品牌耐用性的实际证据。本研究比较了两种 LLIN 品牌——Olyset 和 PermaNet©2.0 在桑给巴尔岛 Unguja 和 Pemba 两个类似地区的物理和杀虫耐用性。
这是一项前瞻性队列研究，从两个地区的代表性家庭样本中招募，在大规模运动后 4 个月进行基线调查。这些家庭中的所有运动蚊帐都贴上标签，并在 33 个月的时间内进行随访。主要结局指标是根据损耗和完整性测量以及中位数生存年限得出的“仍处于可用状态的蚊帐比例”。杀虫耐用性的结果通过从运动蚊帐的亚样本中进行生物测定来确定。
共有 299 户家庭的 834 顶运动蚊帐（占目标的 121%）纳入研究。Unguja（PermaNet 2.0）的队列蚊帐中有 86%，Pemba（Olyset）中有 89%的蚊帐可以确定明确的结局。33 个月后，Unguja 处于可用状态的蚊帐物理存活率为 55%，Pemba 为 51%。在所有时间点，Pemba 的估计中位生存年限均较低，为 2.3-2.7 年，而 Unguja 为 3.1-3.3 年。多变量 Cox 比例风险模型证实了品牌之间的差异（p<0.0001），并确定了家庭蚊帐护理态度（p=0.007）和白天悬挂蚊帐时的折叠方式（p<0.0001），以及成人专用（p=0.03）和仅在成品床架上使用（p=0.01）是重要的决定因素。当同时应用锥形生物测定和隧道试验时，两种品牌在所有时间点的最佳杀虫效果均为 80%或更高。
在 3 年的随访后，即使在调整了其他环境和处理因素后，与 PermaNet 2.0 LLIN 相比，Olyset LLIN 的物理存活情况明显更低。这表明差异是由 LLIN 品牌的纺织特性驱动的。
