National Institute of Health, Maputo, Mozambique.
PMI VectorWorks Project, Tropical Health LLP, Abuja, Nigeria.
Malar J. 2020 Jun 17;19(1):209. doi: 10.1186/s12936-020-03282-w.
Malaria prevention with long-lasting insecticidal nets (LLINs) has seen a tremendous scale-up in sub-Saharan Africa in the last decade. To sustain this success, it is important to understand how long LLINs remain in the households and continue to protect net users, which is termed durability. This information is needed to decide the appropriate timing of LLIN distribution and also to identify product(s) that may be underperforming relative to expectations. Following guidance from the U.S. President's Malaria Initiative, durability monitoring of polyethylene 150-denier LLIN (Royal Sentry and MAGNet) distributed during a 2017 mass campaign in Mozambique was implemented in three ecologically different sites: Inhambane, Tete, and Nampula.
This was a prospective cohort study in which representative samples of households from each district were recruited at baseline, 1 to 6 months after the mass campaign. All campaign LLINs in these households were labelled and followed up over a period of 36 months. The primary outcome was the "proportion of LLINs 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 subsamples of campaign LLINs.
A total of 998 households (98% of target) and 1998 campaign LLIN (85% of target) were included in the study. Definite outcomes could be determined for 80% of the cohort LLIN in Inhambane, 45% in Tete, and 72% in Nampula. The highest all-cause attrition was seen in Nampula with 74% followed by Inhambane at 56% and Tete at 50%. Overall, only 2% of campaign LLINs were used for other purposes. Estimated survival in serviceable condition of campaign LLINs after 36 months was 57% in Inhambane, 43% in Tete, and 33% in Nampula, corresponding to median survival of 3.0, 2.8, and 2.4 years, respectively. Factors that were associated with better survival were exposure to social and behavioural change communication, a positive net care attitude, and folding up the net during the day. Larger household size negatively impacted survival. Insecticidal performance was optimal up to 24 months follow-up, but declined at 36 months when only 3% of samples showed optimal effectiveness in Inhambane, 11% in Tete and 29% in Nampula. However, 96% of LLIN still had minimal effectiveness at 36 months.
Differences in median survival could be attributed at least in part to household environment and net care and repair behaviours. This means that in two of the three sites the assumption of a three-year cycle of campaign distributions holds, while in the Nampula site either continuous distribution channels could be expanded or more intense or targeted social and behaviour change activities to encourage net care and retention could be considered.
在过去十年中，长效驱虫蚊帐（LLINs）在撒哈拉以南非洲得到了极大的推广。为了保持这一成功，了解 LLINs 在家庭中持续多长时间并继续保护蚊帐使用者（称为耐用性）非常重要。这一信息对于决定适当的 LLIN 分发时间以及确定可能表现不如预期的产品（如果有的话）是必要的。根据美国总统疟疾倡议的指导，对莫桑比克 2017 年大规模运动期间分发的聚乙烯 150 旦尼尔 LLIN（Royal Sentry 和 MAGNet）的耐用性进行了监测，监测工作在三个生态环境不同的地点进行：伊尼扬巴内、太特和楠普拉。
这是一项前瞻性队列研究，在基线时、大规模运动后 1 至 6 个月，从每个地区的代表性家庭样本中招募参与者。这些家庭中的所有运动用 LLIN 都贴上标签，并在 36 个月的时间内进行跟踪。主要结局是根据损耗和完整性测量以及中位生存年限得出的“处于可用状态的 LLIN 比例”。通过对运动用 LLIN 的亚样本进行生物测定来确定杀虫耐用性的结果。
共有 998 户家庭（目标的 98%）和 1998 顶运动用 LLIN（目标的 85%）纳入了研究。在伊尼扬巴内，80%的队列 LLIN 可以确定明确的结局，在太特为 45%，在楠普拉为 72%。损耗率最高的是楠普拉，达到 74%，其次是伊尼扬巴内，为 56%，太特为 50%。总体而言，只有 2%的运动用 LLIN 用于其他用途。36 个月后，运动用 LLIN 处于可用状态的估计存活率在伊尼扬巴内为 57%，在太特为 43%，在楠普拉为 33%，对应的中位生存年限分别为 3.0 年、2.8 年和 2.4 年。与更好的生存相关的因素包括接触社会和行为改变沟通、对蚊帐护理的积极态度，以及白天将蚊帐收起。家庭规模较大对生存不利。杀虫性能在 24 个月的随访中最佳，但在 36 个月时下降，伊尼扬巴内只有 3%的样本显示最佳效果，太特为 11%，楠普拉为 29%。然而，在 36 个月时，96%的 LLIN 仍然具有最低的效果。
中位生存年限的差异至少部分归因于家庭环境和蚊帐护理和修复行为。这意味着，在这三个地点中的两个地点，运动分发的三年周期假设成立，而在楠普拉，要么可以扩大连续的分发渠道，要么可以加强社会和行为改变活动，以鼓励护理和保留蚊帐。
