Centre for Applied Malaria Research and Evaluation, Tulane School of Public Health and Tropical Medicine, 1440 Canal Street, New Orleans, LA, 70112, USA.
PATH, Kaoma, Zambia.
Parasit Vectors. 2024 Oct 14;17(1):429. doi: 10.1186/s13071-024-06457-5.
Some settings continue to experience a high malaria burden despite scale-up of malaria vector control to high levels of coverage. Characterisation of persistent malaria transmission in the presence of standard control measures, also termed residual malaria transmission, to understand where and when individuals are exposed to vector biting is critical to inform refinement of prevention and control strategies.
Secondary analysis was performed using data collected during a phase III cluster randomized trial of attractive targeted sugar bait stations in Western Province, Zambia. Two seasonal cohorts of children aged 1-14 years were recruited and monitored monthly during the malaria transmission season, concurrent with entomological surveillance using a combination of human landing catch (HLC) and Centres for Disease Control (CDC) light traps at randomly selected households in study clusters. Behavioural data from cohort participants were combined with measured Anopheles funestus landing rates and sporozoite positivity to estimate the human behaviour-adjusted entomological inoculation rate (EIR).
Behavioural data from 1237 children over 5456 child-visits in 20 entomology surveillance clusters were linked with hourly landing rates from 8131 female An. funestus trapped by HLC. Among all An. funestus tested by enzyme-linked immunosorbent assay (ELISA), 3.3% were sporozoite-positive. Mean EIR directly measured from HLC was 0.07 infectious bites per person per night (ib/p/n). When accounting for child locations over the evening and night, the mean behaviour-adjusted EIR was 0.02 ib/p/n. Children not sleeping under insecticide-treated nets (ITNs) experienced 13.6 infectious bites per person per 6 month season, 8% of which occurred outdoors, while ITN users received 1.3 infectious bites per person per 6 month season, 86% of which were received outdoors. Sleeping under an ITN can prevent approximately 90% of potential An. funestus bites among children.
In this setting ITNs have a high personal protective efficacy owing to peak An. funestus biting occurring indoors while most individuals are asleep. However, despite high household possession of ITNs (>90%) and high individual use (>70%), children in this setting experience more than one infectious bite per person per 6 month transmission season, sufficient to maintain high malaria transmission and burden. New tools and strategies are required to reduce the malaria burden in such settings.
尽管疟疾媒介控制已大规模扩展到较高覆盖率，但在一些环境中疟疾负担仍然很高。在标准控制措施存在的情况下，对持续存在的疟疾传播进行特征描述，也称为残留疟疾传播，以了解个体何时何地受到蚊虫叮咬，这对于完善预防和控制策略至关重要。
本研究采用赞比亚西部一项三阶段集群随机试验中收集的数据进行二次分析。试验招募了年龄在 1-14 岁的两个季节性队列的儿童，并在疟疾传播季节每月监测一次，同时在研究集群中随机选择的家庭中使用人诱捕（HLC）和疾病控制中心（CDC）诱蚊灯进行昆虫学监测。将队列参与者的行为数据与测量的致倦库蚊着陆率和疟原虫感染率相结合，以估计人类行为调整后的昆虫学接种率（EIR）。
在 20 个昆虫学监测集群中，1237 名儿童共进行了 5456 次儿童访视，将其行为数据与 8131 只雌性致倦库蚊通过 HLC 捕获的每小时着陆率相关联。在通过酶联免疫吸附试验（ELISA）检测的所有致倦库蚊中，有 3.3%呈疟原虫感染阳性。直接通过 HLC 测量的平均 EIR 为 0.07 个感染性叮咬/人/夜（ib/p/n）。当考虑到儿童夜间的位置时，行为调整后的平均 EIR 为 0.02 ib/p/n。未使用经杀虫剂处理的蚊帐（ITN）的儿童在 6 个月的季节中每人经历 13.6 次感染性叮咬，其中 8%发生在户外，而 ITN 用户每人经历 1.3 次感染性叮咬，其中 86%发生在户外。在 ITN 下睡觉可以预防约 90%的致倦库蚊叮咬。
在该环境中，由于致倦库蚊叮咬高峰期发生在室内，而大多数人都在睡觉，因此 ITN 具有很高的个体保护效力。然而，尽管家庭中 ITN 的拥有率很高（>90%），个人使用率也很高（>70%），但该环境中的儿童在 6 个月的传播季节中每人经历的感染性叮咬次数仍超过一次，足以维持高疟疾传播和负担。需要新的工具和策略来降低这种环境中的疟疾负担。
