Field Epidemiology and Laboratory Training Program, Ministry of Health, Nairobi, Kenya.
The U.S. Centers for Disease Control and Prevention, Nairobi, Kenya.
PLoS One. 2022 Apr 20;17(4):e0266736. doi: 10.1371/journal.pone.0266736. eCollection 2022.
Long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS) are the main malaria vector control measures deployed in Kenya. Widespread pyrethroid resistance among the primary vectors in Western Kenya has necessitated the re-introduction of IRS using an organophosphate insecticide, pirimiphos-methyl (Actellic® 300CS), as a pyrethroid resistance management strategy. Evaluation of the effectiveness of the combined use of non-pyrethroid IRS and LLINs has yielded varied results. We aimed to evaluate the effect of non-pyrethroid IRS and LLINs on malaria indicators in a high malaria transmission area.
We reviewed records and tallied monthly aggregate of outpatient department (OPD) attendance, suspected malaria cases, those tested for malaria and those testing positive for malaria at two health facilities, one from Nyatike, an intervention sub-county, and one from Suba, a comparison sub-county, both located in Western Kenya, from February 1, 2016, through March 31, 2018. The first round of IRS was conducted in February-March 2017 in Nyatike sub-county and the second round one year later in both Nyatike and Suba sub-counties. The mass distribution of LLINs has been conducted in both locations. We performed descriptive analysis and estimated the effect of the interventions and temporal changes of malaria indicators using Poisson regression for a period before and after the first round of IRS.
A higher reduction in the intervention area in total OPD, the proportion of OPD visits due to suspected malaria, testing positivity rate and annual malaria incidences were observed except for the total OPD visits among the under 5 children (59% decrease observed in the comparison area vs 33% decrease in the intervention area, net change -27%, P <0.001). The percentage decline in annual malaria incidence observed in the intervention area was more than twice the observed percentage decline in the comparison area across all the age groups. A marked decline in the monthly testing positivity rate (TPR) was noticed in the intervention area, while no major changes were observed in the comparison area. The monthly TPR reduced from 46% in February 2016 to 11% in February 2018, representing a 76% absolute decrease in TPR among all ages (RR = 0.24, 95% CI 0.12-0.46). In the comparison area, TPR was 16% in both February 2016 and February 2018 (RR = 1.0, 95% CI 0.52-2.09). A month-by-month comparison revealed lower TPR in Year 2 compared to Year 1 in the intervention area for most of the one year after the introduction of the IRS.
Our findings demonstrated a reduced malaria burden among populations protected by both non-pyrethroid IRS and LLINs implying a possible additional benefit afforded by the combined intervention in the malaria-endemic zone.
长效杀虫蚊帐（LLINs）和室内滞留喷洒（IRS）是肯尼亚部署的主要疟疾病媒控制措施。在西肯尼亚主要病媒中广泛存在拟除虫菊酯抗药性，这使得有必要重新引入有机磷杀虫剂，如派卡瑞丁（Actellic® 300CS），作为拟除虫菊酯抗药性管理策略。评估非拟除虫菊酯 IRS 和 LLINs 联合使用的效果得出了不同的结果。我们旨在评估非拟除虫菊酯 IRS 和 LLINs 在高疟疾传播地区对疟疾指标的影响。
我们回顾了记录，并统计了两家卫生机构每月的门诊就诊量、疑似疟疾病例数、接受疟疾检测的病例数和检测阳性的病例数，这两家卫生机构分别位于 Nyatike（干预次县）和 Suba（对照次县），均位于肯尼亚西部，从 2016 年 2 月 1 日至 2018 年 3 月 31 日。第一轮 IRS 于 2017 年 2 月至 3 月在 Nyatike 次县进行，第二轮 IRS 于一年后在 Nyatike 和 Suba 次县进行。在这两个地方都进行了大规模的 LLIN 分发。我们进行了描述性分析，并使用泊松回归估计了干预措施和疟疾指标时间变化的效果，分析时间段为第一轮 IRS 之前和之后。
干预地区的总门诊就诊量、因疑似疟疾就诊的比例、检测阳性率和年疟疾发病率均有较高的降低，除了 5 岁以下儿童的总门诊就诊量（干预地区的降幅为 59%，对照地区的降幅为 33%，净变化为-27%，P <0.001）。干预地区观察到的年疟疾发病率下降百分比是对照地区的两倍多。干预地区的每月检测阳性率（TPR）明显下降，而对照地区没有明显变化。TPR 从 2016 年 2 月的 46%下降到 2018 年 2 月的 11%，代表所有年龄段的 TPR 绝对下降了 76%（RR = 0.24，95%CI 0.12-0.46）。在对照地区，2016 年 2 月和 2018 年 2 月的 TPR 均为 16%（RR = 1.0，95%CI 0.52-2.09）。逐月比较显示，在 IRS 引入后的一年中，干预地区的 TPR 在第二年比第一年低。
我们的研究结果表明，在非拟除虫菊酯 IRS 和 LLINs 保护下的人群中疟疾负担减轻，这表明在疟疾流行地区联合干预可能提供了额外的益处。
