Center for Vaccine Development and Global Health, University of Maryland School of Medicine, 685 W, Baltimore Street, Baltimore, MD, 21201, USA.
University of Colorado School of Public Health, University of Colorado, 13001 E, 17th Place, Mail Stop B119, Aurora, CO, 80045, USA.
Malar J. 2019 Sep 24;18(1):329. doi: 10.1186/s12936-019-2930-8.
Distribution campaigns for insecticide-treated nets (ITN) have increased the use of ITNs in Malawi, but malaria prevalence remains high even among those using the nets. Previous studies have addressed ITN ownership, insecticide resistance, and frequency of ITN use as possible contributing factors to the high prevalence of malaria infection despite high ITN coverage, but have rarely considered whether the condition of the ITN, or how many people use it, impacts efficacy. This study assessed how ITN integrity, ITN age, and the number of persons sharing a net might mitigate or reduce protective efficacy among self-identified ITN users in Malawi.
From 2012 to 2014, six cross-sectional surveys were conducted in both the rainy and dry seasons in southern Malawi. Data were collected on ITN use, integrity (number and size of holes), and age. Blood samples for detecting Plasmodium falciparum infection were obtained from reported ITN users over 6 months of age. Generalized linear mixed models were used to account for clustering at the household and community level. The final model controlled for gender, household eaves, and community-level infection prevalence during the rainy season.
There were 9646 ITN users with blood samples across six surveys, 15% of whom tested positive for P. falciparum infection. Among children under 5 years old, there was a 50% increased odds of P. falciparum infection among those sleeping under an ITN older than two years, compared to those using an ITN less than 2 years old (OR = 1.50; 95% CI 1.07-2.08). ITN integrity and number of individuals sharing an ITN were not associated with P. falciparum infection.
Older ITNs were associated with higher rates of P. falciparum in young children, which may indicate that insecticide concentrations play a larger role in infection prevention than the physical barrier of an ITN. ITN use was self-reported and the integrity measures lacked the precision of newer methods, suggesting a need for objective measures of ITN use and more precise assessment of ITN integrity.
杀虫剂处理过的蚊帐（ITN）分发运动增加了马拉维 ITN 的使用，但即使在使用蚊帐的人群中，疟疾的发病率仍然很高。以前的研究已经解决了 ITN 所有权、杀虫剂耐药性以及 ITN 使用频率等问题，这些问题可能是尽管 ITN 覆盖率很高，但疟疾感染率仍然很高的原因，但很少考虑 ITN 的状况或有多少人使用它，这会影响疗效。本研究评估了 ITN 的完整性、ITN 的年龄以及共用一个蚊帐的人数如何减轻或降低马拉维自我认定的 ITN 用户的保护效力。
2012 年至 2014 年，在马拉维南部的雨季和旱季进行了六次横断面调查。收集了 ITN 使用情况、完整性（孔的数量和大小）和年龄的数据。从报告使用 ITN 超过 6 个月的人群中采集血液样本，以检测疟原虫感染。使用广义线性混合模型来解释家庭和社区层面的聚类。最终模型控制了性别、家庭屋檐和雨季社区层面的感染率。
共有 9646 名 ITN 用户在六次调查中提供了血液样本，其中 15%的人疟原虫感染检测呈阳性。在 5 岁以下儿童中，与使用不到 2 年的 ITN 的儿童相比，使用超过 2 年的 ITN 的儿童感染疟原虫的几率增加了 50%（比值比=1.50；95%置信区间 1.07-2.08）。ITN 的完整性和共用 ITN 的人数与疟原虫感染无关。
较老的 ITN 与幼儿中较高的疟原虫感染率有关，这可能表明杀虫剂浓度在预防感染方面的作用大于 ITN 的物理屏障。ITN 的使用是自我报告的，完整性测量缺乏较新方法的精度，这表明需要对 ITN 的使用进行客观测量，并更精确地评估 ITN 的完整性。
