Institute of Tropical Medicine, Nagasaki University, 1-12-4 Sakamoto, Nagasaki, Nagasaki, 852-8523, Japan.
College of Public Health, The University of Arizona, 1295 N Martin Ave, Tucson, AZ, 85724, USA.
Malar J. 2020 Oct 19;19(1):373. doi: 10.1186/s12936-020-03444-w.
Several types of insecticides, treating technologies and materials are available for long-lasting insecticide-treated nets (LLINs). The variations may result in different efficacies against mosquitoes and correspondingly infection risks for the Plasmodium falciparum malaria parasite. This cross-sectional study investigated whether infection risk varied among children who slept under different LLIN brands in rural villages of western Kenya.
Children sleeping under various types of LLINs were tested for P. falciparum infection using a diagnostic polymerase chain reaction (PCR) assay. Data were collected for other potential factors associated with infection risk: sleeping location (with bed/without bed), number of persons sharing the same net, dwelling wall material, gap of eaves (open/close), proportional hole index, socio-economic status, and density of indoor resting anophelines. Bed-net efficacy against the Anopheles gambiae susceptible strain was estimated using the WHO cone test and the tunnel test. The residual insecticide content on nets was measured.
Seven LLIN brands were identified, and deltamethrin-based DawaPlus® 2.0 was the most popular (48%) followed by permethrin-based Olyset® Net (28%). The former LLIN was distributed in the area about six months before the present study was conducted, and the latter net was distributed at least three years before. Of 254 children analysed, P. falciparum PCR-positive prevalence was 58% for DawaPlus® 2.0 users and 38% for Olyset® users. The multiple regression analysis revealed that the difference was statistically significant (adjusted OR: 0.67, 95% credible interval: 0.45-0.97), whereas the confounders were not statistically important. Among randomly selected net samples, all DawaPlus® 2.0 (n = 20) and 95% of Olyset® (n = 19) passed either the cone test or the tunnel test.
Olyset® was more effective in reducing infection risk compared with DawaPlus® 2.0. Although the data from the present study were too limited to explain the mechanism clearly, the results suggest that the characteristics of the former brand are more suitable for the conditions, such as vector species composition, of the study area.
长效驱虫蚊帐（LLIN）有多种杀虫剂类型、处理技术和材料。这些变化可能导致针对蚊子的效果不同，相应地也会影响疟原虫恶性疟原虫感染的风险。本横断面研究调查了在肯尼亚西部农村地区，不同品牌的 LLIN 对儿童的感染风险是否存在差异。
采用诊断聚合酶链反应（PCR）检测儿童是否感染恶性疟原虫。收集其他可能与感染风险相关的因素的数据：睡眠位置（与床同睡/不同床）、同网共用人数、居所墙壁材料、屋檐间隙（敞开/关闭）、比例孔指数、社会经济地位以及室内停歇按蚊密度。使用 WHO 锥形试验和隧道试验估计蚊帐对冈比亚按蚊敏感株的效果。测量网布上的残留杀虫剂含量。
共发现 7 种 LLIN 品牌，其中以使用最广泛的含氯菊酯的 DawaPlus® 2.0（48%）和含溴氰菊酯的 Olyset® Net（28%）为主。前者 LLIN 在本研究进行前约 6 个月在该地区分发，而后者至少在 3 年前分发。在 254 名接受分析的儿童中，DawaPlus® 2.0 用户的恶性疟原虫 PCR 阳性率为 58%，Olyset® 用户为 38%。多因素回归分析显示差异有统计学意义（调整后的 OR：0.67，95%可信区间：0.45-0.97），而混杂因素则无统计学意义。在随机选择的网布样本中，所有 DawaPlus® 2.0（n=20）和 95%的 Olyset®（n=19）均通过锥形试验或隧道试验。
与 DawaPlus® 2.0 相比，Olyset® 更能有效降低感染风险。尽管本研究的数据过于有限，无法清楚解释机制，但结果表明，前者品牌的特性更适合研究地区的蚊虫物种组成等情况。
