Department of Biochemistry and Microbiology, University of Namibia School of Medicine, Windhoek, Namibia.
National Vector Borne Disease Control Program, Ministry of Health and Social Services, Windhoek, Namibia.
PLoS Negl Trop Dis. 2019 May 1;13(5):e0007290. doi: 10.1371/journal.pntd.0007290. eCollection 2019 May.
Knowledge of the foci of Plasmodium species infections is critical for a country with an elimination agenda. Namibia is targeting malaria elimination by 2020. To support decision making regarding targeted intervention, we examined for the first time, the foci of Plasmodium species infections and regional prevalence in northern Namibia, using nested and quantitative polymerase chain reaction (PCR) methods.
We used cross-sectional multi-staged sampling to select 952 children below 9 years old from schools and clinics in seven districts in northern Namibia, to assess the presence of Plasmodium species.
The median participant age was 6 years (25-75%ile 4-8 y). Participants had a median hemoglobin of 12.0 g/dL (25-75%ile 11.1-12.7 g/dL), although 21% of the cohort was anemic, with anemia being severer in the younger population (p<0.002). Most of children with Plasmodium infection were asymptomatic (63.4%), presenting a challenge for elimination. The respective parasite prevalence for Plasmodium falciparum (Pf), Plasmodium vivax (Pv) and Plasmodium ovale curtisi (Po) were (4.41%, 0.84% and 0.31%); with Kavango East and West (10.4%, 6.19%) and Ohangwena (4.5%) having the most prevalence. Pv was localized in Ohangwena, Omusati and Oshana, while Po was found in Kavango. All children with Pv/Pf coinfections in Ohangwena, had previously visited Angola, affirming that perennial migrations are risks for importation of Plasmodium species. The mean hemoglobin was lower in those with Plasmodium infection compared to those without (0.96 g/dL less, 95%CI 0.40-1.52 g/dL less, p = 0.0009) indicating that quasi-endemicity exists in the low transmission setting.
We conclude that Pv and Po species are present in northern Namibia. Additionally, the higher number of asymptomatic infections present challenges to the efforts at elimination for the country. Careful planning, coordination with neighboring Angola and execution of targeted active intervention, will be required for a successful elimination agenda.
了解疟原虫感染的焦点对于一个有消除目标的国家至关重要。纳米比亚的目标是在 2020 年消除疟疾。为了支持针对目标干预的决策，我们首次使用巢式和定量聚合酶链反应（PCR）方法，检查了纳米比亚北部疟原虫感染的焦点和区域流行率。
我们使用横断面多阶段抽样方法，从纳米比亚北部七个地区的学校和诊所中选择了 952 名 9 岁以下的儿童，以评估疟原虫的存在。
参与者的中位年龄为 6 岁（25-75%为 4-8 岁）。参与者的中位血红蛋白为 12.0g/dL（25-75%为 11.1-12.7g/dL），尽管 21%的患者贫血，年轻人群贫血更严重（p<0.002）。大多数感染疟原虫的儿童无症状（63.4%），这对消除疟疾构成了挑战。恶性疟原虫（Pf）、间日疟原虫（Pv）和卵形疟原虫（Po）的寄生虫患病率分别为（4.41%、0.84%和 0.31%）；东、西卡万戈（10.4%、6.19%）和奥汉圭纳（4.5%）的患病率最高。Pv 局限于奥汉圭纳、奥姆沙蒂和奥什纳，而 Po 则在卡万戈发现。奥汉圭纳所有感染 Pv/Pf 的儿童均曾前往安哥拉，证实常年迁徙是输入疟原虫的风险。与未感染的儿童相比，感染的儿童平均血红蛋白水平更低（低 0.96g/dL，95%置信区间为 0.40-1.52g/dL，p=0.0009），表明在低传播环境中存在准地方性。
我们的结论是，纳米比亚北部存在 Pv 和 Po 物种。此外，大量无症状感染给该国的消除工作带来了挑战。需要精心规划、与邻国安哥拉协调并实施有针对性的主动干预，才能成功实现消除目标。
