Ethiopia has set a goal for malaria elimination by 2030. Low parasite density infections may go undetected by conventional diagnostic methods (microscopy and rapid diagnostic tests) and their contribution to malaria transmission varies by transmission settings. This study quantified the burden of subpatent infections from samples collected from three regions of northwest Ethiopia. Sub-samples of dried blood spots from the Ethiopian Malaria Indicator Survey 2015 (EMIS-2015) were tested and compared using microscopy, rapid diagnostic tests (RDTs), and nested polymerase chain reaction (nPCR) to determine the prevalence of subpatent infection. Paired seroprevalence results previously reported along with gender, age, and elevation of residence were explored as risk factors for Plasmodium infection. Of the 2608 samples collected, the highest positive rate for Plasmodium infection was found with nPCR 3.3% (95% CI 2.7–4.1) compared with RDT 2.8% (95% CI 2.2–3.5) and microscopy 1.2% (95% CI 0.8–1.7). Of the nPCR positive cases, Plasmodium falciparum accounted for 3.1% (95% CI 2.5–3.8), Plasmodium vivax 0.4% (95% CI 0.2–0.7), mixed P. falciparum and P. vivax 0.1% (95% CI 0.0–0.4), and mixed P. falciparum and Plasmodium malariae 0.1% (95% CI 0.0–0.3). nPCR detected an additional 30 samples that had not been detected by conventional methods. The majority of the nPCR positive cases (61% (53/87)) were from the Benishangul-Gumuz Region. Malaria seropositivity had significant association with nPCR positivity [adjusted OR 10.0 (95% CI 3.2–29.4), P < 0.001]. Using nPCR the detection rate of malaria parasites increased by nearly threefold over rates based on microscopy in samples collected during a national cross-sectional survey in 2015 in Ethiopia. Such subpatent infections might contribute to malaria transmission. In addition to strengthening routine surveillance systems, malaria programmes may need to consider low-density, subpatent infections in order to accelerate malaria elimination efforts.

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埃塞俄比亚西北部亚专利疟原虫感染的评估

埃塞俄比亚设定了到2030年消除疟疾的目标。传统的诊断方法（显微镜和快速诊断测试）可能无法发现低寄生虫密度感染，并且其对疟疾传播的贡献因传播方式而异。这项研究量化了从埃塞俄比亚西北部三个地区收集的样本中亚专利感染的负担。测试并比较了2015年埃塞俄比亚疟疾指标调查（EMIS-2015）的干血斑子样本，并使用显微镜，快速诊断测试（RDT）和巢式聚合酶链反应（nPCR）进行比较以确定亚专利感染的患病率。探讨了先前报告的成对血清阳性率结果以及性别，年龄和居住地升高，作为疟原虫感染的危险因素。在收集的2608个样本中，nPCR 3.3％（95％CI 2.7-4.1）发现疟原虫感染的最高阳性率，RDT 2.8％（95％CI 2.2-3.5）和显微镜检查发现1.2％（95％CI 0.8-1.7）。在nPCR阳性病例中，恶性疟原虫占3.1％（95％CI 2.5-3.8），间日疟原虫占0.4％（95％CI 0.2-0.7），恶性疟原虫和间日疟原虫占0.1％（95％CI 0.0- 0.4），并混合恶性疟原虫和疟原虫0.1％（95％CI 0.0-0.3）。nPCR检测到另外30个常规方法未检测到的样品。大多数nPCR阳性病例（61％（53/87））来自贝尼桑古尔-古穆兹地区。疟疾血清阳性与nPCR阳性显着相关[校正OR 10.0（95％CI 3.2-29.4），P <0.001]。使用nPCR，2015年埃塞俄比亚全国横断面调查期间收集的样本中，使用显微镜检测的疟原虫检出率比显微镜检出率高出近三倍。这种亚专利感染可能导致疟疾传播。除加强常规监测系统外，疟疾规划可能还需要考虑低密度亚专利感染，以加快消除疟疾的工作。