Department of Medical Laboratory Sciences, College of Medicine and Health Sciences, Arba Minch University, Arba Minch, Ethiopia.
School of Medical Laboratory Sciences, Faculty of Health Sciences, Jimma University, Jimma, Ethiopia.
Malar J. 2024 Nov 29;23(1):362. doi: 10.1186/s12936-024-05171-y.
Identification of local Plasmodium vivax transmission foci and its hidden reservoirs are crucial to eliminating residual vivax malaria transmission. This study assessed whether reactive case detection (RCD) could better identify P. vivax cases and infection incidences in Arjo-Didessa, Southwestern Ethiopia.
A RCD survey was conducted from November 2019 to October 2021 in Arjo-Didessa and the surrounding vicinity in southwestern Ethiopia. RCD was performed at 0, 30, and 60 days following reports of P. vivax infections by health facilities to detect further cases and potential transmission networks. Household members of the index case and neighbours living within 200 m of the index household were screened for P. vivax. Households 200-500 m away are considered controls and were also screened for P. vivax. Plasmodium vivax was detected by microscopy, rapid diagnostic testing (RDT), and quantitative polymerase chain reaction (qPCR). Risk factors associated with vivax malaria were analysed using generalized estimating equations (GEE).
A total of 3303 blood samples were collected from the index (n = 427), neighbouring (n = 1626), and control (n = 1240) household in the three rounds of follow-up visits for malaria infection, the overall positivity rate of P. vivax malaria was 1.6% (95% CI 1.2-2.2%), 1.9% (95% CI 1.5-2.4), and 3.9% (95% CI 3.2-4.6%) by microscopy, RDT, and qPCR, respectively. Microscopy and RDT detected 41.5% (54 of 130) and 49.1% (64 of 130) of the qPCR-confirmed P. vivax cases, respectively. Of qPCR-positive samples, 77.7% of the total P. vivax infections circulated in the index and neighbouring households, while control households accounted for 23.3% of the infections. Of the P. vivax infections detected 81.0% (95% CI 72.9-87.1%) were asymptomatic. In this study, P. vivax infection incidence was higher in index case households (53.8 cases per 1000 person-months) and (44.0 cases per 1000 person-months) in neighbouring households compared to the control households (25.1 cases per 1000 person-months) with statistical difference (p = 0.02). In index case households, children < 5 years and school-age children were at higher risk of P. vivax infection (AOR: 6.3, 95% CI: 2.24-18.02, p = 0.001 and AOR: 2.7, 95% CI: 1.10-6.64, p = 0.029).
This study found clustering of asymptomatic and sub-microscopic P. vivax infections in the index case household and their neighbours using RCD and molecular methods. Children under 5 years and of school age were more likely to have P. vivax infection in index households. Thus, tailored RCD approaches and targeted interventions for interrupting residual P. vivax transmission networks are needed to eliminate P. vivax malaria in low transmission settings.
鉴定局部间日疟传播焦点及其隐匿性储存宿主对于消除残余间日疟传播至关重要。本研究评估了在埃塞俄比亚西南部的 Arjo-Didessa 及其周边地区，采用反应性病例检测（RCD）是否能更好地发现间日疟病例和感染发生率。
2019 年 11 月至 2021 年 10 月期间，在埃塞俄比亚西南部的 Arjo-Didessa 及周边地区进行了 RCD 调查。在医疗机构报告间日疟感染后 0、30 和 60 天进行 RCD，以发现进一步的病例和潜在的传播网络。对索引病例的家庭成员和居住在索引家庭 200 米范围内的邻居进行间日疟筛查。距离 200-500 米的家庭被视为对照，也进行间日疟筛查。通过显微镜检查、快速诊断检测（RDT）和定量聚合酶链反应（qPCR）检测间日疟原虫。使用广义估计方程（GEE）分析与间日疟相关的风险因素。
在三轮随访中，共从索引（n=427）、相邻（n=1626）和对照（n=1240）家庭中采集了 3303 份血样进行疟疾感染检测，间日疟感染的总阳性率分别为 1.6%（95%CI 1.2-2.2%）、1.9%（95%CI 1.5-2.4%）和 3.9%（95%CI 3.2-4.6%），分别通过显微镜、RDT 和 qPCR 检测。显微镜和 RDT 分别检测到 41.5%（54/130）和 49.1%（64/130）的 qPCR 确认的间日疟病例。在 qPCR 阳性样本中，77.7%的总间日疟感染发生在索引和相邻家庭中，而对照家庭占 23.3%的感染。在检测到的间日疟感染中，81.0%（95%CI 72.9-87.1%）为无症状感染。在这项研究中，与对照家庭（25.1 例/1000 人月）相比，索引病例家庭（53.8 例/1000 人月）和相邻家庭（44.0 例/1000 人月）的间日疟感染发病率更高，具有统计学差异（p=0.02）。在索引病例家庭中，5 岁以下儿童和学龄儿童患间日疟的风险更高（AOR：6.3，95%CI：2.24-18.02，p=0.001 和 AOR：2.7，95%CI：1.10-6.64，p=0.029）。
本研究使用 RCD 和分子方法发现，索引病例家庭及其邻居存在无症状和亚显微间日疟感染聚集。5 岁以下和学龄儿童在索引家庭中更有可能感染间日疟。因此，需要采取有针对性的 RCD 方法和干预措施，以阻断残余间日疟传播网络，从而在低传播环境中消除间日疟。
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