Evaluating the determinants of the spread of COVID-19 between and within rural communities in Mali, West Africa based on blood-fed mosquitoes

基于吸血蚊子评估西非马里农村社区之间和内部 COVID-19 传播的决定因素

• 批准号: 10927969
• 负责人: Tovi Lehmann
• 金额: $ 115.57万
• 依托单位: NATIONAL INSTITUTE OF ALLERGY AND INFECTIOUS DISEASES
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10927969
• 关键词: 2019-nCoV; 3 year old; Affect; Africa; Africa South of the Sahara; African; Age; Americas; Antibodies; Antibody titer measurement; Antigens; Area; Arteries; Asia; Biological Assay; Blood; Blood specimen; COVID-19; COVID-19 monitoring; Cities; Communities; Country; Culicidae; Data; Disease Surveillance; Distant; Environment; Enzyme-Linked Immunosorbent Assay; Epidemiology; Europe; Exposure to; Female; Goals; Home; Hour; Human; Human Bites; Immunoassay; Immunoglobulin G; Individual; Infection; Laboratories; Mali; Marketing; Measures; Monitor; Nucleocapsid; Paper; Persons; Population; Printing; Process; Protocols documentation; Public Health; Publishing; Rest; Role; Route; Rural; Rural Community; SARS-CoV-2 infection; SARS-CoV-2 transmission; Sampling; Schools; Serology; Seroprevalences; Shapes; Site; Specificity; Specimen; System; Techniques; Time; Transportation; United States National Institutes of Health; Virus; Visit; Widespread Disease; Work; antibody detection; antibody test; aspirate; density; epidemiologic data; epidemiology study; experimental study; feeding; frontier; human disease; novel; pandemic disease; pre-pandemic; receptor binding; rural setting; seropositive; serosurveillance; spatiotemporal; vector-borne

The spread of COVID-19 in rural sub-Saharan Africa is poorly understood and reliable data are unlikely to be obtained as a result of low capacity for disease surveillance, compounded by high proportion of young population that present mostly asymptomatic or low-symptomatic infections. To fill this gap and assess how the unique ecological and cultural settings affect it, we have initiated a novel epidemiological study, monitoring COVID-19 infections by sampling blood-fed mosquitoes collected monthly in houses of 20 Malian villages spread across 500km. By May 2022, a total of 48,805 females mosquitoes were collected over 27,900 house visits from 20 villages. We expect at least 30,000 females being blood-fed. Experiments using these and laboratory mosquitoes were carried out in Mali and in NIH to provide a proof of concept to the feasibility of this project as a prerequisite before expansion to the full scope of this work. Immunoglobulin-G antibodies were found to be readily detectable within the mosquito bloodmeals by a bead-based immunoassay through 10 (and up to 30) hours post-feeding, indicating that most mosquitoes collected via indoor aspiration catches (that likely fed the previous night and are now resting), are viable samples for analysis. Using 90 pre-pandemic bloodfed mosquitoes we established antigen specific cutoffs (mean 5*STD) for antibodies against the i) nucleocapsid, ii) the receptor binding domain (RBD), and iii-iv) the two spike domains, to identify mosquitoes that fed on Covid-seropositive and seronegative humans. By requiring at least 2 antibody titers to exceed their cutoffs the estimated sensitivity was 0.90 (+/=0.059) and specificity was 0.92 (+/-0.080), indicating that most blood-fed mosquitoes collected by early morning indoors, have likely fed the previous night, and are viable samples for analysis. Using this assay, we evaluated the change in sero-prevalence of one urban and four rural communities in Mali. Consistent with, albeit somewhat lower than, a conventional serological study in Mali (Sagara et al. 2021), crude sero-positivity of blood sampled via mosquitoes was 6.3% in October/November 2020 over all sites, and increased to 25.1% overall, with the town closest to Bamako (Sotuba) reaching 46.7% in February of 2021. Adjusted to mosquitoes feeding on non-human hosts and to the possibility of multiple mosquitoes feeding on the same individual human changed the results little because most mosquitoes fed on human blood and relatively small number of mosquitoes were analyzed from each house at a period. In finding this a viable technique amenable to conventional immunoassays to measure population-level sero-prevalance, we feel sero-surveillance of human diseases, regardless if they are vector-borne, is attainable, non-invasive sampling option, especially suited to areas with high density of human-biting mosquitoes. Our first paper (Krajacich et al. 2023) summarizing the results of 5 villages at two time points is currently Under Review in Frontiers in Epidemiology after the preprint was published in medRxiv: https://www.medrxiv.org/content/10.1101/2023.06.13.23291267v1. Additionally, our team in Mali has been performing ELISA assays to detect antibodies against the Spike and RBD based on protocols optimized by the group of Patrick Duffy (LMIV). Currently over 4,000 mosquitoes were assayed for both antigens. Based on cutoffs established for these ELISA assays in Mali (Woodford et al. 2021), overall seroprevalence rates increased from 21.9% in October 2020 to 51.2% in January-February 2021 (21=55.4, P<0.001), in accord with sero-prevalence change measured in resident of 3 Malian communities (Sagara et al. 2022). Note that the assortment of villages used in this study was different from the subset used in the four-antigen bead assay (above). Our goal is to complete the assays on 12,000 blood-fed mosquitoes representing multiple time points from October 2020 to September 2022 from 20 rural communities, which will provide the dynamics of spread of COVID-19 in Mali during the first years of the pandemic.

人们对新冠肺炎在撒哈拉以南非洲农村地区的传播情况知之甚少，而且由于疾病监测能力低，再加上年轻人大多无症状或无症状感染的比例很高，因此不太可能获得可靠的数据。为了填补这一空白，并评估独特的生态和文化环境对其的影响，我们启动了一项新的流行病学研究，通过对分布在500公里的马里20个村庄的房屋中每月收集的吸血蚊子进行采样，监测新冠肺炎感染情况。截至2022年5月，在20个村庄的27,900次家访中，总共收集了48,805只雌性蚊子。我们预计至少有30,000只雌性被喂血。在马里和国立卫生研究院进行了使用这些蚊子和实验室蚊子的实验，以便在扩大这项工作的全部范围之前，作为先决条件，对这一项目的可行性提供概念证明。 在喂食后10小时(最多30小时)，通过基于珠粒的免疫分析，在蚊子血粉中很容易检测到免疫球蛋白-G抗体，这表明通过室内吸引器收集的大多数蚊子(可能是前一天晚上吸食的蚊子，现在正在休息)是可以进行分析的样本。使用90只大流行前吸血的蚊子，我们建立了针对I)核衣壳、II)受体结合域(RBD)和III-IV两个尖峰结构域的抗体的抗原特异性界值(平均5*STD)，以识别以Covid血清阳性和血清阴性人类为食的蚊子。通过要求至少2个抗体效价超过它们的临界值，估计的敏感性为0.9(+/=0.059)，特异性为0.92%(+/-0.080)，这表明大多数在室内清晨采集的吸血蚊子很可能在前一天晚上进食过，是可行的分析样本。 使用这一检测方法，我们评估了马里一个城市和四个农村社区的血清流行率的变化。与马里的常规血清学研究一致，尽管略低于该研究(Sagara等人。2021年)，2020年10月/11月，所有地点通过蚊子采集的血液粗略血清阳性率为6.3%，总体上升到25.1%，其中距离巴马科(索图巴)最近的城镇在2021年2月达到46.7%。适应了以非人类宿主为食的蚊子，以及多只蚊子以同一个人为食的可能性，结果变化不大，因为大多数蚊子以人血为食，而相对较少的蚊子是在一段时间内从每个房子中分析出来的。在发现这是一种符合传统免疫分析的可行技术来衡量人群水平的血清流行率时，我们认为对人类疾病进行血清监测是可行的，无论这些疾病是否由媒介传播，都是可以实现的非侵入性抽样选择，特别适合于叮咬人的蚊子密度高的地区。我们的第一篇论文(克拉贾西奇等人)2023年)在MedRxiv：https://www.medrxiv.org/content/10.1101/2023.06.13.23291267v1.上发表预印本后，目前正在审查《流行病学前沿》杂志上对两个时间点的5个村庄的结果进行总结 此外，我们在马里的团队一直在根据Patrick Duffy(LMIV)小组优化的方案进行ELISA检测，以检测针对Spike和RBD的抗体。目前，对4000多只蚊子进行了这两种抗原的检测。根据马里为这些酶联免疫吸附试验确定的截止值(Woodford等人。2021年)，总体血清阳性率从2021年10月的21.9%上升到2021年1-2月的51.2%(21=55.4P&lt；0.001)，与马里3个社区居民测量的血清流行率变化一致(Sagara等人)。2022年)。请注意，这项研究中使用的村落分类与四抗原珠分析中使用的子集不同(如上)。我们的目标是从2020年10月到2022年9月完成对来自20个农村社区的12,000只采血蚊子的检测，这些蚊子代表了多个时间点，这将提供新冠肺炎在马里大流行头几年的传播动态。