Rovira-Vallbona Eduard, Contreras-Mancilla Juan José, Ramirez Roberson, Guzmán-Guzmán Mitchel, Carrasco-Escobar Gabriel, Llanos-Cuentas Alejandro, Vinetz Joseph M, Gamboa Dionicia, Rosanas-Urgell Anna
Department of Biomedical Sciences, Institute of Tropical Medicine, Antwerp, Belgium.
Instituto de Medicina Tropical Alexander von Humboldt, Universidad Peruana Cayetano Heredia, Lima, Peru.
PLoS Negl Trop Dis. 2017 Jul 3;11(7):e0005674. doi: 10.1371/journal.pntd.0005674. eCollection 2017 Jul.
Malaria transmission requires that Anopheles mosquitoes ingest Plasmodium gametocyte stages circulating in the human bloodstream. In the context of malaria elimination, understanding the epidemiology of gametocytes relative to all Plasmodium infections and the contribution of asymptomatic and sub-microscopic parasite carriers to the gametocyte reservoir is necessary, especially in low endemic settings with predominance of P.vivax. A 13-month longitudinal study was conducted in two communities (n = 1935 individuals) of Loreto Department, Peru, with five active screenings for Plasmodium infections and gametocyte stages by quantitative real-time PCR (qPCR) and reverse transcription (RT)-qPCR, respectively. Parasite prevalence by qPCR was 7.2% for P.vivax (n = 520/7235; range by survey 6.0%-8.1%) and 3.2% for P.falciparum (n = 235/7235; range by survey 0.4%-7.7%). Sub-microscopic infections accounted for 73.5% of P.vivax (range by survey 60%-89%) and almost the totality of P.falciparum cases. Gametocytes were found in 28.4% P.vivax infections (range by survey 18.7%-34.1%), with a peak of 61.5% in one community at the start of the transmission season. About 59.8% of all P.vivax gametocyte carriers were asymptomatic and 31.9% were sub-microscopic. Age patterns for gametocyte prevalence paralleled asexual stage infections and peaked among >15-25 year old individuals. Asexual parasite density was found to be the strongest predictor for P.vivax gametocyte presence in longitudinal multivariate analysis (odds ratio 2.33 [95% confidence interval 1.96, 2.78]; P<0.001). Despite significant differences in seasonality patterns and P.vivax prevalence found at the local scale, sub-microscopic and asymptomatic infections predominate and contribute significantly to the gametocyte reservoir in different communities of the Peruvian Amazon. Control and elimination campaigns need sensitive tools to detect all infections that escape routine malaria surveillance, which may contribute to maintain transmission in the region.
疟疾传播需要按蚊摄取在人类血液中循环的疟原虫配子体阶段。在疟疾消除的背景下,了解配子体相对于所有疟原虫感染的流行病学情况以及无症状和亚显微镜下寄生虫携带者对配子体库的贡献是必要的,特别是在间日疟原虫占主导的低流行地区。在秘鲁洛雷托省的两个社区(n = 1935人)进行了一项为期13个月的纵向研究,分别通过定量实时PCR(qPCR)和逆转录(RT)-qPCR对疟原虫感染和配子体阶段进行了五次主动筛查。通过qPCR检测,间日疟原虫的寄生虫流行率为7.2%(n = 520/7235;各次调查范围为6.0%-8.1%),恶性疟原虫为3.2%(n = 235/7235;各次调查范围为0.4%-7.7%)。亚显微镜下感染占间日疟原虫感染的73.5%(各次调查范围为60%-89%),几乎占所有恶性疟原虫病例。在28.4%的间日疟原虫感染中发现了配子体(各次调查范围为18.7%-34.1%),在传播季节开始时,一个社区的配子体感染率峰值达到61.5%。所有间日疟原虫配子体携带者中约59.8%无症状,31.9%为亚显微镜下感染。配子体流行率的年龄模式与无性阶段感染相似,在15-25岁以上个体中达到峰值。在纵向多变量分析中,无性寄生虫密度被发现是间日疟原虫配子体存在的最强预测因素(优势比2.33 [95%置信区间1.96, 2.78];P<0.001)。尽管在当地尺度上发现季节性模式和间日疟原虫流行率存在显著差异,但亚显微镜下和无症状感染占主导地位,并对秘鲁亚马逊地区不同社区的配子体库有显著贡献。控制和消除运动需要灵敏的工具来检测所有逃避常规疟疾监测的感染,这些感染可能有助于维持该地区的传播。