Novartis Pharmaceuticals Corporation, One Health Plaza, East Hanover, NJ 07936-1080, USA.
BMC Infect Dis. 2013 Nov 12;13:535. doi: 10.1186/1471-2334-13-535.
In malaria-endemic countries, large proportions of individuals infected with Plasmodium falciparum are asymptomatic and constitute a reservoir of parasites for infection of newly hatched mosquitoes.
Two studies were run in parallel in Burkina Faso to evaluate the impact of systematic identification and treatment of asymptomatic carriers of P. falciparum, detected by rapid diagnostic test, on disease transmission and susceptibility to clinical malaria episodes. A clinical study assessed the incidence of symptomatic malaria episodes with a parasite density >5,000/μL after three screening and treatment campaigns ~1 month apart before the rainy season; and an entomological study determined the effect of these campaigns on malaria transmission as measured by entomological inoculation rate.
The intervention arm had lower prevalence of asymptomatic carriers of asexual parasites and lower prevalence of gametocyte carriers during campaigns 2 and 3 as compared to the control arm. During the entire follow-up period, out of 13,767 at-risk subjects, 2,516 subjects (intervention arm 1,332; control arm 1,184) had symptomatic malaria. Kaplan-Meier analysis of the incidence of first symptomatic malaria episode with a parasite density >5,000/μL showed that, in the total population, the two treatment arms were similar until Week 11-12 after campaign 3, corresponding with the beginning of the malaria transmission season, after which the probability of being free of symptomatic malaria was lower in the intervention arm (logrank p < 0.0001). Similar trends were observed in infants and children <5 years and in individuals ≥5 years of age. In infants and children <5 years old who experienced symptomatic malaria episodes, the geometric mean P. falciparum density was lower in the intervention arm than the control arm. This trend was not seen in those individuals aged ≥5 years. Over the year, monthly variation in mosquito density and entomological inoculation rate was comparable in both arms, with September peaks in both indices.
Community screening and targeted treatment of asymptomatic carriers of P. falciparum had no effect on the dynamics of malaria transmission, but seemed to be associated with an increase in the treated community's susceptibility to symptomatic malaria episodes after the screening campaigns had finished. These results highlight the importance of further exploratory studies to better understand the dynamics of disease transmission in the context of malaria elimination.
在疟疾流行国家，很大比例的感染恶性疟原虫的个体无症状，构成了新孵化蚊子感染的寄生虫库。
在布基纳法索同时进行了两项研究，以评估通过快速诊断检测系统识别和治疗无症状恶性疟原虫携带者对疾病传播和易感性的影响。一项临床研究评估了在雨季前一个月内进行三次筛查和治疗后，寄生虫密度>5000/μL 的有症状疟疾病例的发生率；一项昆虫学研究确定了这些活动对蚊媒接种率衡量的疟疾传播的影响。
与对照组相比，干预组在第 2 次和第 3 次干预期间，无寄生虫血症携带者的患病率和配子体携带者的患病率较低。在整个随访期间，在 13767 名高危人群中，有 2516 名（干预组 1332 名，对照组 1184 名）出现有症状的疟疾。Kaplan-Meier 分析首次寄生虫密度>5000/μL 的有症状疟疾的发生率表明，在总人群中，两个治疗组在第 3 次干预后 11-12 周（即疟疾传播季节开始）之前相似，之后干预组无症状疟疾的可能性较低（对数秩检验 p<0.0001）。在婴儿和<5 岁的儿童以及≥5 岁的个体中也观察到类似的趋势。在经历有症状疟疾的婴儿和<5 岁的儿童中，干预组的恶性疟原虫密度比对照组低。在≥5 岁的个体中未观察到这种趋势。在一年中，两个组的蚊密度和蚊媒接种率逐月变化相当，9 月为两个指标的高峰期。
社区筛查和针对恶性疟原虫无症状携带者的靶向治疗对疟疾传播动态没有影响，但似乎与筛查活动结束后治疗社区对有症状疟疾发作的易感性增加有关。这些结果强调了进一步探索性研究的重要性，以更好地了解消除疟疾背景下疾病传播的动态。
