Declining malaria transmission in rural Amazon: changing epidemiology and challenges to achieve elimination
Declining malaria transmission in rural Amazon: changing epidemiology and challenges to achieve elimination
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DOI：
10.1186/s12936-016-1326-2
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发表时间：
2016-05-10
期刊：
影响因子：
3
通讯作者：
Guimaraes Lacerda, Marcus Vinicius
中科院分区：
文献类型：
--
作者：
Vitor-Silva, Sheila;Siqueira, Andre Machado;Guimaraes Lacerda, Marcus Vinicius
背景：近年来，巴西在降低其发病率方面取得了相当大的成功，导致间日疟原虫引起的病例比例相对增加，间日疟原虫被认为是一种更难消灭的寄生虫。本研究的目的是描述巴西西部亚马逊地区农村居民点地区的传播动态和相关危险因素。方法：在农村居民点建立前瞻性队列研究，为期3年。随访包括连续被动病例检测和每月主动病例检测，为期6个月。收集了人口统计、临床和传播控制实践数据。通过血涂片进行疟疾诊断。采用负二项回归模型对与疟疾发病率相关的因素进行单变量和多变量分析。使用单变量和多变量cox -比例风险模型分析了与前一次发作后90天内间日疟原虫和恶性疟原虫疟疾复发相关的因素。结果：疟疾流行率从研究开始时的7%下降到第24个月时的0.6%，随访1年后间日疟原虫占主导地位，恶性疟原虫消失。旱季疟疾发病率显著增高[IRR (95% CI) 1.4 (1.1 ~ 1.6)；P < 0.001)。使用ITN与地方疟疾防护相关[IRR (95% CI) 0.7 (0.6-0.8)；P = 0.001)]。在初次诊断后90天内观察到29.4%的个体复发间日疟原虫发作。既往间日疟原虫[IRR (95% CI) 2.3 (1.3-4.0)；p = 0.006)]或间日疟原虫+恶性疟原虫混合感染[IRR (95% CI) 2.9 (1.5-5.7)；P = 0.002)]感染与随访90天内间日疟疾发作显著相关。结论：在恶性疟原虫和间日疟原虫共流行的地区，恶性疟原虫实际上消失了，间日疟原虫的相对贡献增加了，反复发作的比例很大。这一发现加强了恶性疟原虫对早期诊断和治疗以及ITN使用的反应更敏感的看法，以及间日疟原虫复发对维持该物种传播的贡献。在间日疟原虫流行地区，评估不同传播强度的抗催眠虫治疗效果可能是控制和消除疟疾的一项基本工作。
Background: In recent years, considerable success in reducing its incidence has been achieved in Brazil, leading to a relative increase in the proportion of cases caused by Plasmodium vivax, considered a harder-to-eliminate parasite. This study aim is to describe the transmission dynamics and associated risk factors in a rural settlement area in the Western Brazilian Amazon.Methods: A prospective cohort was established in a rural settlement area for 3 years. Follow-up included continuous passive case detection and monthly active case detection for a period of 6 months. Demographic, clinical and transmission control practices data were collected. Malaria diagnosis was performed through thick blood smear. Univariable and multivariable analyses of factors associated with malaria incidence were performed using negative binomial regression models. Factors associated with recurrence of P. vivax and Plasmodium falciparum malaria within 90 days of a previous episode were analysed using univariable and multivariable Cox-Proportional Hazard models.Results: Malaria prevalence decreased from 7 % at the study beginning to 0.6 % at month 24, with P. vivax predominating and P. falciparum disappearing after 1 year of follow-up. Malaria incidence was significantly higher in the dry season [IRR (95 % CI) 1.4 (1.1-1.6); p < 0.001)]. Use of ITN was associated to malaria protection in the localities [IRR (95 % CI) 0.7 (0.6-0.8); p = 0.001)]. A recurrent P. vivax episode within 90 days was observed in 29.4 % of individuals after an initial diagnosis. A previous P. vivax [IRR (95 % CI) 2.3 (1.3-4.0); p = 0.006)] or mixed P. vivax + P. falciparum [IRR (95 % CI) 2.9 (1.5-5.7); p = 0.002)] infections were significantly associated to a vivax malaria episode within 90 days of follow-up.Conclusions: In an area of P. falciparum and P. vivax co-endemicity, a virtual disappearance of P. falciparum was observed with P. vivax increasing its relative contribution, with a large proportion of recurring episodes. This finding reinforces the perception of P. falciparum being more responsive to early diagnosis and treatment and ITN use and the contribution of relapsing P. vivax to maintain this species' transmission. In areas of P. vivax endemicity, antihypnozoite treatment effectiveness assessment in different transmission intensity may be a fundamental activity for malaria control and elimination.