The impact of imported malaria by gold miners in Roraima: characterizing the spatial dynamics of autochthonous and imported malaria in an urban region of Boa Vista

BACKGROUND The number of malaria cases in Roraima nearly tripled from 2016 to 2018. The capital, Boa Vista, considered a low-risk area for malaria transmission, reported an increasing number of autochthonous and imported cases. OBJECTIVES This study describes a spatial analysis on malaria cases in an urban region of Boa Vista, which sought to identify the autochthonous and imported cases and associated them with Anopheles habitats and the potential risk of local transmission. METHODS In a cross-sectional study at the Polyclinic Cosme e Silva, 520 individuals were interviewed and diagnosed with malaria by microscopic examination. Using a global positional system, the locations of malaria cases by type and origin and the breeding sites of anopheline vectors were mapped and the risk of malaria transmission was evaluated by spatial point pattern analysis. FINDINGS Malaria was detected in 57.5% of the individuals and there was a disproportionate number of imported cases (90.6%) linked to Brazilian coming from gold mining sites in Venezuela and Guyana. MAIN CONCLUSIONS The increase in imported malaria cases circulating in the west region of Boa Vista, where there are positive breeding sites for the main vectors, may represent a potential condition for increased autochthonous malaria transmission in this space.

【背景】2016年至2018年，巴西罗赖马州（Roraima）的疟疾病例数近乎增至三倍。该州首府博阿维斯塔（Boa Vista）曾被视为疟疾传播低风险区域，但其报告的本地感染病例与输入性病例数量均呈上升趋势。
【研究目的】本研究针对博阿维斯塔城区的疟疾病例开展空间分析，旨在甄别本地感染与输入性疟疾病例，并将其与按蚊（Anopheles）孳生环境及本地疟疾传播潜在风险进行关联。
【研究方法】本研究在科斯梅·埃·席尔瓦综合诊所（Polyclinic Cosme e Silva）开展横断面研究，共访谈520名受访者，并通过显微镜检查确诊疟疾。借助全球定位系统（Global Positioning System），研究人员绘制了按类型与来源分类的疟疾病例位置，以及按蚊媒介孳生位点的分布地图，并通过空间点模式分析评估了疟疾传播风险。
【研究结果】57.5%的受访者检测出疟原虫感染；其中输入性病例占比达90.6%，此类病例多与曾前往委内瑞拉与圭亚那金矿作业的巴西人员相关，占比失衡显著。
【主要结论】博阿维斯塔西部地区存在主要媒介按蚊的阳性孳生位点，而该区域内输入性疟疾病例的传播扩散，可能成为本区域本地疟疾传播风险升高的潜在诱因。