Department of Tropical Medicine, Bernhard Nocht Institute for Tropical Medicine and I. Department of Medicine University Medical Center Hamburg-Eppendorf, Hamburg, Germany.
German Centre for Infection Research (DZIF), partner site Hamburg-Luebeck-Borstel, Hamburg, Germany.
Clin Microbiol Rev. 2020 Mar 11;33(2). doi: 10.1128/CMR.00104-19. Print 2020 Mar 18.
The continuous increase in long-distance travel and recent large migratory movements have changed the epidemiological characteristics of imported malaria in countries where malaria is not endemic (here termed non-malaria-endemic countries). While malaria was primarily imported to nonendemic countries by returning travelers, the proportion of immigrants from malaria-endemic regions and travelers visiting friends and relatives (VFRs) in malaria-endemic countries has continued to increase. VFRs and immigrants from malaria-endemic countries now make up the majority of malaria patients in many nonendemic countries. Importantly, this group is characterized by various degrees of semi-immunity to malaria, resulting from repeated exposure to infection and a gradual decline of protection as a result of prolonged residence in non-malaria-endemic regions. Most studies indicate an effect of naturally acquired immunity in VFRs, leading to differences in the parasitological features, clinical manifestation, and odds for severe malaria and clinical complications between immune VFRs and nonimmune returning travelers. There are no valid data indicating evidence for differing algorithms for chemoprophylaxis or antimalarial treatment in semi-immune versus nonimmune malaria patients. So far, no robust biomarkers exist that properly reflect anti-parasite or clinical immunity. Until they are found, researchers should rigorously stratify their study results using surrogate markers, such as duration of time spent outside a malaria-endemic country.
长途旅行的持续增加和最近的大规模迁徙改变了非疟疾流行国家（以下称为非流行疟疾国家）输入性疟疾的流行病学特征。虽然疟疾主要是由归国旅行者输入非流行疟疾国家，但来自疟疾流行地区的移民和前往疟疾流行国家探亲访友的旅行者（VFR）的比例持续增加。VFR 和来自疟疾流行国家的移民现在构成了许多非流行疟疾国家大多数疟疾病人的主要组成部分。重要的是，这一组人群具有不同程度的对疟疾的半免疫性，这是由于反复接触感染以及由于长期居住在非疟疾流行地区而导致的保护逐渐下降所致。大多数研究表明，VFR 中存在自然获得性免疫的作用，导致免疫 VFR 和非免疫归国旅行者之间在寄生虫学特征、临床表现以及发生重症疟疾和临床并发症的几率方面存在差异。没有有效的数据表明，对半免疫性和非免疫性疟疾患者的化学预防或抗疟治疗存在不同的方案。到目前为止，还没有可靠的生物标志物可以准确反映抗寄生虫或临床免疫。在找到这些标志物之前，研究人员应该使用替代标志物（例如在疟疾流行国家外停留的时间长短）严格分层他们的研究结果。
