亚马逊的人类流动性“将疟疾推向城市”

疟疾has traditionally been seen as a rural scourge, but increasingly it is being documented in or near urban areas, experts warn, as a new study shows that human mobility plays an important role in the “urbanisation” of the disease.

该研究旨在找出如何Plasmodiumparasite, which transmits the disease through the按蚊mosquito, enters urban areas. Over a four-year period, researchers tracked human mobility patterns from rural settlements to Mâncio Lima, a city of 17,000 inhabitants in the Brazilian state of Acre, near the border with Peru, and the main urban malaria hotspot of Brazil.

MâncioLima曾是一个“实验室”，研究人员和地方当局可以在其中关注人类流动性与疟疾之间的关系。像其他水域城市一样，它的寄生虫年龄很高，媒介的存在按蚊in the city centre, and a constant flow of human traffic between the urban, rural and peripheral areas.

结果可能会帮助其他16个亚马逊市，占该国恶性疟疾的80％，甚至可以防止在诸如朗多尼亚州首都波尔托·维洛（Porto Velho）等城市爆发该疾病，而马纳斯（Manaus）和亚马纳纳州的首都马纳斯（Manaus）。

在2016年至2019年之间，该小组每六个月进行一次家庭调查，涉及该市20％的房屋和2,000人。

作者写道：“我们发现，城市居民最常访问的农村地区通常是疟疾传播最强烈的农村地区。”paper出版于Plos One。

该研究指出：“这些地区还贡献了在市区诊断出的绝大多数进口疟疾感染。”

在巴西亚马逊的人造养鱼池塘广泛是疟疾媒介蚊子的繁殖地。图片来源：CortesíaDeIgor。

官方数字表明99 per cent在该国记录的所有病例中，亚马逊都集中在亚马逊上，这也发现恶性疟疾的发病率增加，这是寄生虫造成的最严重的疾病形式恶性疟原虫。Seventeen out of 807 riverside cities (2 per cent) contribute to 80 per cent of this type of malaria.

Igor Cavallini Johansen, a researcher at the Institute of Biomedical Sciences of the University of São Paulo and lead author of the study, explains that almost 20 per cent of families in Mâncio Lima maintain both urban and rural residences.

最常见的目的地是两个小型农村定居点，名为Tonico和Timbauba。虽然MâncioLima镇的平均年度寄生虫发生率为每年1,000人口442例，而这本身对于城市环境来说本身很高，但访问量最高的地区的Tonico在该地区发病率最高，估计为1,714例。1,000名居民，暴露游客有实质性的疟疾风险。

“这个外围人在大部分时间里花费大部分时间，正是发病率更高的地方。”SciDev.Net。

“If surveillance and control actions are not efficient, mobility increases exposure to risk of infection and transmissibility”

Claudio Ribeiro, head of malaria research laboratory, Oswaldo Cruz Institute

Mosquitoes are abundant in Mâncio Lima and can sustain local malaria transmission because of the unplanned peri-urban spaces near forested areas and the widespread artificial fish-farming ponds. “So, we have the按蚊— the vector which is dispersed throughout the city — and we have the parasite,” added Johansen.

Researchers emphasise that people travel from urban to rural areas as a means of survival: they cultivate the land in peri-urban agricultural settlements, where they need to stay overnight, and return to the city to sell their products and access services such as schools and healthcare.

MâncioLima20公里以内的地区占通宵隔夜的58％，这一数字尤其重要按蚊mosquito is nocturnal. Research also found that most mobile urban residents are typically poor males aged 16 to 60 years old from multi-sited households who lack a formal job.

免疫学家克劳迪奥·里贝罗,head of the Malaria Research Laboratory at Oswaldo Cruz Institute (IOC/Fiocruz), who wasn’t involved in the study, tellsSciDev.Net：“如果监视和控制动作不是有效的，那么流动性会增加感染和传播性的风险。”

这些结果还排除了一个普遍接受的想法，即传播更强烈的社区（可能会驱动大多数城市疟疾风险）是难以到达的河流村庄。

Ribeiro说：“这有助于解构我们只在孤立社区中疟疾的想法。”

经过十年的衰落，疟疾显示53％随着健康投资的下降，2017年在巴西。

“If the lack of investment in health — combined with these mobility patterns — continues and malaria reaches populous urban centres, the consequences might be devastating,” Johansen warns.

为了避免这样的结果，作者建议“减少移动性，找到这些流动人士，将诊断扩展到城市中心和农村地区的治疗中，并提高这些地区的服务质量”。

Ribeiro urges public authorities of the 38 Amazonian municipalities that account for 80 per cent of malaria in Brazil to “improve surveillance and control actions”.

This piece was produced by SciDev.Net’s Latin America & Caribbean desk.

The study was supported by FAPESP, a SciDev.Net donor.