STRESS-MALAWI: Strengthening Resilience against Sleeping Sickness in Malawi

预测、发现和应对已知和新发传染病的暴发是一个世界性问题，特别是在卫生系统脆弱的国家。在撒哈拉以南非洲，已发生和新出现的人畜共患疾病（例如埃博拉）暴发往往起源于偏远的荒野地区，在那里，病原体在野生宿主之间传播，基本上未被发现，人间病例很少。由于尚不清楚的原因，这些病原体的传播动态可能发生变化，并随着疾病外溢到邻近人群和牲畜中而发生疫情。罗得西亚人类非洲锥虫病（rHAT）由采采蝇传播的布氏罗得西亚锥虫病引起，是一种与东非和南部非洲保护区有关的人畜共患疾病。2019- 2020年，马拉维的rHAT病例激增。在短短三个月的时间里，病例数量是前十年年平均数量的三倍，其中大多数病例来自两个国家公园附近的社区。疫情激增的根本原因尚不确定，但潜在原因包括环境变化导致采采蝇的生态和行为发生变化，和/或出现了一种强毒的布氏罗得西亚锥虫菌株。目前，马拉维对rHAT的控制主要依赖于被动发现和治疗病例。没有疫苗或药物可以预防rHAT，保护人们的唯一方法是控制采采蝇，然而，在国家公园里这样做是非常昂贵的，后勤也很复杂。需要更经济和可持续的策略，将采采蝇从定居区域移除，并将其限制在公园内。STRESS-MALAWI项目的总体目标是测试这样一个假设，即生活在保护区边缘的社区发生rHAT的风险可以通过将采采蝇控制工作集中在维持采采蝇种群叮咬人类的关键生态区来降低。这些区域很可能是保护区的边缘，在那里茂密的自然植被和丰富的野生寄主维持着相对靠近定居点的大量采采蝇。我们将重点关注马拉维北部的Vwaza沼泽野生动物保护区及周边农业区，开展实证和建模研究，量化rHAT的潜在时空驱动因素，并确定2019年病例激增的潜在原因。这些研究的结果将使我们能够设计和提供具有成本效益和空间信息的采采蝇控制战略，其中将部署吸引和杀死采采蝇的经杀虫剂处理的目标，以保护社区免受rHAT的侵害。为了实现我们的目标，我们将：-首先，制定和实施采采蝇取样策略，以量化采采蝇和锥虫在保护区和农业区的种群动态。采采蝇将沿着界面的横断面进行采样，同时使用卫星和无人机图像对土地覆盖进行测绘，将量化采采蝇丰度与植被之间的关系。其次，量化被户外和建筑物内活动的人吸引的采采蝇的数量和类型，从而确定人们可能被叮咬的地点和时间。第三，确定罗得西亚锥虫的传播潜力是否因出现新的毒力强的寄生虫菌株而增加。最后，我们将整合1-3的知识，在Vwaza沼泽保护区的界面设计和实施矢量控制策略。我们的研究结果将有助于在马拉维和东非和南部非洲的其他国家制定监测和控制rHAT的战略。更广泛地说，我们项目产生的数据、模型、锥虫基因组和方法将有助于制定以证据为基础的战略，以控制与荒野地区有关的现有和新出现的媒介传播的人畜共患病。

Predicting, detecting and responding to outbreaks of known and emerging infectious diseases pose a worldwide problem, particularly in countries where the health system is fragile. In sub-Saharan Africa, outbreaks of established and emerging (e.g. Ebola) zoonotic diseases often have their origins in remote wilderness areas where pathogens circulate largely undetected between wild reservoir hosts and with few human cases. For reasons poorly understood, the transmission dynamics of these pathogens can change and outbreaks occur as the disease spills over into neighbouring populations of humans and livestock.Rhodesian Human African Trypanosomiasis (rHAT), caused by Trypanosoma brucei rhodesiense transmitted by tsetse flies, is a zoonotic disease associated with conservation areas of East and Southern Africa. In 2019-20, Malawi experienced a surge of rHAT cases. In a period of just three months, the number of cases was triple the annual mean for the previous decade, with most cases coming from communities located near two national parks. The underlying causes of the surge are uncertain but potential causes include changes in the ecology and behaviour of tsetse as a consequence of environmental changes, and/or the emergence of a virulent strain of Trypanosoma brucei rhodesiense. Currently, control of rHAT in Malawi relies largely on passive detection and treatment of cases. There are no vaccines or drugs to prevent rHAT and the only way of protecting people is by controlling tsetse flies, however, to do this across a national park is prohibitively expensive and logistically complex. More affordable and sustainable strategies which remove tsetse from settled areas and confine them to the park are needed.The overall goal of the STRESS-MALAWI project is to test the hypothesis that risk of rHAT for communities living on the edge of conservation areas can be reduced by focusing tsetse control efforts on the key ecological zones which sustain the tsetse populations biting humans. These zones are likely to be the edges of a conservation area where dense natural vegetation and an abundance of wild hosts sustain high numbers of tsetse relatively close to settlements.Focusing on the Vwaza Marsh Wildlife Reserve in northern Malawi, and the surrounding farming areas, we will undertake empirical and modelling studies to quantify the underlying spatial and temporal drivers of rHAT and identify potential causes of the 2019-surge in cases. Findings from these studies will allow us to design and deliver a cost-effective and spatially-informed tsetse control strategy in which insecticide-treated targets, which attract and kill tsetse, will be deployed to protect communities from rHAT. To achieve our goal, we will:-First, develop and implement a tsetse sampling strategy to quantify the population dynamics of tsetse and trypanosomes across the interface of conservation and agricultural areas. Tsetse will be sampled along transects across the interface and simultaneous mapping of landcover using satellite and drone imagery will quantify the relationship between tsetse abundance and vegetation.Second, quantify the numbers and type of tsetse attracted to humans moving outdoors and within buildings and hence identify where and when people are likely to be bitten.Third, determine whether the transmission potential of T. b. rhodesiense has increased due to the emergence of a new virulent strain of parasite.Finally, we will integrate knowledge from 1-3 to design and implement a vector control strategy at the interface of the Vwaza Marsh Reserve.Our findings will contribute to the development of a strategy for monitoring and control of rHAT in Malawi and other countries in East and Southern Africa. More generally, the data, models, trypanosome genomes and methods produced by our project will contribute to evidence-based strategies for controlling existing and emerging vector-borne zoonoses associated with wilderness areas.