An integrated approach to tackling drug resistance in livestock trypanosomes.

耐药性是世界上许多疾病日益严重的问题。锥虫是采采蝇传播的单细胞生物，在牛中引起严重疾病——非洲动物锥虫病（AAT），主要发生在撒哈拉以南非洲，那里大约有6 000万头牛处于危险之中，AAT每年导致300万头牛死亡。农民对抗AAT的主要措施是药物治疗，但我们只有两种主要药物，这两种药物都有50多年的历史，而且被广泛使用。对这些药物的耐药性的报道越来越多，而且正在开发的药物很少，这意味着目前的控制方法的可持续性非常值得怀疑。尽管这是一个如此重要的问题，但我们对锥虫如何抵抗药物的作用以及AAT耐药性如何出现和传播知之甚少。因此，我们部署明智策略来缓解问题的能力有限。该项目旨在生成数据和资源，以弥合这些知识差距。自2011年以来，申请人一直在坦桑尼亚北部的一个地区工作。最近，农民报告药物治疗失败，需要更频繁地使用越来越多的预防性药物氯异异胺（ISM），这表明出现了耐药性。我们已经从2011年至2017年采样的该地区的一系列农场获得了5000头牛和10000只采采蝇的样本，以及农民吸毒的信息。此外，我们已经开发了在实验室中研究相关锥虫物种刚果锥虫的资源和能力（大多数信息来自人类感染的布鲁氏锥虫，但越来越明显的是，这些是非常不同的生物体）。这个初步数据和资源平台将用于回答我们的中心假设，即坦桑尼亚动物锥虫病的管理受到ISM未能提供充分预防的威胁。为了验证这一假设，我们将解决四个主要的研究问题：(i)对ISM产生抗性的可能机制是什么，我们能否确定一个标记？ISM失效的程度和原因是什么？（iii） ISM失败的流行病学后果是什么？（四）如何预防对锥虫的抗药性，包括新药？为了实现这一目标，我们将：(1)通过在实验室中产生耐药寄生虫，并使用生化、分子和基因组分析比较耐药和易感寄生虫，从而确定ISM的耐药机制；(2)收集同一地区的现场资料，进行用药和药品质量评价，分离耐药寄生虫，评估现场用药和耐药流行病学情况；(3)利用实验室和现场数据相结合，生成一个数学模型，其参数由实验室和现场数据提供信息，使我们能够准确评估田间AAT的抗性如何产生和传播；(4)应用该模型并预测将为我们的工业合作伙伴GALVmed正在开发的一种新的锥虫化合物的选择和耐药性传播提供信息的情景。该项目的成果将为AAT耐药流行病学提供前所未有的详细见解，揭示与疾病相关的锥虫物种（包括潜在标记物）的耐药机制，并将开发数学模型的首次应用，重要的是使用准确的参数，以提供对AAT耐药出现和传播动态的见解。除了提供新的见解外，这些产出还可能通过确定最有可能减轻耐药性的战略，从而最大限度地延长现有药物和新药的使用寿命，从而为药物开发和药物使用提供信息。

Drug resistance is an increasing problem for many diseases worldwide. Trypanosomes are tsetse-fly transmitted single-celled organisms that cause serious disease in cattle - African Animal Trypanosomiasis (AAT), mainly in sub-Saharan Africa, where approximately 60 million cattle are at risk and AAT kills 3 million each year. The main measure farmers have to combat AAT is drug treatment, but we only have two main drugs, both of which are >50 years old and widely used. Resistance to these drugs is increasingly reported, and there are very few drugs in the development pipeline, meaning the current control methods have very doubtful sustainability. Despite being such a significant issue, we know very little about how trypanosomes resist the effect of the drug, and how AAT drug resistance emerges and spreads. Therefore we are limited in our ability to deploy informed strategies to mitigate the problem. This project aims to generate data and resources to bridge these knowledge gaps. The applicants have been working in an area in Northern Tanzania since 2011. Recently farmers have been reporting drug treatment failure and the need to use increasing amounts of the prophylactic drug Isometamidium chloride (ISM) more frequently, suggesting emerging resistance.We already have samples from 5,000 cattle and 10,000 tsetse flies, as well as information on farmer drug use, from a cohort of farms in the area sampled between 2011 and 2017. Additionally, we have developed resources and capabilities for working on the relevant trypanosome species, Trypanosoma congolense, in the laboratory (most information derives from the human-infective Trypanosoma brucei, but it is increasingly apparent that these are very distinct organisms). This platform of preliminary data and resources will be used to answer our central hypothesis, that the management of animal trypanosomiasis in Tanzania is threatened by an emerging failure of ISM to provide adequate prophylaxis. To test this hypothesis, we will address four main research questions: (i) what are the likely mechanisms by which resistance to ISM occurs and can we identify a marker?; (ii) what are the extent and cause of ISM failure?; (iii) what are the epidemiological consequences of ISM failure?; and (iv) how might resistance to trypanocides, including new drugs, be prevented? To achieve this we will: (1) identify ISM resistance mechanisms by generating resistant parasites in the laboratory and comparing resistant and susceptible parasites using biochemical, molecular and genomic analysis; (2) collect field data in the same area in order to assess drug use and drug quality, isolate drug resistant parasites, and assess the epidemiology of drug use and drug resistance in the field; (3) using data combined from the laboratory and the field, generate a mathematical model whose parameters are informed by both the laboratory and field data, allowing us to accurately assess how resistance emerges and spreads in AAT in the field; and (4) apply the model and predict scenarios that will inform on the selection and spread of resistance for a new trypanocidal compound in development by our industrial partners, GALVmed. The outputs of this project would provide unprecedented and detailed insight into the epidemiology of AAT drug resistance, uncover mechanisms of drug resistance in the disease-relevant trypanosome species (including potential markers), and will develop the first application of mathematical modelling, importantly using accurate parameters, to provide insights into the dynamics of AAT drug resistance emergence and spread. As well as providing novel insights, the outputs have the potential to inform drug development and drug usage, by identifying strategies that will have the best chances of mitigating resistance, and therefore maximising the lifetime of both existing and novel drugs.