A systems biology approach to infectious disease transmission: linking individuals populations and ecosystems

你有没有想过（或者希望）蚊子会咬你的狗而不是你？生态学理论告诉我们，动物应该进化为专门的饮食，以最大限度地提高它们的生存和繁殖。以吸血昆虫为例，这种进化可以解释为什么有些物种只咬人类，而另一些物种更喜欢家养或野生动物。有证据表明，大多数吸血昆虫的生存和繁殖，包括蚊子、臭虫、跳蚤和咬人的苍蝇，取决于它们所咬的脊椎动物的种类。这些昆虫体内寄生虫的生存也受到脊椎动物物种选择的影响，其中许多寄生虫会引起人类和动物的严重疾病；一些动物的血液促进了寄生虫的生长，而另一些动物的血液则阻止了寄生虫的生长。在这种情况下，如果供吸血昆虫使用的动物宿主范围突然在景观尺度上发生变化，会发生什么？这种变化将如何影响人类和动物疾病的传播？这一实验发生在自然界，随着人口的增长，供吸血昆虫食用的动物种类正在迅速变化；减少其他脊椎动物的可用性，有利于他们自己和他们的牲畜。脊椎动物物种选择的缩小对下游的影响尚不清楚；特别是它将如何影响生物多样性和叮咬昆虫的数量，以及它们所携带疾病的传播。了解这些脊椎动物宿主物种组成的变化如何影响叮咬昆虫的生存、种群增长和寄生虫传播潜力是本项目的中心目标。利用这些信息来制定和测试数学模型，预测昆虫数量和疾病风险将如何随着人类引起的特定土地利用变化而变化，这是我的最终目标。非洲是世界上最致命的虫媒疾病肆虐的大陆；土地使用方式开始发生变化。大规模城市化和集约化农业发展目前还不普遍，但在未来十年内将越来越普遍。因此，在这里，研究脊椎动物物种多样性对吸血昆虫的影响比在任何地方都更有可能为解决与土地利用变化相关的有害生态和流行病学后果提供先发制人的解决方案。我将进行一系列新颖的实验室分析、生物学上现实的行为分析和密集的实地收集，以测试非洲常见的冈比亚按蚊（Anopheles gambiae s.s.）和冈比亚按蚊（Anopheles gambiae s.s.）的生存和繁殖。相对于次要宿主物种（山羊、鸡和狗），Arabiensis受其更喜欢的宿主物种（人类和牛）的可用性的影响。我将测试这两种蚊子相互竞争的能力是否取决于它们偏好的宿主物种（人类为蚊子）的相对丰度。冈比亚，和牛为安。arabiensis)。最后，我将调查这些蚊子体内疟疾寄生虫的发展是否受到它们被感染时所摄入的血液类型（人、牛、山羊、鸡或狗）的影响。在实验中收集的信息将用于制定蚊子和寄生虫种群增长作为宿主物种组成函数的数学模型。我将使用这个模型来研究脊椎动物宿主的组成如何向人类倾斜（如城市化所预期的那样），或向牲畜和人类混合（如农业扩张所预期的那样），将影响蚊子的丰度、生物多样性和疟疾传播强度。最后，这些模型将适用于东非疟疾流行地区的实际景观，以预测当前和预测的土地利用活动变化如何影响按蚊种群动态和人类健康。

Did you ever wonder (and wish) that mosquitoes would bite your dog instead of you? Ecological theory tells us that animals should evolve to specialize on diets that most increase their survival and reproduction. In the case of blood-feeding insects, this evolution may explain why some species bite only humans, whereas others prefer domesticated or wild animals. Evidence shows that the survival and reproduction of most blood-feeding insects, including mosquitoes, bed bugs, fleas, and biting flies, depends on the species of vertebrate that they bite. The survival of parasites within these insects, many of whom cause severe disease in humans and animals, is also influenced by vertebrate species choice; with the blood of some animals enhancing parasite growth, and others blocking it. Given this is the case, what would happen if the range of animal hosts available to blood-feeding insects was suddenly changed on a landscape scale, and how would this change impact the spread of human and animal disease? This experiment is occurring in nature, where the variety of animal species available to blood-feeding insects is rapidly changing as human populations expand; reducing the availability of other vertebrates in favour of themselves and their livestock. The downstream impacts of this narrowing of vertebrate species choice are not yet known; particularly with respect to how it will impact the biodiversity and abundance of biting insects, and the spread of the diseases they carry. Understanding how these changes in vertebrate host species composition influence the survival, population growth and parasite transmission potential of biting insects is the central aim of this project. Using this information to formulate and test mathematical models that predict how insect abundance and disease risk will change in response to specific human-induced land-use changes is my ultimate goal. In Africa, a continent inflicted by the world's deadliest insect-borne diseases; changes in land-use practices are starting to take place. Large-scale urbanization and intensive agricultural development are not yet common, but will become increasingly so within the next decade. Thus here more than anywhere, study of the impact of vertebrate species diversity on blood-feeding insects has the potential to provide pre-emptive solutions to detrimental ecological and epidemiological consequences associated with changes in land use. I will conduct a series of novel laboratory analyses, biologically realistic behavioural assays, and intensive field collections in order to test whether the survival and reproduction of the common African mosquitoes Anopheles gambiae s.s. and An. arabiensis is influenced by the availability of host species that they prefer (humans and cows) relative to those that are secondary (goats, chickens and dogs). I will test whether the ability of these two mosquito species to compete with one another is determined by the relative abundance of their preferred host species (humans for An. gambiae, and cows for An. arabiensis). Finally I will investigate whether the development of malaria parasites within these mosquitoes is influenced by the type of blood (human, cow, goat, chicken or dog) that they consume when they are infected. Information gathered in the experiments will be used to formulate a mathematical model of mosquito and parasite population growth as a function of host species composition. I will use this model to examine how skewing the composition of vertebrate hosts towards humans (as expected under urbanization), or to a mixture of livestock and humans (as expected under agricultural expansion) will influence mosquito abundance, biodiversity, and malaria transmission intensity. Finally, these models will be fit to actual landscapes within a malaria-endemic region of east Africa to predict how current and forecasted changes in land-use activities could impact Anopheline population dynamics and human health.