The evolution of virulence in a vector borne disease

特别是在发展中国家，人类直接感受到传染病的影响，即生病，有时甚至死亡。此外，最近的口蹄疫等流行病强调了传染病对发达世界农业的重要性。生态学家也日益认识到，寄生虫在调节许多自然种群和群落方面也很重要。疾病，特别是在一个以上宿主之间共有的疾病，也日益与许多濒危物种的减少有关。因此，我们需要了解为什么寄生虫会造成这样的伤害（毒性）。这个项目将开发一个模型系统，我们可以在其中测试宿主寄生虫进化的许多理论。传染病病原如病毒的生成时间通常比它们的宿主短得多。不仅如此，它们的种群数量庞大，而且由于它们也容易迅速变异，因此在它们的种群中存在巨大的变异潜力。这意味着它们可以在进化过程中迅速变化。已经发展了理论工作，可以预测在各种情况下毒力的变化。这项研究着眼于寄生虫在宿主体内繁殖的速度。高生长速度导致高传播，但也对宿主造成更大的损害，因此毒性更高。从寄生虫和宿主的角度来看，毒力被视为传播增加的不幸副产品。迄今为止，检验这些假设的数据相对较少。本提案的关键目标是使用蜜蜂-螨虫-病毒相互作用作为一个新的模型系统，提供病毒毒力进化理论的第一个经验测试之一。

The effect of infectious diseases is directly felt by humans in terms of illness and sometimes death, in particular in developing countries. Furthermore, recent epidemics such as foot and mouth have emphasized the importance of infectious diseases for agriculture in the developed world. Ecologists are also increasingly realising that parasites are also important in regulating many natural populations and communities. Disease, and in particular disease that is shared between more than one host are also increasingly implicated in the decline of many endangered species. We therefore need to understand why parasites casue the harm (virulence) that they do. This project will develop a model system in which we can test many of the theories of host parasite evolution. Infectious disease agents such as viruses typically have much shorter generation times than their hosts. Not only this they have huge populations and since they also tend to mutate rapidly, there is a vast potential for variation within their populations. This means that they can change rapidly through evolutionary time. Theoretical work has been developed that predicts changes in virulence under a wide range of situations. This work looks at how quickly the parasite reproduces in the host. High growth rate leads to high transmission but also causes more damage to the host and therefore higher virulence. Virulence is seen as an unfortunate by product from the point of view of both the parasite and the host, of increased transmission. As yet there is relatively little data that tests these assumptions. The key goal of this proposal is to use the honeybee-mite-viral interaction as a new model system to provide one of the first empirical tests of the evolutionary theory of viral virulence.