The genetic basis of host resistance / susceptibility to parasite infection in a wild vertebrate population: a pilot study.

所有自然种群的动物都感染了病原体和寄生虫：这是“正常”的状态。由于这种寄生虫非常常见，它们是自然种群中的重要力量。动物在面对寄生虫时并不被动--它们会产生免疫反应，试图保护自己。但是，我们对寄生虫感染在大多数野生种群中的表现知之甚少。我们也不真正理解为什么有些动物会严重感染，而另一些动物几乎没有感染。我们建议在回答这些问题方面迈出第一步。要做到这一点，我们将研究一个野生种群的青蛙（非洲爪蟾），这是常见的感染蠕虫（Protopolystoma xenopodis）在其膀胱。我们正在使用对这种青蛙的野生种群进行的长达25年的研究结果，许多动物在其一生中一直受到关注。重要的是，对于这些动物，我们知道他们有多少蠕虫。这些结果已经告诉我们，这些青蛙可以产生良好的免疫反应，使它们免受蠕虫的侵害。但是，有一些动物总是被蠕虫感染，有些动物偶尔会被感染。所以，不同的个体在攻击这些蠕虫方面有不同的表现。我们认为，造成动物之间这些差异的原因是它们控制免疫系统如何工作的基因。我们将通过比较不同动物的这些基因，特别是比较从未感染蠕虫的动物和总是感染蠕虫的动物，来看看这是否正确。我们有兴趣这样做的更大原因是为了了解为什么不同的个体动物在不同种类的感染（例如病毒，细菌，真菌，蠕虫）方面存在差异。通过发现这一点，我们可以开始研究现有的感染（或未来的新感染）如何影响野生种群。随着地球气候的变化，这一点尤其重要，因为这使动物面临着前所未有的感染。目前两栖动物感染壶菌可能已经是一个例子。

All natural populations of animals are infected with pathogens and parasites: this is the 'normal' state-of-affairs. Because such parasites are so common, they are an important force in natural populations. Animals are not passive in the face of parasites - they generate immune responses to try and protect themselves. But, we know rather little about how parasite infections behave in most wild populations. We also do not really understand how and why some animals have heavy infections, while others are hardly infected at all. We are proposing to take a first step in answering these questions. To do this we will study a wild population of frogs (Xenopus laevis) that is commonly infected by a worm (Protopolystoma xenopodis) in its bladder. We are using the results of an approximately 25 year-long study of a wild population of this frog, for which many animals have been followed throughout their lives. Importantly, for these animals we know how many worms they have had. These results have already told us that these frogs can make good immune responses that keep them free of worms. But, there are a number of animals who are always infected with worms, and some who occasionally become infected. So, different individuals vary in how good they are at attacking these worms. We think that what is causing these differences between animals is the genes they have that control how their immune system works. We are going to see if this is correct by comparing these genes in different animals, particularly comparing animals who never have worm infections with animals that always have worm infections. The bigger reason why we are interested in doing this is to understand why different individual animals vary in what different sorts of infections (e.g. virus, bacteria, fungus, worms) they have. By discovering this, we can then begin to work out how existing infections (or new infections in the future) might affect wild populations. This is especially important as the planet's climate is changing, because this is exposing animals to infections they have not seen before. The current infection of amphibians with chytrid fungus might be an example of this already.