Maladies Infectieuses et Vecteurs: Ecologie, Génétique, Evolution et Contrôle (MIVEGEC), UMR CNRS 5290-IRD 224-UM1-UM2, Montpellier, France; Centre d'Ecologie Fonctionnelle et Evolutive (CEFE), UMR CNRS 5175, Montpellier, France.
J Anim Ecol. 2014 Jan;83(1):256-65. doi: 10.1111/1365-2656.12113. Epub 2013 Aug 8.
Host resources can drive the optimal parasite exploitation strategy by offering a good or a poor environment to pathogens. Hosts living in resource-rich habitats might offer a favourable environment to developing parasites because they provide a wealth of resources. However, hosts living in resource-rich habitats might afford a higher investment into costly immune defences providing an effective barrier against infection. Understanding how parasites can adapt to hosts living in habitats of different quality is a major challenge in the light of the current human-driven environmental changes. We studied the role of nutritional resources as a source of phenotypic variation in host exploitation by the avian malaria parasite Plasmodium relictum. We investigated how the nutritional status of birds altered parasite within-host dynamics and virulence, and how the interaction between past and current environments experienced by the parasite accounts for the variation in the infection dynamics. Experimentally infected canaries were allocated to control or supplemented diets. Plasmodium parasites experiencing the two different environments were subsequently transmitted in a full-factorial design to new hosts reared under similar control or supplemented diets. Food supplementation was effective since supplemented hosts gained body mass during a 15-day period that preceded the infection. Host nutrition had strong effects on infection dynamics and parasite virulence. Overall, parasites were more successful in control nonsupplemented birds, reaching larger population sizes and producing more sexual (transmissible) stages. However, supplemented hosts paid a higher cost of infection, and when keeping parasitaemia constant, they had lower haematocrit than control hosts. Parasites grown on control hosts were better able to exploit the subsequent hosts since they reached higher parasitaemia than parasites originating from supplemented hosts. They were also more virulent since they induced higher mass and haematocrit loss. Our study highlights that parasite virulence can be shaped by the host nutritional status and that parasite can adapt to the environment provided by their hosts, possibly through genetic selection.
宿主资源可以通过为病原体提供良好或恶劣的环境来驱动最佳的寄生虫利用策略。生活在资源丰富的栖息地的宿主可能为寄生虫的发育提供有利的环境，因为它们提供了丰富的资源。然而，生活在资源丰富的栖息地的宿主可能会投入更多的成本来进行昂贵的免疫防御，从而为感染提供有效的屏障。了解寄生虫如何适应生活在不同质量栖息地的宿主是当前人类驱动的环境变化背景下的主要挑战。我们研究了营养资源作为宿主利用的表型变异的来源，以鸟类疟原虫 Plasmodium relictum 为研究对象。我们调查了鸟类的营养状况如何改变寄生虫在宿主体内的动态和毒力，以及寄生虫经历的过去和当前环境之间的相互作用如何解释感染动态的变化。实验感染的金丝雀被分配到对照组或补充饮食组。在随后的实验中，经历了两种不同环境的 Plasmodium 寄生虫通过全因子设计被传播到新的宿主身上，这些新的宿主在类似的对照或补充饮食下饲养。食物补充是有效的，因为补充饮食的宿主在感染前的 15 天内体重增加。宿主营养对感染动态和寄生虫毒力有强烈的影响。总的来说，寄生虫在控制组（非补充饮食）的鸟类中更成功，达到更大的种群规模，并产生更多的有性（可传播）阶段。然而，补充饮食的宿主感染成本更高，当保持相同的寄生虫血症时，它们的红细胞压积比对照组的宿主低。在对照组宿主上生长的寄生虫能够更好地利用随后的宿主，因为它们达到的寄生虫血症比来自补充饮食的宿主的寄生虫更高。它们也更具毒性，因为它们导致更高的体重和红细胞压积损失。我们的研究强调了寄生虫的毒力可以被宿主的营养状况塑造，并且寄生虫可以通过遗传选择来适应宿主提供的环境。
