Coadaptation of blood-dwelling apicomplexan parasites and their vertebrate and invertebrate hosts

我的研究重点是血寄生虫和它们的脊椎动物和无脊椎动物宿主之间的相互作用，以研究导致这些寄生虫复杂的生命周期、宿主特异性和毒力的过程。单细胞动物或原生动物中最重要的类群之一是顶复合体门。这一门的寄生虫引起许多毁灭性的疾病，包括人类的疟疾和弓形虫病，以及家畜的球虫病和新孢子病。此外，几乎每一种野生动物的血液、组织或肠道中都寄生着一些顶复合体寄生虫。我的建议的目的是确定功能，免疫学，生态学和系统发育特征与吸血顶端复合体寄生虫和脊椎动物和无脊椎动物宿主细胞之间的相互作用有关。我提出了一种多样化的研究方法，使用两个定义良好的模型系统来辨别形成顶复合体寄生虫和宿主之间相互作用基础的机制。第一个系统涉及肝虫属的两种血液寄生虫，即肝虫和猫肝虫，它们通过吸血蚊子在绿蛙和牛蛙之间传播。第二个系统的特点是另一种物种——sipedon肝虫（Hepatozoon sipedon），它会传播给以蛇血为食的蚊子，然后再传播给以受感染蚊子为食的青蛙。以被感染的青蛙为食的蛇完成了这个循环。*** *******我的学生和我感兴趣的是，与人类疟疾寄生虫有关的肝虫寄生虫如何受到耐寒和对冷冻敏感的青蛙物种的温度的影响，以及它们如何调节它们在青蛙和蛇中的发育，以便它们最大限度地传播给蚊子，同时确保它们不会杀死任何宿主。然而，在青蛙和蛇的血液中经常观察到严重的感染，尽管这些宿主似乎没有受到不利影响，但这种感染会杀死蚊子。我们建议通过研究这种蚊子的免疫反应或缺乏免疫反应来确定这种病理的原因。我们还计划研究哪些种类的蚊子、青蛙和蛇是这些肝虫寄生虫的合适宿主，以及抗性宿主如何在寄生虫生命周期的不同阶段消灭这些原生动物。这些研究将有助于确定这些寄生虫的生态作用，并有助于制定新的控制措施，以防止在加拿大和其他地方传播西尼罗病毒和其他病原体的蚊子种类。这项研究还将评估这些寄生虫是否会在加拿大脆弱的青蛙种群中引起疾病，并确定这些寄生虫与更致命的病原体（如Ranavirus和壶菌）之间的关系，这些病原体已经摧毁了加拿大和世界其他地区的青蛙种群

My research focuses on the interactions between blood parasites and their vertebrate and invertebrate hosts to investigate the processes that result in the complex life cycles, host specificity and virulence of these parasites.  One of the most important groups of one-celled animals, or protozoa, is the phylum Apicomplexa.  Parasites in this phylum cause many devastating diseases, including malaria and toxoplasmosis of humans, and coccidiosis and neosporosis of domesticated animals.  Additionally, nearly every species of wildlife is parasitised with a number of apicomplexan parasites in their blood, tissues or intestinal tracts.  The aim of my proposal is to identify the functional, immunological, ecological and phylogenetic features associated with the interaction between blood-dwelling apicomplexan parasites and vertebrate and invertebrate host cells.  I propose a diverse research approach using two well-defined model systems that will discern mechanisms forming the basis of interactions between apicomplexan parasites and hosts. The first system involves two blood parasites of the genus Hepatozoon, namely Hepatozoon clamatae and Hepatozoon catesbianae, which are transmitted among green frogs and bullfrogs by blood-feeding mosquitoes.  The second system features another species, Hepatozoon sipedon, which is passed to mosquitoes that feed on snake blood, and then to frogs that feed on infected mosquitoes. Snakes that feed on infected frogs complete the cycle.*** *******My students and I are interested in how Hepatozoon parasites, which are related to human malaria parasites, are influenced by temperatures in freeze-tolerant and freeze-sensitive frog species, and how they modulate their development in frogs and snakes so that they maximise transmission to mosquitoes, while at the same time ensuring that they do not kill any of their hosts.  However, heavy infections are frequently observed in the blood of frogs and snakes, and although these hosts appear not to be adversely affected, such infections will kill mosquitoes.  We propose to determine the cause of this pathology by investigating the immune response, or lack thereof, in such mosquitoes. We also plan to investigate which species of mosquitoes, frogs and snakes are suitable hosts for these Hepatozoon parasites, and how resistant hosts eliminate these protozoa at different stages of the parasite life cycle.  Such studies will be useful for determining the ecological role of these parasites, and for developing novel control measures against species of mosquitoes that transmit West Nile Virus and other pathogens in Canada and elsewhere.  This research will also assess if these parasites cause disease in vulnerable frog populations in Canada, and ascertain the relationship between these parasites and more virulent pathogens, such as Ranavirus and chytrid fungi, that have devastated frog populations in Canada and other parts of the world.***