Ecology of host/parasite interactions

所有寄生虫都必须解决将感染阶段传播到新宿主的问题。毫不奇怪，“传播率”是描述寄生虫种群动态的流行病学模型中的一个基本参数，包括人类、家畜和野生动物的问题寄生虫。我的研究计划的长期目标是了解决定野生动物寄生虫传播率变化的因素。*许多寄生虫具有复杂的生命周期，其完成需要在一系列专属宿主之间传播感染阶段。一些解决主机之间传播问题的解决方案在表达上是壮观的。感染了吸虫幼虫的蚂蚁被司机从它们的巢穴送到邻近的花朵上，晚上它们仍然与它们的下颌附着在一起。当第二天气温回暖时，它们就会分离并返回巢中。附着有助于幼虫向食草性哺乳动物的传播。这种依附/脱离的循环在我们位于艾伯塔省柏树山公园的研究地点持续了数周，在那里引入了吸虫。在这个提案中，我和我的学生结合了基因组学工具、成像工具和行为分析，以确定僵尸是否需要对大脑中控制下颌肌肉的结构进行物理操作，或者需要分泌导致神经调节的基因产物，或者两者兼而有之。一种可能性是，附着/脱离行为与特定基因产物的上调有关，这些基因产物与温度有关。了解导致感染蚂蚁附着/脱离循环的机制是了解寄生虫引起宿主表型改变的普遍现象的关键一步，这种现象延伸到感染弓形虫的人和感染狂犬病病毒的野生动物/宠物。*在第二个模型系统中，我们操纵感染剂量来测试有关寄生虫传播率变化的因素的假设。我和我的学生将评估宿主社区的多样性和结构如何影响传播率。在我们这个动物生物多样性不断变化的时代，人们越来越认识到，生物多样性的丧失和获得等特征对传播率有很大影响，包括对人类疾病的影响。但宿主生物多样性与传播关联是有争议的，因为很少有系统能够同时操纵暴露剂量和生物多样性。在我们的小鱼/蜗牛/吸虫相互作用模型中，我们将在实验室和中游环境中将暴露试验结合到鱼类和蜗牛的实验群落中，以测试引入非本地蜗牛和鱼类是否可以解释我们在艾伯塔省南部当地水体中观察到的传播率的显著变化。**

All parasites must solve the problem of transmitting infective stages into new hosts. Not surprisingly, ‘transmission rate' is a fundamental parameter in epidemiological models that describe parasite population dynamics, including for problem parasites of humans, domestic animals, and wildlife. The long-term goal of my research program is to understand the factors that determine variation in transmission rates for parasites of wild animals. ******Many parasites have complex life-cycles, the completion of which requires the transmission of infective stages between a sequence of obligate hosts. Some solutions to solving the problem of transmission between hosts are spectacular in their expression. Ants infected with larvae of the fluke, Dicrocoelium, are chauffeured from their nests to adjacent flowers, onto which they remain attached with their mandibles during the evening hours. When temperature warms the next day, they detach and return to their nests. Attachment facilitates transmission of the larvae into grazing mammals. This cycle of attachment/detachment continues for weeks at our study sites in Cypress Hills Park, Alberta where the fluke has been introduced. In this proposal, my students and I combine genomics tools, imaging tools, and behaviour assays to determine if zombie-ism requires physical manipulation of structures in the brain that control mandibular muscles, or the secretion of gene products that lead to neuromodulation, or both. One possibility is that attachment/detachment behaviours are associated with the upregulation of particular gene products that are temperature-dependent. Understanding the mechanisms leading to the cycle of attachment/detachment in infected ants is a key step towards understanding the pervasive phenomenon of host phenotype alteration by parasites, which extends to humans infected with Toxoplasma, and wildlife/pets infected with rabies virus. ******In a second model system, we manipulate infection dose to test hypotheses regarding the factors underlying variation in rates of parasite transmission. My students and I will evaluate how rates of transmission are influenced by the diversity and structure of host communities. In our current age of ever-increasing changes in animal biodiversity, there is an increased recognition that features such as biodiversity loss and gain have strong effects on rates of transmission, including for diseases of humans. But the host biodiversity vs. transmission association is contentious because so few systems are amenable to the manipulation of both exposure dose and biodiversity. In our model minnow/snail/trematode interaction, we will combine exposure trials into experimental communities of fish and snails in lab and mesocosm settings to test whether introductions of non-native snails and fish can explain the marked changes in rates of transmission we have observed in local waterbodies in southern Alberta. **