Chemical ecology of ticks: olfaction, behaviour, chemistry and control

蜱虫是所有吸血节肢动物中最广泛的致病生物体，在传播对人类和兽医健康具有重要意义的病原体方面仅次于蚊子。 蜱虫几乎完全失明，依靠化学感觉来识别和定位宿主以获得成功的血液餐，与昆虫相比，蜱虫化学感觉系统代表了一个新的前沿。触角的缺乏，嗅觉感受器的存在很少，用于挥发性检测的独特器官（Haller's）的发展，位于口部的感受器的多模式作用，使蜱虫成为了解螨类如何检测化学物质的理想系统。主要的化学感受器官是位于第一对腿的前跗骨上的哈勒器官。除了检测宿主利它素外，Haller的器官化学感受器被认为参与检测信息素、聚集化学物质和环境线索。尽管Haller器官在蜱外周感觉系统中起着关键作用，但对其在化学感觉中的功能知之甚少。以前的研究证实了它在嗅觉中的作用，但不是味觉，直到最近才有报道说它也参与了挥发物的检测。这是重要的，因为大多数蜱虫的驱避性测定不区分由于嗅觉引起的驱避性与来自触觉化学感受/味觉的驱避性。嗅觉感受器能够检测挥发性分子，并且有证据表明嗅觉至少部分地参与蜱对驱避剂的反应。我的研究计划的长期目标是解决我们对蜱虫宿主选择/接受的理解中的关键差距，揭示化学线索感知背后的机制，提供预防蜱虫叮咬以及人类和动物感染的方法。我们将通过研究蜱虫嗅觉的神经感觉生理学和化学生态学来实现这一目标，作为阐明宿主接受/拒绝化学的基础。我的研究计划将揭示人/动物蜱虫相互作用背后的动力学，将气味和化学线索引起的神经生理反应与蜱虫中相应的诱导和观察到的行为联系起来。刺激物将包括宿主的挥发物和天然驱避产品，包括精油和其他行为活性化合物，以确定宿主附着和蜱虫驱避性的相关性。我的研究计划将提供有关蜱的嗅觉敏感性的关键信息，它们敏感的气味库，以及特定天然化合物的驱避活性的行为调查。了解蜱虫化学感受的基本生物学对加拿大和全球都很重要，因为它形成了必要的平台，最终设计出避免传播莱姆病等疾病的病原体传播的机制。

Ticks vector the widest array of disease-causing organisms of all hematophagous arthropods and are second only to mosquitoes in their capacity to transmit disease agents of importance to human and veterinary health. Being almost totally blind, ticks rely on chemosensation to identify and locate hosts for a successful blood meal, and the tick chemosensory system represents a new frontier compared with that of insects. The lack of antennae, the presence of very few olfactory sensilla, the development of a distinctive organ (Haller's) used for volatile detection, the multimodal role of sensilla located on mouth parts, make ticks an ideal system for understanding how acarines detect chemicals. The main chemosensory organ is represented by the Haller's organ, located on the foretarsus of the first pair of legs. Other than detecting host kairomones, Haller's organ chemoreceptors are suggested to be involved in the detection of pheromones, aggregation chemicals, and environmental cues. Despite the pivotal role of the Haller's organ in the tick peripheral sensory system, little is known about its function in chemosensation. Previous studies confirmed its role in olfaction but not gustation, and only recently pedipalps have been reported to be involved in volatile detection as well. This is significant because most repellency assays for ticks do not discriminate between repellency due to olfaction versus that from tactile chemoreception/gustation. Olfactory sensilla are able to detect volatile molecules, and evidence suggests that olfaction is involved at least, in part, in tick responses to repellents. The long-term objective of my research program is to address critical gaps in our understanding of tick host selection/acceptance, unveiling the mechanisms behind chemical cue perception, providing means to prevent tick bites and thus infections in humans and animals. We will achieve this by studying the neuro-sensory physiology and chemical ecology of tick olfaction as a basis for elucidating the chemistry of host acceptance/rejection. My research program will unveil the dynamics behind human/animal-tick interactions by linking the neurophysiological response elicited by odorants and chemical cues with the corresponding induced and observed behaviour in ticks. Stimuli will include volatiles of hosts and natural repellent products including essential oils, and other behaviourally-active compounds, to determine relevance in host attachment and tick repellency. My research program will provide critical information regarding olfactory sensitivity in ticks, the odorant repertoire to which they are sensitive, and behavioural investigations of the repellent activity of specific natural compounds. Understanding the fundamental biology of tick chemosensation is important to Canada and globally as it forms the necessary platform to ultimately devise mechanisms to avoid the transmission of pathogens that vector diseases, like Lyme disease.