Identifying novel tick attractants and repellents by exploiting their olfactory and eco-physiology

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PROJECT SUMMARY Black-legged tick, Ixodes scapularis, have doubled their distribution range within the past 2 decades. Not surprisingly, Lyme disease incidence has tripled since the 1990s according to the recent NIH tickborne diseases strategic planning committee’s report. These vector/disease expansions have been attributed to climate change, neighborhoods encroaching the animal habitats, and other ecologic shifts. Multi-pronged strategies, especially those that are based on understanding the ticks’ unique olfactory system and eco-physiological adaptations will provide effective practices that can be embedded into the existing vector control strategies. Ticks display robust olfactory driven behaviors despite endowed with a simple olfactory machinery made of ca. 20 olfactory sensilla (housing ca. 80-90 olfactory receptor neurons, ORNs). How can such relatively simple olfactory system accomplish the remarkable task of detecting and discriminating between the preferred hosts and mates, or, to avoid the unfavorable ones? We will answer this question by determining the detection properties of each of the sensilla challenging with odors of demonstrated behavioral response. We propose to use the single sensillum recording (SSR) method to record the odor induced activity from individual ORNs, The SSR will be further coupled with gas-chromatography (GC-SSR) to directly isolate biologically active constituents odorant from the complex odors mixtures. These constituents will be chemically identified using mass spectrometry, and finally verified by injecting them back into GC-SSR. Electrophysiologically active chemicals will be tested for the behavioral response in a 4-arm olfactometer- either individually or in blends. In arthropods, a distinct yet limited range of volatiles from the environment are parsimoniously used in various contexts, eliciting distinct behaviors such as attraction to host and mates, and repulsion/avoidance from unsuitable sites. Odors, such as pheromones, are effective means to sample and control vector arthropods including ticks, yet identifying an effective and selective bait has been elusive so far. Therefore we believe that our proposed integrated platform will lead to the discovery of novel natural attractants and repellents. This project will extend the fundamental understanding of the ticks’ olfactory biology, and integrating this knowledge with the eco-physiological determinants such as saturation deficit will lead to design of novel management strategies.