Allelochemicals that modify mosquito host-seeking behavior: Gas chromatography/mass spectrometry and high-field asymmetric-waveform ion mobility spectrometry

Mosquitoes (Diptera: Culicidae) are nuisance pests responsible for the transmission of several human diseases such as yellow fever, malaria, St. Louis encephalitis, Japanese encephalitis and West Nile Virus (WNV). Although the mechanisms that determine host preference are poorly understood, it is known that mosquitoes respond to chemical and physical signals to orient themselves towards a host from a distance, known as mosquito host-seeking behavior. Allelochemicals that modify arthropod host-seeking behavior consist of kairomones and allomones. Kairomones are chemical cues that are used for host finding and are thought to play a large role in this process. Allomones consist of attraction-inhibitors and other repellents that interfere with the host-location process. The primary goal of this research is to contribute to the understanding of the host-seeking behavior in mosquitoes so that new and more effective methods can be employed for controlling mosquito populations.;There have been many attempts to identify possible attractants for several species of mosquitoes. It is known that the mosquito from the Culex specie, the main vector of WNV, feeds primarily on birds, but there is little information in the literature about odors emanating from avian hosts. This problem has been approached in the first objective of this work by the identification of candidate-attractant compounds from chicken skin and feathers, using gas chromatography/mass spectrometry (GC/MS). A thermal desorption method and a sorbent/solvent extraction method were used; when combined with GC/MS, they allowed for the detection of different functional groups of compounds such as carboxylic acids, aldehydes, ketones and alcohols.;The release of allelochemicals in the field is normally accomplished with surveillance traps baited with attractant lures, or appropriate candles or aerosol-dispensing devices to release repellents. The downfield distribution of these compounds in the field and subsequent detection by arthropods is not well understood. The use of high-field asymmetric-waveform ion mobility spectrometry (FAIMS) to characterize the distribution of these plumes in the field is being explored. FAIMS separates ions based on the difference in their mobility at high electric field relative to their mobility at low electric field. The results from initial studies with APCI/FAIMS/MS in the laboratory show promise for FAIMS to be used as a portable instrument that is amenable to the downstream monitoring of the dispersion from targeted compounds from released sources.