Submitted to: Proceedings of the ASMS Conference on Mass Spectrometry and Allied Topics
Publication Type: Proceedings
Publication Acceptance Date: 6/5/2005
Publication Date: 6/9/2005
Citation: Bernier, U.R., Allan, S.A., Quinn, B.P., Kline, D.L., Barnard, D.R. 2005. Collection of chicken volatiles in solvents to identify candidate attractants of ornithophilic mosquites implicated in west nile virus transmission. Proceedings of the ASMS Conference on Mass Spectrometry and Allied Topics. Interpretive Summary: None.
Technical Abstract: Mosquitoes that transmit West Nile virus (WNV) and encephalitis feed on both avian and mammalian hosts and this cycle results in the spread of disease to humans. The responsible mosquito species have a much stronger ornithophlic, rather than anthropophilic preference. Laboratory experiments with Culex mosquitoes demonstrate this well when live chicken and human odors are compared in bioassays with an olfactometer. Very few chemical analyses have been conducted to identify the odors emanated by avians; therefore, solvent washings are explored herein as a sample collection approach. Discovery of bloodmeal location cues for host-seeking mosquitoes will allow development of more efficient and effective lures for mosquito trapping, surveillance, and possibly control. Solvent washings from the feet, skin and feathers of chickens were bioassayed to determine their biological activity. Extracts from chicken feathers were further concentrated to identify additional trace level compounds below the detection limit of the method when washings were collected without concentration. Collections were performed with methanol, diethyl ether, and hexane. Samples were analyzed on a ThermoQuest Trace GC/MS, in EI mode, using a 15 m DB-5 x 0.25 mm i.d. column (film thickness 0.25 'm) and 30 m x 0.25 mm i.d. (0.25 'm film thickness) DB-WaxETR and HP-FFAP columns. Candidate attractants were bioassayed in a laboratory olfactometer. Initial Bioassays of Fractions. Washings were collected and bioassayed in a dual port, triple cage olfactometer to assess the ability of the method (and each solvent) to capture volatiles of interest, i.e. attractants. Tests were conducted from 3-10 min with approximately 75 female mosquitoes. In the case of feathers, the hexane washing exhibited the highest level of attraction, followed by the methanol washing, and then the ether washing. Feathers alone were much less attractive than odors from a live chicken. Therefore, it was hypothesized that some attractive odors are not deposited and/or desorbed from the feathers. Washings from chicken feet and skin have been collected and will be bioassayed to compare the attraction of these to that of feathers. Mass Spectrometric Analysis of Fraction. Samples were analyzed and tentative identifications were made of the major components. Compounds were purchased, when available and injected to test against the tentatively identified compounds. Emphasis was placed upon the identification of compounds from feathers because, at this point, feathers are well characterized biologically. Many compounds were identified, including short chain aldehydes (pentanal to decanal), carboxylic acids (butanoic and smaller), and various alcohols. The full list of compounds will be presented. Bioassays of Identified Components. Single compounds (treatments) with and without carbon dioxide were bioassayed against a blank (sample apparatus minus treatment) in the second port of the olfactometer to determine absolute attraction level of each compound or mixture. Aldehydes (benzaldehyde, hexanal, and nonanal) have not elicited attraction in Culex quinquefasciatus. Additional compounds are being screened.