Studies on the Volatiles Composition of Stored Sheep Wool, and Attractancy toward Aedes aegypti Mosquitoes

SIMPLE SUMMARY: In order to discover new natural remedies for controlling insect vectors, stored sheep wool was tested for its attractiveness to mosquitoes. The volatile compounds from the wool were collected. A total of 52 compounds were detected; many of them known to have mosquito attractant activity against various species. The most abundant compound in the sheep wool hydrodistillate was not attractive for female adult Aedes aegypti mosquitoes in small-scale lab evaluations. Comparative evaluations of raw sheep wool in two semi-field, large, screened outdoor cages each with bait equipped with a U.S. Centers for Disease Control (CDC) trap, revealed the bait with vibrated sheep wool was the best attractant for female adult Ae. aegypti mosquitoes compared to the setups without wool or not vibrated. It was concluded that sheep wool, an easily available, affordable, and environment-friendly material, could be considered as a potential tool to be used in dynamic bait setups for mosquito management and surveillance. ABSTRACT: To discover new natural materials for insect management, commercially available stored sheep wool was investigated for attractancy to female adult Aedes aegypti mosquitoes. The volatiles from sheep wool were collected by various techniques of headspace (HS) extractions and hydrodistillation. These extracts were analyzed using gas chromatography–mass spectrometry (GC-MS) and gas chromatography–flame ionization detector (GC-FID) coupled with GC-MS. Fifty-two volatile compounds were detected, many of them known for their mosquito attractant activity. Seven compounds were not previously reported in sheep products. The volatile composition of the extracts varied significantly across collections, depending on the extraction techniques or types of fibers applied. Two types of bioassay were conducted to study attractancy of the sheep wool volatiles to mosquitoes: laboratory bioassays using glass tubes, and semi-field bioassays using large, screened outdoor cages. In bioassays with glass tubes, the sheep wool hydrodistillate and its main component, thialdine, did not show any significant attractant activity against female adult Ae. aegypti mosquitoes. Semi-field bioassays in two large screened outdoor cages, each equipped with a U.S. Centers for Disease Control (CDC) trap and the various bait setups with Vortex apparatus, revealed that vibrating wool improved mosquito catches compared to the setups without wool or with wool but not vibrating. Sheep wool, when vibrated, may release intensively volatile compounds, which could serve as olfactory cues, and play significant role in making the bait attractive to mosquitoes. Sheep wool is a readily available, affordable, and environment-friendly material. It should have the potential to be used as a mosquito management and surveillance component in dynamic bait setups.