Abstract
Culex pipiens serves as the endemic vector of West Nile virus (WNV) in eastern North America, where house sparrows (HOSP, Passer domesticus) serve as a reservoir host. We tested the hypotheses that: (1) Attraction of Cx. pipiens to HOSP is influenced by bird age and (2) that age-specific variation in chemical profiles of bird uropygial gland secretions informs this choice. We conducted mosquito choice trials in an olfactometer and found that Cx. pipiens were more often attracted to adult sparrows over nestlings, however, they demonstrated no preference for adults over fledglings. Using gas chromatography-mass spectrometry we observed age-specific differences in the semi-volatile chemical profiles of house sparrow uropygial gland secretions. Contrary to our hypothesis, we found no significant difference in mosquito feeding preference between the secretions of adults and those of either nestlings or fledglings. We suggest that other chemical cues influence the feeding preference of Cx. pipiens, either independently of uropygial gland secretions, or synergistically with them.
Highlights
In the eastern United States, West Nile virus (WNV) is maintained in bird reservoir host populations by Cx. pipiens [1], which survives high viral titers [2], is abundant [3], and feeds readily on birds [2]
GC-MS analysis indicated that HOSP uropygial secretions contain complex mixtures of semivolatile esters
Consistent with Scott et al.’s study of HOSP and Cx. quinquefasciatus, we found that Cx. pipiens are more often attracted to live adult HOSP over nestlings
Summary
In the eastern United States, West Nile virus (WNV) is maintained in bird reservoir host populations by Cx. pipiens [1], which survives high viral titers [2], is abundant [3], and feeds readily on birds [2]. The factors that influence the interaction between the reservoir hosts and the mosquito vectors are key to the maintenance of the cycle. Other studies report that Culex mosquitoes show no age-based preference [8] and concluded that nestling birds were not important amplification hosts in the WNV cycle in their region [9]. The role of host age in the WNV cycle remains under debate. Mosquitoes locate blood meals in part through carbon dioxide, but as a by-product of respiration, it alone cannot explain why mosquitoes demonstrate species-specific host preferences [10,11,12]. Host choice is likely influenced by more species-specific chemical profiles [11,13]. One source of chemical cues that mosquitoes may use is the uropygial gland. Located at the base of the tail, the gland is the source of a diverse mixture of organic
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