Identification of avian- and mammalian-derived bloodmeals in Aedes vexans and Culiseta melanura (Diptera: Culicidae) and its implication for West Nile virus transmission in Connecticut, USA

To evaluate the host-feeding patterns of Aedes vexans (Meigen) and Culiseta melanura (Coquillett) as secondary vectors of West Nile virus (family Flaviviridae, genus Flavivirus, WNV) in Northeastern United States, we identified the source of vertebrate bloodmeals by sequencing portions of the cytochrome b gene of mitochondrial DNA. Analysis of polymerase chain reaction products from a total of 119 Ae. vexans revealed that 92.4% of individuals acquired blood solely from mammalian and 2.5% from avian hosts. Mixed bloodmeals from both avian and mammalian hosts were detected in 5% of individuals of this species. Ae. vexans obtained vertebrate bloodmeals most frequently from white-tailed deer (80%) followed by domestic horse, American robin, eastern cottontail, and domestic cat. In contrast, Cs. melanura fed predominantly on avian species (89.6%) but exhibited some inclination for mammalian blood (4.2%). Individual mosquitoes containing mixed bloodmeals were also identified in 6% of Cs. melanura. American robin was the most common source of vertebrate blood for Cs. melanura (23%), followed by wood thrush and gray catbird. American crow represented only 2% of the bloodmeals identified in Cs. melanura, as was similarly found with other recognized Culex vectors of WNV in the northeast. These findings support the view that Ae. vexans is likely to be a relatively important "bridge vector" to large mammals, including deer and horse, whereas Cs. melanura likely plays a secondary role in enzootic transmission of WNV among free-ranging birds in more rural environs.