Eastern equine encephalitis virus and identification of host bloodmeal sources from individual Culiseta melanura (Diptera: Culicidae) at an enzootic focus in central New York State.

Toward a more detailed understanding of the Eastern equine encephalitis virus (EEEV) cycle, individual blood-fed Culiseta melanura (Coquillett) mosquitoes were collected at an enzootic focus in New York State. Blooded females were tested for EEEV by multiplex real-time quantitative reverse transcription polymerase chain reaction, qRT-PCR. Host bloodmeals were identified using DNA amplification and sequencing of the cytochrome B gene. In 2018, 577 individual mosquitoes were tested. Virus was detected in the bodies of 16, of which two had the virus in their legs. In 2022, 606 individual mosquitoes were tested, and the virus was detected in the bodies of six, of which one had the virus in its legs. Virus in the legs suggested a disseminated infection. The qRT-PCR cycle threshold (Ct) values for individual bodies ranged from 17.6 to 38.3, and for legs, 22.8 to 28.1. Host sources for 17 of the 22 were: Passeriformes, Bombycillidae, cedar waxwings (Bombycilla cedrorum); Icteridae, red-winged blackbird (Agelaius phoeniceus); Turdidae, American robin (Turdus migratorius), veery (Catharus fuscescens), and wood thrush (Hylocichla mustelina); Vireonidae, yellow-throated vireo (Vireo flavifrons); Passerellidae, song sparrow (Melospiza melodia), and field sparrow (Spizella pusilla); Parulidae, American redstart (Setophaga ruticilla); and Gruiformes, Rallidae, American coot (Fulica americana). In both years, red-winged blackbirds were a source of blood for Cs. melanura in the earliest 2 d after EEEV was detected. Annually, the earliest detection of the virus was in blooded-gravid mosquitoes before non-blooded mosquitoes in 15 of 17 yr. These results support the thesis that birds contribute to the introduction and re-emergence of EEEV to this enzootic focus.