Mosquitoes in the fall: Effects of age and photoperiod on the transcriptome of Culex pipiens

The northern house mosquito, Culex pipiens, is abundant in the temperate zones of the United States. This species is of particular interest from an epidemiological perspective as it is considered the primary vector of West Nile Virus (WNV) to humans and has been implicated in the transmission of other arboviral diseases such as St. Louis encephalitis and Rift Valley fever. During the active season (June - August), Cx. pipiens is ornithophilic with the American robin (Turdus migratorious) being a primary blood host. Importantly, previous studies have shown that during the later portion of the active season, from late August into October, the proportion of Cx. pipiens feeding on mammals increases significantly, coinciding with annual peaks in WNV transmission to humans. This shift has been linked to declines in the availability of bird hosts due to fall migrations. However, under low photoperiod conditions, newly eclosed adults enter pre-diapause and cease blood feeding, causing the average population age of host-seeking Cx. pipiens to increase as the fall progresses and daylight decreases. We developed experiments to isolate the effects of age and short photoperiod on the transcriptome of non-diapausing adult Cx. pipiens. Results of these analyses may inform future epidemiological models and contribute to more effective management of Culex vector