Effects of vesicular stomatitis virus infection on circadian rhythm activities of Culicoides sonorensis

Culicoides biting midges (Diptera: Ceratopogonidae) are nuisance pests and important biological vectors of many arboviruses, including orbiviruses and vesicular stomatitis virus (VSV). Adult female midges are hematophagous pool feeders and acquire viruses after feeding on infected hosts. Previous studies have shown that these viruses disseminate to sensory tissues of Culicoides, including the Johnston’s organ, ganglia, and ommatidia. We hypothesize infection of these tissues alters midge sensory function leading to changes in their circadian rhythmic behaviors. Because most species of Culicoides are crepuscular, current surveillance methods rely on light-baited suction traps placed overnight near livestock animals or larval development sites. Changes in midge circadian rhythms following infection with an arbovirus could impact our ability to effectively survey infected midge populations and may change midge host-seeking behaviors. In this study, colonized Culicoides sonorensis adults were fed defibrinated sheep blood mixed with VSV or virus-free media, and daily activities of fully engorged females were monitored using Drosophila activity monitors (DAMs) for seven days. Changes in circadian activities as a result of VSV infection were noted. The results from our experiments provide not only a foundational understanding of C. sonorensis circadian activity but also give insight into the effect virus infection imparts on these activities. These results will help enhance our efficacy in trapping and surveying infected midges, which can also inform risk assessment for VSV transmission.