Vectors in the (out)field: Do sylvatic Culicoides species present a bluetongue virus risk to pastured cattle?

The majority of work done on the role of Culicoides species as bluetongue virus vectors has focused on feedlot dairy and captive cervid production. These systems represent two extremes of potential Culicoides habitats: open and arid with no vegetation, and wooded with abundant flora and refugia. In the southeast US, cow/calf producers raise animals on pastures, which often have woodlands integrated into them, or are adjacent to woodlands. Little data exists on the Culicoides species present in these habitats that fall in the middle of the agricultural-sylvatic habitat spectrum. To determine whether putative bluetongue virus vector species were present in cattle pastures, we collected Culicoides from pastures and adjacent woods at two locations in northwest Arkansas during August-October 2021 and 2022. 964 Culicoides representing 15 species were collected during the course of the study. Woods collections had both higher abundance and species richness, but C. haematopotus and C. stellifer were the most abundant species collected in both the woods and pasture. C. stellifer, a putative BTV vector, was collected in significantly higher abundance in CO2 traps in the pasture than in the woods, suggesting that midges in the pasture were actively host seeking, while those in the woods were not. This species may be actively leaving the forest to feed on cattle, putting animals at risk of transmission. Future research will examine the directionality of Culicoides movement across the landscape to determine how midges utilize different habitat types for oviposition/resting and feeding.