Culicoides and Midge-associated Arboviruses on Cattle Farms in Yunnan Province, China

Culicoides spp. (Diptera: Ceratopogonidae) are small biting midges, some of which are the vectors of arboviruses affecting livestock, i.e., African horse sickness virus (AHSV), bluetongue virus (BTV), and epizootic hemorrhagic disease virus (EHDV). Yunnan Province, located in southwestern China, has a history of high prevalence of arboviruses. The diversity and abundance of Culicoides was observed between March 2022 and March 2023 on two cattle farms in Lufeng County of Yunnan Province, China and virus isolation and PCR detection were attempted from cattle blood and Culicoides spp. collected from the farms. Light trap collections contained 19 species of Culicoides belonging to 8 subgenera and one unplaced species group and were dominated by C. oxystoma (63.4%), C. imicola (16.2%), C. arakawae (13.4%), C. sp. near newsteadi (2.3%), and C. orientalis (1.7%). A total of 8,343 Culicoides were used for statistical analysis; from these collections 997 Culicoides specimens belonging to 10 species were screened for the presence of BTV, EHDV, Yunnan Orbivirus (YUOV), and Yongshan totivirus (YSToV) using reverse transcription quantitative PCR (RT-qPCR). One strain of YUOV was isolated from cattle blood and 7 isolates of YSToV were isolated from 5 different species of Culicoides. BTV and YSToV were detected from 2 and 3 pools of parous C. imicola specimens by RT-qPCR, respectively, which is the first report of a totivirus to be associated with Culicoides. Culicoides imicola is likely to be the major vector of Culicoides-borne arboviruses in Lufeng County, which is a relatively dry locality, and adult C. imicola may play a role of BTV overwintering.