Five-year spatio-temporal occurrence of Culicoides biting midges and arbovirus surveillance at livestock-associated sites in the Republic of Korea, 2021–2025

Culicoides biting midges are hematophagous vectors of arboviruses in livestock, and characterizing their occurrence patterns is fundamental to disease surveillance. Field collections show substantial year-to-year variation, complicating characterization of dominant-species occurrence from a single season or site. This study integrated five years of Culicoides collection data from livestock-associated sites in the Republic of Korea to describe species composition, year-to-year variation, site-level dominance, and seasonal occurrence patterns of dominant species, while screening collected Culicoides for selected arboviruses of veterinary importance. Culicoides spp. were collected biweekly from May to October during 2021–2025 at nine livestock-associated sites (seven cattle sheds and two racetracks) using ultraviolet blacklight traps. Specimens were identified morphologically, with molecular confirmation by COI sequencing when required. All pooled samples were screened by RT-PCR for bluetongue virus (BTV), African horse sickness virus (AHSV), and Simbu serogroup viruses. Descriptive summaries of species composition, year-to-year variation, site-level dominance, and seasonal occurrence were complemented by PERMANOVA and NMDS based on Bray–Curtis dissimilarities as supplementary analyses. A total of 41,259 individuals were collected from 476 collection events, of which 277 were positive, and 199 yielded no Culicoides . The community was strongly dominated by three species ( C. arakawae , C. punctatus , and C. oxystoma ), which together accounted for 95.1% of all individuals. Mean abundance per collection event was the highest in 2021 and 2022 and substantially lower during 2023–2025, while dominant species composition varied among years. Most sites were dominated by either C. arakawae or C. punctatus , and mean seasonal abundance peaked in June for C. punctatus , August for C. arakawae , and September for C. oxystoma . Site effects on community composition exceeded year effects, and none of the 766 Culicoides pools screened tested positive for BTV, AHSV, or Simbu serogroup viral RNA. Although this dataset does not constitute a spatially balanced nationwide survey, integrating multi-year livestock-associated collection data provides a descriptive baseline for the spatio-temporal occurrence of dominant Culicoides species and arbovirus screening in the Republic of Korea, supporting future vector surveillance and risk assessment.