Culicoides (Diptera: Ceratopogonidae) in Extra-Amazonian Oropouche Outbreak Areas of Minas Gerais, Brazil: Ecological Insights into Virus Transmission

Oropouche fever (OF), caused by Oropouche virus (OROV), has expanded beyond its Amazonian range into Minas Gerais (MG), Brazil, raising concern about transmission in extra‑Amazonian Atlantic Forest landscapes. Critical gaps persist regarding Culicoides vector communities, anthropophily, and climate-sensitive transmission risk in these newly affected regions. We conducted targeted entomological surveys in five MG outbreak communities using CDC light traps and Protected Human Attraction (PHA) to characterize Culicoides composition. Females underwent RT-qPCR for OROV (n = 819) and physiological assessment (n=312). We developed an entomological alert framework that integrates blood-fed abundance, minimum infection rate (MIR) upper confidence bounds, and environmental drivers via generalized additive mixed models, which explained 68% of the variability in Culicoides abundance and the alert index across communities. We collected 1,171 Culicoides representing five species, C. leopoldoi (79.1%) and the primary vector C. paraensis (20.3%) predominated. C. paraensis was documented for the first time in all five outbreak areas and dominated PHA captures (90%), confirming anthropophily. Although no specimens tested OROV-positive (consistent with expected field infection rates of 0.01–1%), MIR upper bounds reached 132/1,000 in low-sample settings and humidity and temperature strongly modulated abundance. This operational baseline and alert index transform virologically negative, sparse surveillance data into prioritized targets for in-tensified sampling and vector control during early, low‑prevalence phases, when con-tainment of OROV’s extra‑Amazonian spread is still achievable.