Evidence of Crimean-Congo hemorrhagic fever virus in livestock and wildlife in Northeastern Portugal.

Following the death of an 83-year-old man from the district of Bragança, in north-eastern Portugal due to Crimean-Congo hemorrhagic fever (CCHF), a serological survey was conducted to investigate domestic and wild ruminants. The survey included samples from cattle(n = 94), sheep(n = 30), goats(n = 4), and red deer(n = 10) collected within the affected region and neighboring areas where the human case was reported. CCHF antibodies were detected by ELISA in the serum of sheep, cattle and red deer, corresponding to seropositivity rates of 3.33%, 38.29%, and 60%, respectively, indicating significant exposure to the virus. Indirect immunofluorescence assays further validated the ELISA results. Most of the positive cattle originate from farms located in the Guarda district, which are located close to the Spanish border. None of the goats was positive for CCHFV-antibodies and viral-RNA was not detected in any of the samples. CCHFV-RNA was also not detected in 15 ticks from Dermacentor and Rhipicephalus genera collected from vegetation or cattle, on one of the positive farms. Our findings suggest that CCHFV is actively circulating in northeastern Portugal. Reports of human cases of CCHF in Spain, particularly near the border with Portugal, are consistent with the detection of CCHFV-RNA in ticks feeding on domestic and wild animals in western Spain, highlighting the potential for cross-border transmission and suggesting an established circulation of CCHFV in the Iberian Peninsula.