Equine sentinels and one health: a comprehensive serological survey of Crimean-Congo hemorrhagic fever virus in southeastern and Central Europe

Crimean-Congo hemorrhagic fever (CCHF) is the widespread tick-borne viral disease affecting humans with endemic circulation across Africa, Asia, Eastern and Southern Europe. Climate change, global travel, and animal trade have accelerated the expansion of Hyalomma spp., the primary tick vectors of CCHF, into previously non-endemic areas, including the Czech Republic. To assess the current distribution of CCHF in equids across Southeastern and Central Europe, we screened serum samples from horses and donkeys from Bulgaria ( n = 579), Romania ( n = 1,534), and the Czech Republic ( n = 576) by the ELISA kit to detect anti-CCHF antibodies. We observed a clear southeast-to-northwest gradient in seroprevalence: 14.5% (Bulgaria), 1.5% (Romania), and 0% (Czech Republic). These findings correlate with regional environmental conditions and vector distribution and indicate the northward spread of Hyalomma spp. This suggests that climate- and land-use driven ecological changes create conditions for CCHF circulation in regions previously considered low risk.