Detection and genetic characterization of Crimean-Congo hemorrhagic fever virus in ticks from western Spain (2017, 2020-2024).

Abstract

Introduction: Crimean-Congo hemorrhagic fever virus (CCHFV) was first detected in Spain in ticks collected from red deer in southwestern Cáceres. Since then, this region, established as endemic, has been the focus of several surveillance studies. However, updated data on viral circulation in this area remain limited. Materials and methods: We conducted a retrospective surveillance study to assess the presence and genetic diversity of CCHFV in ticks collected in central and southern Cáceres over multiple years (2017 and 2020-2024). A total of 3,183 ticks, grouped into 1,569 pools, were collected from wild ungulates, livestock, domestic animals and vegetation, and analyzed by two PCR methods. Positive pools were characterized by Sanger sequencing. Results: CCHFV was exclusively detected in Hyalomma lusitanicum ticks, with an overall infection rate of 1.54% (95% CI: 1.14-2.03). Most positive pools originated from wild ungulates, particularly red deer. Genetic analysis revealed the circulation of two CCHFV genotypes, predominantly genotype III. Discussion: The detection of CCHFV in ticks collected over multiple years supports the sustained circulation of the virus in southwestern Cáceres. Our findings also reinforce the key role of H. lusitanicum as the main vector maintaining the virus in wild ungulates and underscore the genetic diversity of circulating strains and the importance of using multiple molecular methods. These results emphasize the need for continuous surveillance in endemic areas to monitor viral circulation and assess animal and public health risks.