Crimean-Congo hemorrhagic fever virus lineages Europe 1 and Europe 2 in Bulgarian ticks

Crimean-Congo hemorrhagic fever (CCHF) is a tick-borne human viral disease with fatality rate up to 30%. Two genetic lineages of CCHF virus (CCHFV) are present in Europe - lineage Europe 1 which contains pathogenic CCHFV strains, and lineage Europe 2 consisting of AP92 and AP92-like strains. In order to investigate CCHFV distribution and potential risk for humans, ticks were collected from livestock in the five districts where CCHF cases have been reported in the last five years in Bulgaria. CCHFV lineage Europe 1 was detected in 39 of 623 Hyalomma marginatum ticks (6.3%; range per village 2.7-15.2%), while CCHFV lineage Europe 2 was detected for the first time in Bulgaria in 49 of 415 Rhipicephalus sanguineus sensu lato ticks (11.8%; range 0-58.3%). The present study shows that both Europe 1 and Europe 2 CCHFV lineages are present in Bulgaria. The pathogenic role of the AP92-like strains remains to be elucidated.