Infection of hard ticks in the Caspian Sea littoral of Iran with Lyme borreliosis and relapsing fever borreliae

•The Ixodes ricinus is a highly prevalent tick species in the Caspian Sea littoral of Iran.•Ixodes ricinus ticks had infections with Lyme borreliosis spirochetes or the relapsing fever Borrelia, B. miyamotoi.•A Borrelia identified in Rhipicephalus ticks shared the highest identity with an isolate infecting Haemaphysalis megaspinosa ticks in Japan.•The BLAST and phylogenetic analysis suggest the range expansion of the European I. ricinus-associated borreliae into the north of Iran. The Caspian Sea littoral of Iran is home to various hard tick species, including Ixodes ricinus, the notorious vector of Lyme borreliosis (LB) in Eurasia. Here, in this area, we examined I. ricinus and other hard ticks, along with common rodents and small mammals for LB and relapsing fever (RF) borreliae infection. Ticks were collected from various mammalian hosts, including sheep, goats, cattle, camels, horses, dogs, donkeys, rodents, and hedgehogs. Rodents and small mammals were live-captured from different habitats. A real-time PCR for 16S rRNA sequence revealed borrelial DNA in 71 out of 501 (≈14 %) specimens belonging to I. ricinus and Rhipicephalus ticks. None of the rodents and small mammals showed borrelial infection in the viscera. PCR amplification and sequencing of a 600-bp sequence of the flaB identified Borrelia bavariensis, Borrelia garinii, Borrelia afzelii, and Borrelia valaisiana, and the RF Borrelia, B. miyamotoi in I. ricinus ticks. The RF-like Borrelia in Rhipicephalus ticks shared the highest identity (98.97 %) with an isolate infecting Haemaphysalis megaspinosa ticks in Japan. Our phylogeny and BLAST analysis suggest the range extension of the European I. ricinus-associated borreliae into the north of Iran.