Borrelial Diseases Across Eurasia

This comprehensive review explores the distribution, diversity, and epidemiology of tick-borne borrelioses across Eurasia, focusing on Lyme borreliosis (LB) and other Borrelia-related infections. The genus Borrelia is categorized into three major groups, the Lyme Group (LG), the Relapsing Fever Group (RFG), and the Echidna–Reptile Group (REPG), each with distinct vectors, reservoirs, and pathogenic profiles. LB, caused by Borrelia burgdorferi sensu lato, is highly endemic in Europe and is increasingly reported in Asia, although it is underdiagnosed in Southeast Asia due to limited surveillance. This review details the ecological dynamics of tick vectors—primarily Ixodes spp.—and their vertebrate hosts, emphasizing the role of migratory birds and climate change in disease spread. It also highlights the presence of relapsing fever Borrelia species transmitted by soft ticks (Ornithodoros spp.) and the emergence of novel species such as Borrelia miyamotoi (RFG) and Borrelia turcica (REPG). This study underscores the need for harmonized surveillance systems, improved diagnostic tools, and integrated public health strategies to address the growing threat of borreliosis in Eurasia.