A new Borrelia on the block: Borrelia miyamotoi – a human health risk?

Abstract

Background Borrelia miyamotoi clusters phylogenetically among relapsing fever borreliae, but is transmitted by hard ticks. Recent recognition as a human pathogen has intensified research into its ecology and pathogenic potential. Aims We aimed to provide a timely critical integrative evaluation of our knowledge on B. miyamotoi , to assess its public health relevance and guide future research. Methods This narrative review used peer-reviewed literature in English from January 1994 to December 2018. Results Borrelia miyamotoi occurs in the world’s northern hemisphere where it co-circulates with B. burgdorferi sensu lato, which causes Lyme disease. The two borreliae have overlapping vertebrate and tick hosts. While ticks serve as vectors for both species, they are also reservoirs for B. miyamotoi . Three B. miyamotoi genotypes are described, but further diversity is being recognised. The lack of sufficient cultivable isolates and vertebrate models compromise investigation of human infection and its consequences. Our understanding mainly originates from limited case series. In these, human infections mostly present as influenza-like illness, with relapsing fever in sporadic cases and neurological disease reported in immunocompromised patients. Unspecific clinical presentation, also occasionally resulting from Lyme- or other co-infections, complicates diagnosis, likely contributing to under-reporting. Diagnostics mainly employ PCR and serology. Borrelia miyamotoi infections are treated with antimicrobials according to regimes used for Lyme disease. Conclusions With co-infection of tick-borne pathogens being commonplace, diagnostic improvements remain important. Developing in vivo models might allow more insight into human pathogenesis. Continued ecological and human case studies are key to better epidemiological understanding, guiding intervention strategies.

Whole genome sequencing of Borrelia miyamotoi isolate Izh-4: reference for a complex bacterial genome

“…Genetically B. miyamotoi has been divided into distinct populations, with population boundaries apparently determined by vector association [2,8,16,32,33]. To investigate genetic differences in B. miyamotoi populations, comparative genomics should be employed, but this requires high quality reference genomes [56].…”

“…Subsequently it was discovered to be occurring sympatrically with B. burgdorferi sensu lato in several Ixodes species that also transmit Lyme disease spirochetes. These included Ixodes persulcatus in Eurasia [2][3][4][5][6][7], I. scapularis [8][9][10][11] and I. pacificus [12][13][14][15] in North America, and I. ricinus in Europe [16][17][18][19][20]. The prevalence of B. miyamotoi in ticks was found to be usually lower than that of B. burgdorferi s.l.…”

“…Despite its co-occurrence with B. burgdorferi s.l. in hard-bodied Ixodes ticks, genetic and phylogenetic analyses showed that B. miyamotoi belongs to the clade of relapsing fever (RF) spirochetes [1,2,16,23,27], which are usually transmitted by soft ticks (Argasidae) or lice. Similar to other relapsing fever species, B. miyamotoi possesses genes encoding variable large proteins and variable small proteins (Vlp and Vsp, respectively) [11,28,29].…”

“…Genetic studies on field-collected samples suggested that there is little genetic variability of B. miyamotoi isolates within the population of a single tick species, whilst B. miyamotoi isolates from different tick species appeared genetically heterogeneous [3,22]. Thus, it was suggested that the species B. miyamotoi consists of Asian, European, North American -West and East Coast -ecotypes/genotypes [2,8,16,32,33].…”

“…Since then, several hundred BMD cases were identified in Russia [34,35]. BMD cases have been reported in Europe and the USA as well, but not with such frequency [2,[36][37][38][39]. Cases that were reported from Western Europe often involved immunocompromised individuals, but more recently also immunocompetent persons [40,41].…”