Borrelia miyamotoi exceeds Borrelia burgdorferi sensu lato in human exposure despite the opposite in ticks: an integrated serological, entomological and molecular study in southeastern Kazakhstan.

Lyme borreliosis (LB) and hard tick-borne relapsing fever caused by Borrelia miyamotoi are emerging tick-borne infections, yet in Kazakhstan routine LB diagnosis relies on single-tier enzyme immunoassay (EIA) without confirmatory testing, and B. miyamotoi is absent from national diagnostic protocols. In 2024-2026, 1300 participants were enrolled in the Ixodes persulcatus-endemic Almaty and Jetisu regions and the non-endemic Zhambyl and Turkistan regions, across diverse clinical and tick-exposure groups. All sera were screened for IgM and IgG to both pathogens by multi-antigen protein arrays, with subsets tested by the LymeBest ELISA and the Anti-Borrelia EUROLINE-WB immunoblot. In addition, 503 ticks removed from participants were tested for borrelial DNA by PCR. Seroreactivity to B. burgdorferi sensu lato (s.l.) was rare (4/1300, 0.3%), whereas B. miyamotoi seroreactivity was more frequent (31/1300, 2.4%) and concentrated in tick-exposed groups. In ticks the pattern was the opposite: B. burgdorferi s.l. DNA was detected in 37/503 ticks (7.4%; 45.3% in I. persulcatus) and B. miyamotoi DNA in 7/64 I. persulcatus (10.9%), with four ticks co-infected, the single B. miyamotoi strain typed by eight-locus MLST matched a sequence type reported from Japan, Mongolia and China. Of the 28 participants bitten by Borrelia DNA-positive ticks who provided follow-up sera, three (10.7%) seroconverted, one to B. burgdorferi s.l. and two to B. miyamotoi. One of the latter, PCR-positive for B. miyamotoi DNA in baseline blood, is, to our knowledge, the first molecularly confirmed case of B. miyamotoi infection in Kazakhstan. The LymeBest ELISA agreed poorly with the other two assays: none of its 27 positive baseline results was confirmed by immunoblot or protein array. In contrast, immunoblot confirmed two of the four baseline samples seroreactive to B. burgdorferi s.l. by protein array, as well as the B. burgdorferi s.l. seroconversion. These findings support two-tier serological testing for LB and dedicated B. miyamotoi diagnostics in Kazakhstan.