| Summary: | The genus <i>Ehrlichia</i> includes tick-borne bacterial pathogens affecting humans, domestic and wild mammals. <i>Ehrlichia minasensis</i> has been identified in different animal species and geographical locations, suggesting that this is a widely distributed and generalist <i>Ehrlichia</i>. In the present study, we evaluated <i>Ehrlichial</i> infection in 148 Equidae presented to the Medical Clinic Department of a Veterinary Hospital from a midwestern region of Brazil. Blood samples and ticks collected from the animals were tested by Polymerase Chain Reaction (PCR) for the presence of <i>Ehrlichia</i> spp. A multigenic approach including Anaplasmataceae-specific (i.e., 16S rRNA, <i>groEL</i>, <i>gltA</i>) and <i>Ehrlichia</i>-specific (i.e., <i>dsb</i> and <i>trp36</i>) genes was used for accurate bacteria identification. Sera samples were also collected and evaluated for the detection of anti-<i>Ehrlichia</i> antibodies by indirect fluorescent antibody test (IFA). Possible associations between molecular and serological diagnostics and clinical and hematological manifestations were tested using chi-squared or Fisher’s exact tests. Sequence analysis of the <i>dsb</i> fragment revealed that three horses (2.03%) were exposed to <i>E. minasensis</i>. Sixty-one (41.2%) Equidae (58 equines and three mules), were seropositive for <i>Ehrlichia</i> spp., with antibody titers ranging between 40 and 2560. Seropositivity to ehrlichial antigens was statistically associated with tick infestation, rural origin, hypoalbuminemia and hyperproteinemia (<i>p</i> ≤ 0.05). The present study reports the first evidence of natural infection by <i>E. minasensis</i> in horses from Brazil.
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