Abstract
The genus Ehrlichia includes tick-borne bacterial pathogens affecting humans, domestic and wild mammals. Ehrlichia minasensis has been identified in different animal species and geographical locations, suggesting that this is a widely distributed and generalist Ehrlichia. In the present study, we evaluated Ehrlichial 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 Ehrlichia spp. A multigenic approach including Anaplasmataceae-specific (i.e., 16S rRNA, groEL, gltA) and Ehrlichia-specific (i.e., dsb and trp36) genes was used for accurate bacteria identification. Sera samples were also collected and evaluated for the detection of anti-Ehrlichia 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 dsb fragment revealed that three horses (2.03%) were exposed to E. minasensis. Sixty-one (41.2%) Equidae (58 equines and three mules), were seropositive for Ehrlichia spp., with antibody titers ranging between 40 and 2560. Seropositivity to ehrlichial antigens was statistically associated with tick infestation, rural origin, hypoalbuminemia and hyperproteinemia (p ≤ 0.05). The present study reports the first evidence of natural infection by E. minasensis in horses from Brazil.
Highlights
Subsequent molecular surveys in Brazil suggest that the Brazilian isolate of Ehrlichia detected in horses may potentially belong to the same group as that detected in Nicaragua [5,22]. Given these antecedents and the lack of studies involving Equine ehrlichiosis in Brazil, this study aims to analyze the occurrence of Ehrlichia spp. and anti-ehrlichial antibodies in horses from the state of Mato Grosso, as well as to evaluate the possible association between bacterial infection and tick parasitism, clinical manifestations, and hematological changes
This paper reports, for the first time, the molecular detection of E. minasensis in horse blood in Brazil
Ehrlichia minasensis was first described in cattle from Canada [36], and later in R. microplus ticks and cattle from Brazil [7,10,36,37]
Summary
Several Ehrlichia bacteria are important pathogens, causing disease in humans and domestic and wild mammals This genus belongs to the order Rickettsiales, family Anaplasmataceae, and has six recognized species: Ehrlichia canis, Ehrlichia chaffeensis, Ehrlichia ewingii, Ehrlichia muris, Ehrlichia ruminantium and Ehrlichia minasensis [1,2]. Equine ehrlichiosis has mostly been associated with agents of the genera Neorickettsia (i.e., N. risticii) and Anaplasma (i.e., A. phagocytophilum) [1]. In addition to these species, commonly reported to cause Equine ehrlichiosis, infection by bacteria of the genus Ehrlichia has been described in horses in the United States [3,4], and Nicaragua [5]. Ehrlichia minasensis species has been detected in cattle [10], cervids [11] and several tick species within the genera Rhipicephalus [2,7,12,13], Amblyomma [13], Hyalomma [14,15], and Haemaphysalis [16]
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