Abstract
Ehrlichia minasensis, a recently described Ehrlichia species that is the most closely related to, but clearly distinct from, Ehrlichia canis, has been circulating in not only bovines, cervids, and dogs but also several tick species from Canada, Brazil, France, Pakistan, Ethiopia, and Israel. However, there are no reports of E. minasensis in China. The purpose of this study was to explore whether E. minasensis is present naturally in ticks in China. Through PCR targeting of the genus-conserved dsb gene, E. minasensis DNA was detected in Haemaphysalis hystricis ticks removed from free-ranging sheep in Hainan Province, South China in 2017. The partial sequence of the dsb, 16S rRNA, and groEL genes demonstrated that the Hainan strain shared 99% identity with the dsb gene of E. minasensis strain UFMG-EV (GenBank: JX629808), with the 16S rRNA of E. minasensis isolate E-2650 (MH500005) and with the groEL gene of E. minasensis strain UFMG-EV (JX629806), respectively. Moreover, sequence analysis of the major immunogenic tandem repeat protein (trp36) revealed that the Hainan strain harbored a unique tandem repeat sequence (APEAAPVSAPEAAPVSAPVS) and a C-terminal region that differed from those of other known E. minasensis strains. Additionally, phylogenetic analysis based on the entire amino acid sequence of trp36 revealed that the Hainan strain was closely related to a recently described E. minasensis strain from Brazil, of which the sister clade contained different strains of E. canis. The discovery of this novel Hainan strain in H. hystricis ticks represents the first known natural presence of E. minasensis in South China, highlighting the need for its constant surveillance.
Highlights
Ehrlichiosis, which is caused by an obligate, intracellular, gram-negative, tick-borne alphaproteobacterium within the genus Ehrlichia, is an emerging disease in humans, domestic animals, and mice worldwide [1]
Whereas other Ehrlichia species and Ehrlichia-like organisms have been detected in Haemaphysalis hystricis (H. hystricis), E. minasensis has not been detected in this tick species so far [14,15]
Upon comparison with sequences available from the GenBank database, the dsb, 16S rRNA, and groEL genes of the E. minasensis Hainan strain identified in this study (GenBank MN463729) were found to have 99% partial coding sequence (CDS) similarity to the dsb genes from E. minasensis strain UFMG-EV (JX629808; 363/365), isolate E-2650 (MH500007; 343/344), strain 1E (KM015219; 325/329) and to the 16S rRNA of E. minasensis isolate E-2650 (MH500005; 342/345) as well as to the groEL gene of E. minasensis strain UFMG-EV (JX629806; 624/626), respectively
Summary
Ehrlichiosis, which is caused by an obligate, intracellular, gram-negative, tick-borne alphaproteobacterium within the genus Ehrlichia (family Anaplasmataceae), is an emerging disease in humans, domestic animals, and mice worldwide [1]. A recently recognized Ehrlichia species [3], is closely related to the canine monocytic ehrlichiosis-causing pathogen E. canis, with phylogenetic analysis revealing that this new species evolved from highly variable strains of E. canis [4]. E. minasensis can be propagated in canine macrophage-like cell lines (e.g., DH82) and Ixodes scapularis cell lines (e.g., IDE8) [5,6], and can cause clinical manifestations associated with ehrlichiosis in experimentally infected cattle [5]. Whereas other Ehrlichia species (including E. chaffeensis) and Ehrlichia-like organisms have been detected in Haemaphysalis hystricis (H. hystricis), E. minasensis has not been detected in this tick species so far [14,15]. The hard-bodied H. hystricis ( named east Asian mountain haemaphysalid), which is an obligate ectoparasite of mammals, is distributed in China, Japan, Vietnam, India, and Thailand (http://www.catalogueoflife. org/col/details/species/id/4f85d86075bf0ac2ba1e6b55d31d82be)
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