Emergence of a Novel Ehrlichia minasensis Strain, Harboring the Major Immunogenic Glycoprotein trp36 with Unique Tandem Repeat and C-Terminal Region Sequences, in Haemaphysalis hystricis Ticks Removed from Free-Ranging Sheep in Hainan Province, China

Abstract

<i>Ehrlichia minasensis</i>, a recently described <i>Ehrlichia</i> species that is the most closely related to, but clearly distinct from, <i>Ehrlichia canis,</i> 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 <i>E. minasensis</i> in China. The purpose of this study was to explore whether <i>E. minasensis</i> is present naturally in ticks in China. Through PCR targeting of the genus-conserved <i>dsb</i> gene, <i>E. minasensis</i> DNA was detected in <i>Haemaphysalis hystricis</i> ticks removed from free-ranging sheep in Hainan Province, South China in 2017. The partial sequence of the <i>dsb</i>, <i>16S rRNA</i>, and <i>groEL</i> genes demonstrated that the Hainan strain shared 99% identity with the <i>dsb</i> gene of <i>E. minasensis</i> strain UFMG-EV (GenBank: JX629808), with the <i>16S rRNA</i> of <i>E. minasensis</i> isolate E-2650 (MH500005) and with the <i>groEL</i> gene of <i>E. minasensis</i> 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 <i>E. minasensis</i> 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 <i>E. minasensis</i> strain from Brazil, of which the sister clade contained different strains of <i>E. canis</i>. The discovery of this novel Hainan strain in <i>H. hystricis</i> ticks represents the first known natural presence of <i>E. minasensis</i> in South China, highlighting the need for its constant surveillance.