Molecular Detection of Anaplasma phagocytophilum and Ehrlichia Species in Ticks Removed from Humans in the Republic of Korea

Abstract

Human granulocytic anaplasmosis (HGA) and human monocytic ehrlichiosis (HME) are zoonotic tick-borne diseases transmitted via tick bites. To determine the state of human Anaplasma and Ehrlichia infections caused by tick bites in the Republic of Korea (ROK), we conducted a nationwide investigation of human cases of tick bites in 2020. A total of 180 ticks were obtained, comprising Haemaphysalis longicornis (70.0%), Amblyomma testudinarium (17.8%), Ixodes nipponensis (6.1%), H. flava (4.4%), and I. persulcatus (1.7%). In three cases (1.7%; 95% CI: 0.3-4.9), A. phagocytophilum was detected in Ixodes ticks using primers for Anaplasma-specific genes (16s rRNA, ankA, and msp4). Conversely, Ehrlichia sp. was only detected in H. longicornis, in two cases (1.1%; 95% CI: 0.1-4.0). To the best of our knowledge, this is the first record of Ehrlichia sp. in ticks parasitizing humans in the ROK. As concerns remain about the possibility of HGA and HME transmission, continuous monitoring and management of the pathogens and vectors are necessary.

Keywords: Anaplasma phagocytophilum; Ehrlichia sp.; Republic of Korea; human granulocytic anaplasmosis (HGA); human monocytic ehrlichiosis (HME); ticks.

Figure 1

Phylogenetic relationships for Anaplasma phagocytophilum, based on the partial nucleotide sequence of (a) Anaplasma 16S rRNA, (b) ankA, and (c) msp4 gene. The neighbor-joining method was used for constructing a phylogenetic tree. The numbers at the nodes represent the proportion of bootstrap values for the branch point. The three A. phagocytophilum-positive sequences identified in this study are indicated in bold. Reference strains of Anaplasma with the host, country of detection, and the National Center for Biotechnology Information accession numbers are also shown. Scale bars indicate sequence distances.

Figure 2

Phylogenetic relationships for Ehrlichia sp., based on the partial nucleotide sequence of (a) Ehrlichia 16S rRNA and (b) groEL gene. The neighbor-joining method was used for constructing a phylogenetic tree. The numbers at the nodes represent the proportions of bootstrap values for the branch point. The two Ehrlichia sp.-positive sequences identified in this study are indicated in bold. Reference strains of Ehrlichia with the host, country of detection, and the National Center for Biotechnology Information accession numbers are also shown. Scale bars indicate sequence distances.