Abstract
Wild rodents act as crucial reservoir hosts for various tick-borne pathogens, such as Anaplasma phagocytophilum and Neoehrlichia mikurensis, which are responsible for the emergence of zoonotic diseases in humans. While tick-borne pathogens have been examined in various animal species, the genetic diversities present in wild rodents and their ectoparasites remain poorly understood. This study examined the prevalence and genetic characteristics of A. phagocytophilum and N. mikurensis in wild rodents, mites, and ticks from South Korea. PCR amplification and sequencing of the 16S rRNA, msp4, and groEL genes were performed to genotype A. phagocytophilum (16S rRNA and msp4) and N. mikurensis (16S rRNA and groEL). A. phagocytophilum was identified in 25.8 % of rodents and in ixodid ticks collected from rodents, with a minimum infection rate (MIR) of 2.8 %. A. phagocytophilum was detected in mites (MIR: 0.4 %) from rodents, indicating their potential role in pathogen circulation. Of the 461 wild rodents included in this study, five (1.1 %) tested positive for N. mikurensis. Furthermore, one positive pool was identified in Ixodes nipponensis nymphs (MIR: 0.1 %), representing the first documented occurrence of N. mikurensis in ticks in South Korea. Phylogenetic analysis indicated that the A. phagocytophilum sequences obtained in this study cluster with sequences from South Korea and China associated with rodents or I. nipponensis, while remaining distinct from those of European origin. The N. mikurensis sequences clustered with East Asian strains, forming two distinct groups separate from European lineages. These findings corroborate the hypothesis that wild rodents and their ectoparasites play a role in the natural maintenance and transmission of A. phagocytophilum and N. mikurensis in South Korea. Given the growing acknowledgment of these pathogens as emerging threats to human health, continued surveillance and molecular characterization are essential to understand their regional distribution and implications for public health.