Diversity and genotypic analysis of tick-borne pathogens carried by ticks infesting horses in Korea

Ticks account for an extensive range of health and welfare issues in horses. In addition, tick-borne pathogens (TBPs) limit global animal trading and equine sporting events. Here, we assess the prevalence, co-infectivity and risk factors of TBPs in horse ticks in Korea. A total of 245 hard ticks, including 103 male and 142 female adults, were obtained from horses on Jeju Island during the spring to autumn seasons of 2013-2019. All collected ticks were identified as adultHaemaphysalis longicornis. We screened and analyzed each tick for the presence of several TBPs by polymerase chain reaction (PCR) analysis. Among the 245 ticks, we detected genes for three TBPs,CandidatusRickettsia longicornii (22.9%),Ehrlichia canis(0.4%) andTheileria luwenshuni(0.4%), whileAnaplasmaspp. was not detected. TBPs were most prevalent in ticks harvested during the autumn season, and more abundant in the female than male adults. This is the first report of the generaEhrlichia,RickettsiaandTheileriain horse ticks in Korea. TBPs in horse ticks are likely a reservoir for zoonotic transmission to other animals, including humans. Our findings demonstrate the need for further understanding of the prevalence and epidemiology of TBPs in wild and domestic animals.