Nationwide Geographical and Temporal Distribution of Tick-Borne Diseases in Korean Water Deer (Hydropotes inermis argyropus)

Ticks are major vectors of numerous pathogens, and their public health significance is increasing due to climate change and the expanding involvement of wildlife hosts. In Korea, the Korean water deer (KWD, Hydropotes inermis argyropus) is widely distributed and considered a key wild host for ticks, potentially serving as a reservoir for diverse tick-borne diseases (TBDs). To examine the geographical and temporal distribution of TBDs in this species, 1035 spleen samples were collected from KWDs across 12 regions between April and November 2023. Overall, 93.6% (969) of samples were positive for at least one pathogen. Five Anaplasma species were identified: A. phagocytophilum, A. phagocytophilum-like A (APLA), APLB, A. bovis, and A. capra. In addition, Borrelia theileri and three Theileria species—T. capreoli, T. cervi, and T. luwenshuni—were detected. Notably, this study presents the first global detection of APLA, APLB, and B. theileri in KWDs. Statistically significant regional and seasonal differences in prevalence were observed, with higher detection rates in northern regions and during autumn, suggesting that environmental and ecological factors influence transmission dynamics. These findings highlight the role of KWD as a reservoir host for multiple TBDs and underscore the importance of wildlife-based surveillance for assessing zoonotic disease risks.