Long-term ecological surveillance of hard ticks (Acari: Ixodidae) and SFTSV in Dangjin, central Korea (2018-2024)

Background: Hard ticks (Ixodidae) are the primary vectors of severe fever with thrombocytopenia syndrome virus (SFTSV), a tick-borne pathogen of increasing public health concern in East Asia. Understanding local vector ecology requires long-term monitoring, particularly in regions where human cases occur but viral prevalence in ticks remains unclear. This study conducted a multi-year ecological and molecular surveillance of hard ticks and SFTSV in Dangjin-si, Chungcheongnam-do, a representative region of central Korea. Methods: From 2018 to 2024, ticks were collected monthly from April to November across four habitat types (grasslands, mountain road, mixed forest, and cemetery) using standardized 24-hour CO ₂ -baited traps. Specimens were morphologically identified and pooled by species, developmental stage, sex, and habitat. A total of 36,478 ticks were grouped into 3,106 pools. Total RNA was extracted and screened for SFTSV using nested RT-PCR, and amplification results were confirmed by agarose gel electrophoresis. Results: A total of 72,956 ticks belonging to Haemaphysalis longicornis , H. flava , and Ixodes nipponensis were collected. Haemaphysalis longicornis dominated the collection, representing 63.42% of all adult and nymphal ticks. Tick abundance peaked during 2018–2019 and was highest in grassland habitats. None of the 3,106 pools tested positive for SFTSV. Conclusions Although SFTSV was not detected, the persistently high abundance and broad ecological distribution of Haemaphysalis species suggest that Dangjin-si maintains environmental conditions that could support pathogen introduction or amplification. These long-term data provide a valuable baseline for early-warning systems and highlight the need for targeted surveillance in nearby high-incidence regions. Integrating ecological, climatic, and epidemiological data including multi-pathogen screening will be essential for strengthening One Health-based risk assessment frameworks in low-prevalence areas.