Population dynamics of hard ticks (Acari: Ixodidae) and their harboring rates of Severe Fever with Thrombocytopenia Syndrome (SFTS) virus in four landscapes of Gyeonggi Province, South Korea

Population dynamics of hard ticks and their harboring rates of fatal severe fever with thrombocytopenia syndrome (SFTS) were monitored from 2021 to 2022 in Gyeonggi-do, South Korea. Hard ticks were surveyed monthly using CO2-bait traps in four vegetation types, including grassland, grave, mountain trail, and shrub. From the 2-year monitoring, totals of 5,737 and 14,298 hard ticks were collected in 2021 and 2022, respectively, all of which belonged to the genus Haemaphysalis. Of these collected ticks, 97.9 and 98.3% of adults and nymphs were identified as Haemaphysalis longicornis. Generally, density peaks of H. longicornis nymphs and adults were observed from April to May and from June to July, respectively. For Haemaphysalis flava, adults showed density peaks in September, whereas no obvious seasonal patterns were observed for nymphs. The density peak of Haemaphysalis larvae was observed in August and September, followed by a density peak of adults. There was a large variation in the number of hard ticks collected among the four vegetation types, yielding no significant difference among them over the 2-year monitoring. Half of the collected ticks from each vegetation type were pooled into groups by species and developmental stage and subjected to analysis of SFTS virus harboring rates, which yielded no SFTS positive pool detected over the 2-year monitoring.