[Surveillance of Chigger Mites in the Republic of Korea, 2023]

Scrub typhus is one of the oldest mediator infectious diseases worldwide. It is a typical acute febrile disease that occurs in the fall. Scrub typhus is caused by the infiltration of bacteria during the ingestion of body fluids by the larvae of chigger mites with Orientia tsutsugamushi. Various symptoms, such as headaches, rashes, and fever, appear after a short incubation period. From August 31, 2023, to December 20, 2023, 18 locations across the country used chigger collectors every week to monitor the occurrence of chiggers, and the density of chiggers was compared and analyzed by converting them to the trap index, the average number of collected individuals per trap. The cumulative trap index of chigger mites collected during the 2023 monitoring period was 13.52, an increase of approximately 27.8% from 10.58 in 2022. The period of increased occurrence was approximately two weeks earlier than that in 2022. A gradual decrease was noted after the peak occurrence period at week 43; a slight increase occurred in week 50 and then decreased. This phenomenon was found to be closely related to temperature. A total of 4,863 chigger mites were collected, with 18 species belonging to five genera. Among these, Leptotrombidium scutellare was identified as the dominant species (i.e., 1,831; 37.7%). Recently, the aging rural population and increased outdoor activities have increased the likelihood of patient emergence; therefore, adhering to prevention rules and receiving an early diagnosis are important. Continuous surveillance is necessary because mediator-transmitted diseases tend to spread owing to globalization and climate change.