Surveillance of Chigger Mite Vectors for Tsutsugamushi Disease in the Hwaseong Area, Gyeonggi-do, Republic of Korea, 2015

Abstract

<jats:p>Owing to global climate change, the global resurgence of vector-borne infectious diseases and their potential to inflict widespread casualties among human populations has emerged as a pivotal burden on public health systems. Tsutsugamushi disease (scrub typhus) in the Republic of Korea is steadily increasing and was designated as a legal communicable disease in 1994. The disease is a mite-borne acute febrile disease most commonly contracted from October to December. In this study, we tried to determine the prevalence of tsutsugamushi disease transmitted by chigger mites living on rodents and investigated their target vector diversity, abundance, and distribution to enable the mapping of hotspots for this disease in 2015. A total of 5 species belonging to 4 genera (109 mites): Leptotrombidium scutellare 60.6%, L. pallidum 28.4% Neotrombicula tamiyai 9.2%, Euschoengastia koreaensis/0.9%), and Neoschoengastia asakawa 0.9% were collected using chigger mite collecting traps mimicking human skin odor and sticky chigger traps from April to November 2015. Chigger mites causing tsutsugamushi disease in wild rodents were also collected in Hwaseong for the zoonotic surveillance of the vector. A total of 77 rodents belonging to 3 genera: Apodemus agrarius (93.5%), Crocidura lasiura (5.2%), and Micromys minutus (1.3%) were collected in April, October, and November 2015. The most common mite was L. pallidum (46.9%), followed by L. scutellare (18.6%), and L. orientale (18.0%). However, any of the chigger mite pools collected from rodent hosts was tested positive for Orientia tsutsugamushi, the pathogen of tsutsugamushi disease, in this survey.</jats:p>

Monitoring Chigger Mites for Orientia tsutsugamushi in Field Small Mammals in Hwaseong-si, Gyeonggi-do, Korea, 2019-2020

“…These results indicated that A. agrarius was the dominant rodent host species for the surveyed chigger mites in the Hwaseong-si area. This dominancy of A. agrarius was consistent with the previously reported findings [ 18 , 19 ].…”

“…agrarius was the dominant rodent host species for the surveyed chigger mites in the Hwaseong-si area. This dominancy of A. agrarius was consistent with the previously reported findings [18,19]. In this survey, a representative number of the chigger mites (n= 3,773, approximately 50% of the total collected chigger mites) were tested due to practical difficulties associated with examining all captured 7,531 chigger mites recovered from the captured field small mammals and the PCR experiments for the detection of for the 56-kDa type-specific antigen gene from O. tsutsugamushi (Supplementary Table S1).…”

“…After transferred to microcentrifuge tubes at 4°C, the homogenates were assayed for O. tsutsugamushi . To detect O. tsutsugamushi DNA, nested PCR were performed using INNOPLEX TM TSUTSU detection kit (iNtRON Biotechnology, Seoul, Korea) with DNA samples prepared using the G-Spin TM Total DNA Extraction Kit (iNtRON Biotechnology) in accordance with the manufacturer’s instructions [ 18 , 19 ]. The primer pairs for the 56 kDa strain-specific antigen gene of O. tsutsugamushi were WJ173 (forward) 5′-CCAG GATTTAGAGCAGAG-3′, WJ174 (reverse) 5′-CGCTAGGTTT ATTAGCAT-3′ (Amplicon size 509 bp), WJ175 (nested forward) 5′-CCTCAGCCTACTATRAKKCC-3′ and WJ176 (nested reverse) 5′-AGCATTGATAAT-GCAGCAAG-ACC-3′ (amplicon size 350 bp).…”

“…The other strains from the pooled samples were OI011, Taguchi, and Shimokoshi, respectively ( Supplementary Table S1 ). Our research group previously monitored the same locations for 4 years from 2015 [ 18 , 19 ]. A total of 171 field small mammals were captured at the same location in the same months (April, October, and November), a total of 7,531 ectoparasitic chigger mites were recovered from the captured field small mammals, and a total of 3,773 collected chigger mites were subjected to PCR for the amplification of O. tsutsugamushi DNA.…”

Nationwide Incidence of Chigger Mite Populations and Molecular Detection of Orientia tsutsugamushi in the Republic of Korea, 2020

“…Generally, tsutsugamushi disease is reported in late September and peaks in November in the Republic of Korea [ 3 ]. The essential feature of this disease is that it is arthropod-mediated, maintaining the infection in nature through the association among warm-blooded animals, such as humans and small wild mammals, such as mites, with the pathogen O. tsutsugamushi [ 4 ].…”