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

Abstract

The Korea Disease Control and Prevention Agency has established regional centers at 16 locations to monitor vectors and pathogens. We investigated the geographical and temporal distribution of chigger mite populations to understand tsutsugamushi disease epidemiology in 2020. To monitor weekly chigger mite populations, 3637 chigger mites were collected from sticky chigger mite traps in autumn. Chigger mites appeared from the first week of October to the third week of December, peaking in the fourth week of October. The predominant species were Leptotrombidium scutellare, Leptotrombidium palpale, Neotrombicula kwangneungensis, Neotrombicula tamiyai, and Leptotrombidium pallidum. To monitor Orientia tsutsugamushi infection in chigger mites, 50,153 chigger mites were collected from 499 trapped wild rodents in spring and autumn, with a chigger index of 100.5. Approximately 50% of chigger mites were pooled into 998 pools, and the minimum infection rate (MIR) of O. tsutsugamushi was 0.1%. Jeongeup had the highest MIR for O. tsutsugamushi (0.7%). The Kato-related genotype was the most common (52.2%), followed by the Karp-related (17.4%), Boryong (13.0%), JG-related (8.7%), Shimokoshi (4.3%), and Kawasaki (4.3%) genotypes. Ecological and geographical studies focusing on the basic ecology and pathology of mites will improve our understanding of tsutsugamushi disease risks in the Republic of Korea.

Not Only Leptotrombidium spp. an Annotated Checklist of Chigger Mites (Actinotrichida: Trombiculidae) Associated with Bacterial Pathogens

“…Orientia tsutsugamushi -positive larvae were collected from A. agrarius , the Korean red-backed vole M. regulus (Thomas, 1907) and the Ussuri white-toothed shrew Crocidura lasiura Dobson, 1890 (Mammalia: Soricomorpha) in South Korea [ 34 , 62 , 63 ].…”

“…Species individuals (also reported as Euschoengastia miyagawai ) captured with chigger traps and collected from rodents (mainly A. agrarius ) revealed the presence of O. tsutsugamushi in South Korea and some other Rickettsia species (most probably not O. tsutsugamushi ) in Japan [ 14 , 34 , 71 , 72 ].…”

“…Orientia tsutsugamushi -positive parasitic larvae were found in South Korea and Russia (Primorsky Krai). Chiggers were captured on wild animals including A. agrarius , M. regulus and C. lasiura [ 34 , 62 , 63 , 115 , 116 , 117 ].…”

“…Due to the significance of the illness, involving lethality without treatment, and its high prevalence in the endemic areas of SE Asia, the relation Leptotrombidium spp.— O. tsutsugamushi is most well explored in literature. Issues raised so far concern scrupulously investigated ecological, epidemiological, molecular and geographical aspects of the chigger-borne rickettsiosis occurrence in general as well as in particular areas of China, South Korea, Japan, Russia, Taiwan, Thailand and Asia–Australia–Pacific region, which together constitute the so called ‘tsutsugamushi triangle’ [ 10 , 14 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 ]. Recent studies, however, indicate that scrub typhus is no longer limited to the above-mentioned zone, as cases from Africa, Middle East and South America have been also reported [ 36 , 37 , 38 , 39 ].…”

Buerger’s Disease May be a Chronic Rickettsial Infection with Superimposed Thrombosis: Literature Review and Efficacy of Doxycycline in Three Patients

“…, rural areas, mountains, city parks, or riversides), occur between October and December (97.0% of the patients notified to the Korea Disease Control and Prevention Agency occurred during these two months) [ 151 ], and have eschar. In particular, because the outbreak season in humans is related to the seasonal abundance of chigger mites [ 152 153 ], occurrence of tsutsugamushi disease beyond the outbreak season is strong evidence against chigger-borne transmission. Eschar is uncommonly observed in tropical countries; however, it is common in temperate countries, such as Korea (79.0% – 93.0%) and Japan (85.0% – 87.0%) [ 154 155 156 157 ].…”