Geographical Distribution and Epidemiologic Factors of Chigger Mites on Apodemus agrarius during Autumn in Korea.

A nationwide survey of chigger mites causing scrub typhus and an investigation of epidemiologic factors for chigger mites was conducted at 16 localities in 8 provinces in Korea during autumn 2009, 2012, and 2013. A total of 233 Apodemus agrarius were captured, and all were infested with chigger mites. The chigger index was highest in Chungcheongbuk-do in 2009 (358.3) and 2012 (290.1) and Chungcheongnam-do in 2013 (294.4). The predominant chigger mite species was Leptotrombidium pallidum in the northern and central parts and L. scutellare in the southern and western parts, Korea. L. pallidum was not found in Jellanam-do and Gyeongsangnam-do and the distribution of L. scutellare had been expanded in the northern parts of Korea. The chigger index of L. pallidum was positively correlated with temperature and negatively correlated with humidity. The incidence of scrub typhus is dependent on L. scutellare index. These findings could be helpful to monitor the distribution of chigger mites and to develop a preventive measures for scrub typhus in Korea.

Indoor Occurrence of the Ghost Ant Tapinoma melanocephalum (Hymenoptera: Formicidae) in Urban Homes in Korea.

The ghost ant Tapinoma melanocephalum is a common household pest worldwide. The present study examined the occurrence of the species in urban homes in Korea. During the period of September 2014 to January 2016, T. melanocephalum workers were collected from 58 homes at 29 different localities using bait traps with 10% sugar solution. The species was widely distributed throughout urban homes at 29 different localities, and the indoor occurrence of T. melanocephalum was highest in Seoul (32.7%) and metropolitan areas of Gyeonggi-do (Province) (29.3%). The indoor incidence rate of T. melanocephalum peaked in September (22.8%), remained moderate from October through April, and peaked again in May (15.7%). In contrast, a low incidence was observed from June to August (7.0%). The present study provides evidence that native ants, such as T. melanocephalum, are potential indoor pests of homes in Korea throughout the year.

Prevalence of chigger mites and Orientia tsutsugamushi strains in northern regions of Gangwon-do, Korea.

The present study aimed to survey the prevalence of chigger mites and Orientia tsutsugamushi (O. tsutsugamushi) infection in the northern regions of Gangwon-do, Korea. From early February to early June 2015, a total of 17,050 chiggers were collected from striped field mice, Apodemus agrarius, in Cheorwon-gun, Hwacheon-gun, Yanggu-gun, and Goseong-gun, which are well-known endemic areas of scrub typhus in Korea. The chiggers were analyzed using molecular genomic methods, as previously described. Among the 7,964 identified chiggers, the predominant species was Leptotrombidium pallidum (76.9%), followed by L. zetum (16.4%), L. orientale (4.3%), L. palpale (0.3%), L. tectum (0.2%), and Neotrombicula tamiyai (1.8%). The chigger index (CI) was highest in Hwacheon (115.58), followed by Cheorwon (97.02), Yanggu (76.88), and Goseong (54.68). Out of the 79 O. tsutsugamushi-positive chigger pools, 67 (84.8%) were identified as the Boryong strain, 10 (12.7%) as the Youngworl strain, and only 2 were the Jecheon strain. Based on the high infestation of chiggers in striped field rodents and the high rate of O. tsutsugamushi infection in chigger mites, Hwacheon-gun and Cheorwon-gun are presumed to be high-risk areas for scrub typhus. Furthermore, L. pallidum, a major vector of scrub typhus, and the dominant O. tsutsugamushi serotype, the Boryong strain, were found in the northern regions of Gangwon-do, Korea.

Prevalence of pediculosis capitis among Korean children.

Pediculus humanus capitis is an ectoparasite, which causes scalp pruritus particularly among children. A total of 15,373 children including 8,018 boys and 7,355 girls from 26 primary schools and 15 kindergartens attached to the primary schools and a total of 33 children from an orphanage were examined for head lice infestation (HLI). The overall prevalence of HLI in this study was 4.1% including 3.7% of the urban areas and 4.7% of the rural areas. Head lice were found more frequently in girls than in boys with prevalence of 6.5% and 1.9%, respectively. The infestation rate by school grade was 3.2%, 4.7%, 4.2%, 5.0%, 4.9%, 3.8%, and 2.1% for kindergarten, first, second, third, fourth, fifth, and sixth grades, respectively. The infestation rate of the children in an orphanage was 66.7%. The prevalence of HLI has decreased especially in the rural areas. However, HLI is a still health problem of kindergarteners and primary schoolchildren in Korea.

Geographical distribution and relative abundance of vectors of scrub typhus in the Republic of Korea.

A survey to determine the geographical distribution and relative abundance of potential vectors of scrub typhus was conducted from October to November 2006 at 13 localities throughout the Republic of Korea. Apodemus agrarius accounted for 97.6% (80/82) of all rodents, while only 2 Myodes regulus (2/82) were collected. A total of 10,860 chiggers were collected from A. agrarius belonging to 4 genera and 8 species, while only Walchia fragilis (40) was collected from Myodes regulus. Leptotrombidium pallidum (8,137; 74.9%), a vector of scrub typhus, was the predominant species collected from A. agrarius followed by Leptotrombidium scutellare (2,057, 18.9%), Leptotrombidium palpale (279; 2.7%), Leptotrombidium orientale (232; 2.1%), and Leptotrombidium zetum (79; 0.7%), Neotrombicula tamiyai (58; 0.5%), Euschoengastica koreaensis (16; 0.1%), and Cheladonta ikaoensis (2; < 0.1%). L. pallidum was the predominant chigger collected at collection sites in Gangwon (100%), Gyeonggi (87.2%), Chungnam (100%), Chungbuk (100%), Jeonbuk (73.9%), Jeonnam (77.0%), and Gyeongbuk (66.1%) provinces, whereas L. scutellare was the predominant chigger collected in Gyeongnam province (77.9%) and Jeju Island (62.3%). Data suggest a correlation between chigger population abundance and human cases of scrub typhus in Korea.

Purification, crystallization and preliminary crystallographic characterization of the caspase-recruitment domain of human Nod1.

The caspase-recruitment domain (CARD) is known to play an important role in apoptosis and inflammation as an essential protein-protein interaction domain. The CARD of the cytosolic pathogen receptor Nod1 was overexpressed in Escherichia coli and purified by affinity chromatography and gel filtration. The purified CARD was crystallized at 277 K using the microseeding method. X-ray diffraction data were collected to 1.9 A resolution. The crystals belong to space group P3(1) or P3(2), with unit-cell parameters a = b = 79.1, c = 80.9 A. Preliminary analysis indicates that there is one dimeric CARD molecule in the asymmetric unit.

A survey on head lice infestation in Korea (2001) and the therapeutic efficacy of oral trimethoprim/sulfamethoxazole adding to lindane shampoo.

Total of 7,495 children including 3,908 boys and 3,587 girls from a kindergarten and 15 primary schools were examined for head lice infestation (HLI). The overall prevalence of HLI in this study was found to be 5.8%. Head lice were much more commonly detected in girls than in boys with prevalence of 11.2% and 0.9%, respectively. Sixty-nine children with HLI were treated with 1% lindane shampoo alone (group 1), and 45 children with HLI were treated with 1% lindane shampoo and oral trimethoprim/sulfamethoxazole (group 2), and follow-up visits were conducted 2 and 4 weeks later. The children who still had HLI 2 weeks after the primary treatment were treated again. At the 2-week follow-up visit, the treatment success rates of groups 1 and 2 were 76.8% and 86.7%, respectively, and at the 4-week follow-up visit, the rates were 91.3% and 97.8%, respectively. No statistically significant synergistic effect was observed for the combination of a 1% lindane shampoo and oral trimethoprim/sulfamethoxazole.