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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.

The study examined the seasonal pattern of larvae, nymph, and adult life stages for Haemaphysalis longicornis and the rate of infection with severe fever from the thrombocytopenia syndrome virus in ticks collected from 12 sections (Jichukdong), 14 sections (Uldaeri), and 18 sections (Howondong) in Bukhansan dullegil for April–October 2019. Haemaphysalis longicornis ticks have been considered the main vector for severe fever with thrombocytopenia syndrome (SFTS). Haemaphysalis flava and Ixodes nipponensis were collected using the dragging and flagging method. The ratios of Haemaphysalis longicornis of the collected ticks were 91% (Jichukdong), 94% (Uldaeri), and 98% (Howondong). Monthly distributional studies of Haemaphysalis longicornis based on the developmental stage showed that the adults peaked in September while nymphs were collected more frequently from April through June. The larvae peaked in September and October. SFTS virus detection was performed using 2 × OneStep RT-PCR and nested PCR. On the other hand, no SFTS virus-specific gene was detected in 1,158 ticks of Haemaphysalis longicornis. This result provides estimates of the population densities for the life stages of Haemaphysalis longicornis and the associated disease risk in Bukhansan dullegil, where many people have visited since opening in 2010.

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.

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.

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.

To determine whether pathogenicAcanthamoeba culbertsonitrophozoites and lysate can induce cytopathic changes in primary-culture microglial cells, morphological changes were observed by transmission electron microscopy (TEM). In addition, the secretion of two kinds of cytokines, tumor necrosis factor alpha (TNF-α) and interleukin-1β (IL-1β), from microglial cells was observed. Trophozoites of pathogenicA. culbertsonimade contact with microglial cells and produced digipodia. TEM revealed that microglial cells cocultured with amoebic trophozoites underwent a necrotic process, accompanied by lysis of the cell membrane. TEM of microglial cells cocultured with amoebic lysate showed that the membranes of the small cytoplasmic vacuoles as well as the cell membrane were lysed. The amounts of TNF-α secreted from microglial cells cocultured withA. culbertsonitrophozoites or lysate increased at 6 h of incubation. The amounts of IL-1β secreted from microglial cells cocultured withA. culbertsonitrophozoites at 6 h of incubation was similar to those secreted from the control group, but the amounts decreased during cultivation withA. culbertsonilysate. These results suggest that pathogenicA. culbertsoniinduces the cytopathic effects in primary-culture rat microglial cells, with the effects characterized by necrosis of microglial cells and changes in levels of secretion of TNF-α and IL-1β from microglial cells.

Monoclonal antibodies (Mabs) were produced against crude scolex extract of T. solium metacestodes, and applied to ELISA-inhibition test for improving the specificity of serodiagnosis of human cysticercosis. Four hybridomas secreting species-specific anticysticercal Mabs (Cya-1, Cya-7, Cya-28 and Cya-31) were selected. Each Mab reacted on antigenic components of 25.5 kDa (Cya-1), 28 kDa (Cya-7), 87.5 kDa (Cya-28), and 12.5 kDa (Cya-31). IFA showed that Cya-1 was located at the calcium corpuscles, and Cya-7 at the loose connective tissue of T. solium metacestode scolex. Cya-28 and Cya-31 reacted on the tegument of the scolex. By conventional ELISA, 23 out of 28 (82.1%) cysticercosis patients were found serologically positive, but 1 out of 9 (11.1%) sparganosis cases and 6 out of 31 (19.4%) paragonimiasis cases showed false positives. By ELISA-inhibition test using species-specific anti-cysticercal Mab Cya-7, 19 out of 28 (67.9%) cysticercosis cases were found serologically positive, but there were no false positives in other parasitic infections.

ELISA-inhibition test using Paragonimus westermani specific monoclonal antibody (Mab) was investigated to improve the diagnostic specificity of paragonimiasis. By cell fusion, one hybridoma clone secreting anti-P. westermani specific Mab was selected (Pwa-14), which reacted on bands of 28 kDa, 42.5 kDa, 89 kDa and 120.5 kDa. IFA showed Pwa-14 was located at the vitelline follicles. By micro-ELISA, 100% of 22 paragonimiasis cases were found positive, but 5 of 40 clonorchiasis cases (12.5%), 3 of 26 cysticercosis cases (7.7%) showed false positive. None of 10 sparganosis patients or 28 normal controls reacted positively. On the other hand, by ELISA-inhibition test using a P. westermani specific Mab, 100% of paragonimiasis cases were found positive, and there were no positive in cysticercosis, sparganosis cases or normal controls, except 2 (5.0%) false-positive sera of 40 clonorchiasis cases. The ELISA-inhibition test using a Mab showed higher specificity in comparison with micro-ELISA for serodiagnosis of human paragonimiasis.

The enzyme-linked immunosorbent assay (ELISA)-inhibition test using a Clonorchis sinensis species-specific mouse monoclonal antibody (MAb), CsHyb 0605-23, showed increased specificity over the conventional ELISA used for serodiagnosis of clonorchiasis. To characterize the corresponding antigen further, the MAb was tested against polysaccharide, protein and glycolipid fractions obtained from a crude extract of C. sinensis adult worms, using chloroform, methanol and phenol extractions. Only the polysaccharide fraction was recognized by the MAb among those fractions. Mild oxidation of the antigen with sodium periodate showed decreased reactivity against the MAb. We concluded that the antigen and antigenic determinants recognized by the MAb are carbohydrates.

A mass treatment of head louse infestation with Sumithrin powder (0.4% phenothrin) in primary school children was implemented during the period of September 1991-May 1992. The infestation rate of total 2,515 children was 38.6% in average (21.2% in boys and 57.2% in girls). The reduction rate of head louse infestation was 93.4% with a single treatment and 94.8% with double consecutive treatments with about 10 days interval, which indicated that a single treatment would be recommended for the mass treatment in the community. Long term follow-up after Sumithrin powder application for head louse control in a primary school showed that the infestation rate dropped from 33.1% before treatment to 5.4% by seven months after treatment, giving a 83.4% reduction rate.