• Parasites, Hosts and Diseases
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• v.58 no.2
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• pp.195-200
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• 2020

Soil-transmitted helminths, including Ascaris lumbricoides and Trichuris trichiura, are important intestinal parasites mostly affecting younger people in developing countries. In 2014-2015, we performed mass fecal examinations targeting a total of 2,227 schoolchildren in 3 districts (South Dagon, North Dagon, and Hlaing-thar-yar) of Yangon Region, Myanmar, using the Kato-Katz thick smear technique. The egg positive children were subjected to a mass drug administration (MDA) using a single oral dose of 400 mg albendazole. The pre-treatment egg positive rate (EPG/person) of A. lumbricoides averaged 17.2% (15,532); it was 25.2% (21,796), 14.2% (11,816), and 12.8% (12,983) in 3 districts, respectively, and that of T. trichiura averaged 19.4% (1,074), and was 24.1% (1,040), 12.3% (852), and 21.2% (1,330) in 3 districts, respectively. Follow-up fecal examinations performed 4 months post-MDA revealed considerable decreases of A. lumbricoides prevalence (EPG/person) to av. 8.3% (12,429), and 13.7% (17,640), 8.0% (7,797), and 4.5% (11,849) in 3 districts, respectively. However, T. trichiura did not show any recognizable decrease in the prevalence (EPG/person) remaining at av. 18.2% (862), and 18.5% (888), 11.5% (812), and 23.3% (887) in 3 districts, respectively. The results demonstrated difficulty in short-term control of T. trichiura by MDA using albendazole and suggested necessity of either a long-term MDA (>10 years) or changing the albendazole regimen into 2~3-day course (total 800 or 1,200 mg), or using an alternative drug/drug combination.

• Restorative Dentistry and Endodontics
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• v.32 no.4
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• pp.343-355
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• 2007

The objectives of this study was to evaluate the durability of 4 resin cements by means of microtensile bond strength test combined with thermocycling method and fractographic FE-SEM analysis. Experimental groups were prepared according to thermocycling (0, 1,000, 5,000) and the kind of resin cements, those were Variolink II, Multilink, Panavia F 2.0, Rely X Unicem. Flat dentin surfaces were created on mid-coronal dentin of extracted third molars. Then fresh dentin surface was grounded with 320-grit silicon carbide abrasive papers to create uniform smear layers. Indirect composite block (Tescera, Bisco Inc., Schaumburg, IL, USA) was fabricated ($12\;{\times}\;12\;{\times}\;6\;mm^3$). It's surface for bonding to tooth was grounded with silicon carbide abrasive papers from 180- to 600-grit serially, then sandblasted witk $20\;-\;50\;{\mu}m$ alumina oxide. According to each manufacturer's instruction, dentin surface was treated and indirect composite block was luted on it using each resin cement. For Rely X Unicem, dentin surface was not treated. The bonded tooth-resin block were stored in distilled water at $37^{\circ}C$ for 24 hours. After thermocycling, the bonded tooth-resin block was sectioned occluso-gingivally to 1.0 mm thick serial slabs using all Isomet slow-speed saw (Isomet, Buehler Ltd, Lake Bluff, IL, USA). These sectioned slabs were further sectioned to $1.0\;{\times}\;1.0\;mm^2$ composite-dentin beams. The specimens were tested with universal testing machine (EZ-Test, Shimadzu, Japan) at a crosshead speed of 1.0 mm/min with maximum load of 500 N. The data was analyzed using one-way ANOVA and Duncan's multiple comparison test at $p\;{\leq}\;0.05$ level. Within the limited results, we conclude as follows; 1. The bond strength of Variolink II was evaluated the highest among experimental groups and was significantly decreased after 1,000 thermocycling (p < 0.05). 2. The bond strength of Multilink was more affected by thermocycling than the other experimental groups and significantly decreased after 1,000 thermocycling (p < 0.05). 3. Panavia F 2.0 and Rely X Unicem showed the gradually decreased tendency of microtensile bond strength according to thermocycling but there was no significant difference (p > 0.05). 4. Adhesive based-resin cements showed lower bond strength with or without thermocycling than composite based-resin cements. 5. Variolink II & Multilink showed high bond strength and mixed failure, which was occurred with a thin layer of luting resin cement before thermocycling and gradually increased adhesive failure along the dentin surface after thermocycling. The bonding performance of resin cement can be affected by application procedure and chemical composition. Composite based-resin cement showed higher bond strength and durability than adhesive based-resin cement.

• Journal of Preventive Medicine and Public Health
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• v.3 no.1
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• pp.1-16
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• 1970

The present status of control measures for public health important helminthic infections in Korea was surveyed in 1969 and the following results were obtained. The activities of parasitic examination and Ascaris treatment for the positives which were done during 1966 to 1969 were brought in poor result and could not decrease the infection rate. It is needed to improve or strengthen the activities. The mass treatment activities for paragonimiasis and clonorchiasis in the areas which were designated by the Ministry of Health were carried out during 1965 to 1968 with no good results in decrease of estimated number of the patients. There were too many pharmaceutical companies where many kinds of anthelmintics were produced. It may be better to reduce the number of anthelmintics produced and control the quality. The human feces, the most important source of helminthic infections, was generally not treated in sanitary ways because of the poor sewerage system and no sewage treatment plant in urban areas and insanitary latrines in rural areas. The field soils of 170 specimens were collected from 34 areas out of 55 urban and tourist areas where night soil has been prohibited by a regulation to be used as a fertilizer, and examined for parasites contamination with the result of Ascaris egg detection in 44%. Some kinds of vegetables of 64 specimens each from the supply agents of parasite free vegetables and general markets were collected and examined for parasites contamination with the results of Ascaris egg detection in 25% and 36% respectively. The parasite control activities and the ability of parasitological examination techniques in the health centers of the country were not satisfactory. The budget of the Ministry of Health for the parasite control was very poor. The actual expenditure needed for cellophane thick smear technique was 8 Won per a specimen. As a principle the control of helminthic infections might be led toward breaking the chain of events in the life cycle of the prasites and eliminating environmental and host factors concerned with the infections, and the following methods nay be pointed out. 1) Mass treatment might be done to eliminate human reservoirs of an infection. 2) Animal reservoirs which are related with human infections night be eliminated. 3) The excretes of reservoirs, particularly human feces, should be treated in sanitary ways by the means of sanitary sewerage system and sewage treatment plant in urban areas and sanitary latrines such as waterborne latrine, aqua privy and pit latrine in rural areas. The increase of national economical development and prohibition of the habit of using night soils as a fertilizer might be very important factors to achieve the purpose. 4) The control of vehicles and intermediate hosts might be done by the means of prohibition of soil contamination with parasites, food sanitation, insect control and snail control. 5) The improvement of insanitary attitudes and bad habits which are related with parasitic infections night be done by the means of prohibition of habit of using night soils as a fertilizer, and improving eating habits and personal hygiene. 6) Chemoprophylactic measure and vaccination may be effective to prevent the infections or the development of a parasite to adult in the bodies when the bodies were invaded by parasites. Further studies and development of this kind of measures are needed.

• Journal of agricultural medicine and community health
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• v.9 no.1
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• pp.83-108
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• 1984

Out of a total of 58 species of helminthic and protozoan parasitic infections in Korea, so far 38 species were reported as intestinal parasites of man. Quite a few species of the intestinal parasitic infections have long been prevalent throughout the country and this has been a significant public health problem. In this paper, current status and transition of the intestinal parasitic infections in the past years were presented. Chronological reviewing of data show background and prospects of change in the prevalence of infections. In the national prevalence survey on parasitic infections conducted once every five years since 1971, stool examinations were done by both cellophane thick smear and brine flotation techniques. Every egg positive case of Ascaris lumbricoides and Clonorchis sinensis was further examined by Stoll's dilution egg counting technique. In 1981, perianal swab using adhesive cellulose tape was added for Enterobius infection. For protozoan cyst examination conducted by province and city in '81, fecal specimens were fixed in SAF solution and examined by the formalin-ether concentration technique. High prevalence of parasitic infection in ana before the 1960s can be easily understood from the data given by the Ministry of Health and Social Affairs in 1967. From a parasite control point of view, the 1960s was the preparatory period particularly for control of soil-transmitted helminthiasis. Several organizations which have contributed to parasite control were founded in this period and the prevention law of parasitic infections was passed in '66. In the '70s, overall prevalence rates of the common intestinal parasitic infections, which were highly prevalent in the past were turned into reduction phase for the first time. The '80s can be said to be an active control period of parasitic infections. Intestinal helminths According to the reports of the national prevalence survey on parasitic infections, the prevalence of helminthic infections was 84.3%(number of person examined:24,887) in '71, 63.2%(27,178) in '76, and 41.1%(35,018) in '81. By area, the prevalence rate in '81 was 35.1%(20,569) in urban areas and 49.6%(14,447) in rural areas. Intestinal nematodes Ascaris lumbricoides The prevalence of Ascaris infection has decreased significantly in recent years. Among students, the prevalence was 55.4%, in '69 and decreased to 4.7% in '83. In the national prevalence surveys, the prevalence decreased to 13.0% in '81 from 54.9% in '71. By area, the prevalence decreased to 8.5% in '81 from 46.4% in '71 in urban area and 19.4% in '81 from 59.6% in '71 in rural area. By age, the prevalence has become in recent years relatively even in all age groups, although higher prevalence used to be seen in young age groups of around 10 years old, particulary in the highly prevalent rural areas. By sex, the prevalence was higher in the female than in the male. Unfertilized egg positive rates among the ascariasis cases increased gradually up to 55.4% on the average in '81. The intensity of the infection was also significantly decreased. Trichuris trichiura Trichuris infection had also decreased to 23.4% in '81 from 65.4% in '71. By area, the decreasing tendency of the prevalence became faster in urban areas than in the rural areas. The prevalence in urban and rural areas in '71 was 69.7%, and 63.1% respectively and decreased to 19.5% and 29.0% respectively in '81. By age, the prevalence reached a peak at the 10-14 age group and showed relatively even distribution throughout all age groups. By sex, the prevalence was close in young age groups, but in the 30s or over age group, especially in rural area, the prevalence was significantly higher in the female than in the male. The prevalence has much fluctuated depending in the area. The prevalence in rural areas surveyed in the '80s shows a range between 20.9% and 73.7% by locality. It is anticipated that the prevalence of Trichuris infection will drop more rapidly, when mass treatment is conducted. Hookworms Hookworm infection by mostly Ancylostoma duodenale and a few by Necator americanus has decreased to a negligible levels in recent years. In the national prevalence surveys, the prevalence was 10.7% in '71, 2.2% in '76, and 0.5% in '81. The prevalence was higher in rural areas than in urban areas. Wide application of multi-specific anthelminthics in the ascariasis control programmes conducted in the past decade appear to have been effective against hookworm infection. Trichostrongylus orientalis As in the case with hookworm infection, the prevalence of Trichostrongylus infection has reached a negligible levels. In the national prevalence surveys, the prevalence was 7.7% in '71, 1.0% in '76 and 0.2% in '81. Enterobius vermicularis In the national prevalence survey in '81, the egg positive rate was 12.0%. Higher prevalence is expected when examined repeatedly. The prevalence rate was 10.3% in urban area and 14.6% in rural area. In recent surveys conducted in rural areas among schoolchildren, the prevalence was 32.4% in Gimhae Gun in '82 and 64.1% in Yeongyang Gun in '83. By age, the egg positive rate was higher in young age groups of around 10 and sharply decreased in age groups of around 20 and then somewhat increased again in middle age groups. By sex, the prevalence was higher in the female than in the male. Strongyloides stercoralis Strongyloides stercoralis infection has rarely been found in Korea. Three cases were reported in 1914. And 0.1-0.5% were found infected out of 2,642 persons examined at the prisoner-of-war camp on Geojedo in 1956. One case was reported in '54 and '82, respectively. Anisakis spp. No systematic survey has been conducted for anisakiasis In Korea. So far, only several cases have been found 1 case in Seoul in '71, 5 cases in Busan in '81 and 1 case in Busan in '84. Intestinal trematodes Metagonimus yokogawai In the national prevalence survey conducted in 1981, the egg positive rate was 1.24% on the average. High endemic areas are located in the southwestern part of Korea. The prevalence in Hadong Gun was 29.1% on the average in '79. In a survey conducted in 76, the prevalence was 44.0% in Gwangyang, 55.0% in Gogseung and 29.0% in Gurye. The infection is closely correlated with raw sweetfish consumption in these areas. Other intestinal trematodes A human case of Heterophyes heterophyes was reported in 1914. Several species were reported in the '80s : 17 cases of Fibricola seoulensis, 9 cases of Pygidiopsis summa, 8 cases of Heterophyes heterophyes nocens, 1case of Heterophyopsis continua, 2 cases of Stellantchasmus falcatus, 1 case of Stictodora sp., 1 case of Echinostoma hortense, and 4 cases of Echinochasmus japonicus. As the intermediate hosts, snakes and frogs play a role for F.seoulensis and fish for the rest of the species. Intestinal cestodes Taenia saginata and T. solium Egg positive rates in the national prevalence survey were 0.7% in '76 and 1.1% in '81. The prevalence in '81 was 0.6% in urban area and 1.8% in rural area. The proglottid positive rate in Jeju Do was 19.2% on the average. On Udo, Jeju Do in 1983, the egg positive rate among the inhabitants was 2.9%. Hymenolepis nana In the national prevalence survey, egg positive rates were 0.6% in '76 and 0.4% in '81. No difference was seen in the prevalence by area and sex. Hymenolepis diminuta Infected cases were reported : 3 in '64 and I in '66. Egg positive rate in '81 was 0.01% in the national prevalence survey. Diphylobothrium latum So far, about 30 cases have been reported. The cases have been reported more frequently in recent surveys. Mesocestoides sp. A case was reported from a hospitalized patient in Seoul in '67. Spirometra erinacei Two cases were reported in '84 following reidentification of the adult worms collected in '74. Intestinal protozoa Out of a total of 23 species of human protozoan infections in Korea, 13 species were reported as intestinal protozoa : Entamoeba histolytica, E coli, Endolimax nana, Iodamoeba b$\ddot{u}$tschlii, Dientamoeba fragilis, Giardia lamblia, Chilomastix mesnilii, Embadomonas sp., Enteromonas hominis, Trichomonas hominis, Isospora belli, I. Hominis(Sarcocystis hominis), and Balantidium coli. Since the first report on intestinal protozoan infections in 1925, there have been quite a few survey data on the prevalence of the infection. It was found reviewing the data chronologically that up to the early '70s the infection was prevalent around a 30-50%. After that, the protozoan cyst positive rate has shown the tendency of gradual decrease throughout the country. Protozoan cyst survey conducted in Seoul and several provinces in 1981 revealed infection rates of 8.9%(1,310) in Gangweondo, 10.7%(1,703) in Gyenggi Do, 11.7%(1,032) in Jeonra Buk Do, 9.1%(4,116) in Jeonra Nam Do, and 1.4%(5,275) in Seoul. Entamoeba histolytica In the survey conducted by province in '81, the cyst positive rate was 0.8% in Gangweon-do, 0.3% in Gyeonggi Do, 1.4% in both Jeonra Buk Do and Jeonra Nam Do, and 0.2% in Seoul. Giardia lamblia In the survey by province in '81, cyst positive rates were 2.2% in both Gyeonggi Do and Jeonra Buk Do, 1.9% in Jeonra Nam Do, 0.5% in Gangweon Do, and 0.9% in Seoul. Balantidium coli Two cases were reported. One in 1930 and the other in '74. Isospora belli and I. Hominis(Sarcocystis hominis) Isospora belli was reported : 1 case in '56 and 3 cases in '66. I. Hominis, recently identified to be synonymous with Sarcocystis hominis, was reported : 3 cases in '66. Other intestinal protozoa The protozoan parasites other than the above mentioned are generally treated as commensal, although some of them are considered to be pathogenic. The data of '81 show that about 10% of the inhabitants are still infected with protozoa.