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Epidemiologic characteristics of leptospiral infection in healthy population in special service and their neighboring civilians in Korea
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Joung Soon Kim, J.S Kim, Y Heo, H.W Chung, W.Y Lee, Y.C Hahn, H.G Byun, J.D Suh, H.K Chung
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Korean J Epidemiol. 1987;9(2):264-270.
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Abstract
The specific aim of this study was to provide epidemiologic information on leptospiral infection in healthy population in special service. These are considered to be the most important group in leptospirosis control not only due to the fact that they have frequent chance of exposure to the potentially dangerous environment for leptospiral infection but also the fact that an efficient preventive measure is urgently required for them.
Seven hundred and fifty six service men and 197 their civilian neighbor were subjected for the study. The study included an epidemiologic analysis of the population through interview survey and this was further supported by bacteriologic and serologic confirmatory tests.
Leptospira were isolated from the peripheral blood samples from those cases. The isolation positive rate were 0.5% of service men and 1.3% of the civilians. Percent of sereum antibody positives for microagglutination test (MAT) were varied from 8.3% of service men to 12.1% of the civilians. When the same population were subjected to the bacteridogical and serologic studies following the exposure to the time of harvesting, the percent of positives in both tests were increased 2.5 times comapared to those found in the same population before harvest season. Almost all of the bacteria positives (6/7) were found to be cases of inapparent infection. Only one out of the seven suffered from mild symptoms of leptospirosis complaining fever, conjuctival hemorrhage, headache, and nausea.
More than half (53%) of the serum samples were reacted with L. icterohemorrhagiae serovar lai and 22% with L. irterohemorrhagiae serovar copenhageni. The rests (25%) were reacted with other groups, L. bataviae, L. canicola, L. grippothyposa, L. automnalis, and L. semaranga.
none of the bacteria positives were antibody positives. The seroconversion rate following the expousre (harvest period) were 7.6% in service men and 9.3% in civilians, which were studies on month after the time.
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A study on the leptospiral strains isolated in Korea (preliminary result)
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J.S Kim, Y Heo, H.W Chung, W.Y Lee, G Baranton, E Amazouz
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Korean J Epidemiol. 1987;9(1):9-16.
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The objective of this study is to identify serovar of ten leptospiral strains isolated in Korea. Leptospirosis is one of the newly identified diseases in Korea by isolating leptospires from the patients of epidemic pulmonary hemorrhagic fever in 1984, till when the syndrome complex had been a disease of unknown etiology since 1975 epidemic. Leptospirosis is a disease of public health importance since then because of high frequency of occurrence with high fatality, particularly after flood during fruit-bearing season among farmers.
Numerous studies have been carried out including epidemiological, clinical and bacteriological studies for the new disease by researchers of various areas.
Nevertheless identification and distribution of leptospiral serovars have not been accomplished to the extent of developing prevention strategies.
This paper reports the preliminary result on the study that was conducted in the leptospires laboratory of Pasteur Institute jointly. Twenty six strains of leptospires were brought to the laboratory and studied for two months for serovar identification.
Routine and standard methods for leptospiral identification were employed and the preliminary result obtained is summarized as following:
1. The leptospiral cultures were heavily contaminated, probably due to inadequate way of transportation, and only 15 strains out of 26 were successfully cultureable by filtering through 0.22μm sized filter membrane and/or culturing the contaminated in the media with 5-flourouracil. The eleven strains that had viable leptospires but failed pure culture are available again in Seoul from stock cultures.
2. Microagglutination tests with antisera of 28 serovars revealed that one strain out of 15 tested reacted strongly(1:51200 dilution)with antisera of Icterohemorrhagiae copenhageni, Icterohemorrhagiae mwogolo and Icterhemorrhagiae wijnberg. However when the cross-agglutination absorption test was done the result showed that the strain belonged to none of these three strains.
Later we found the strain reacted most strongly with the antiserum of Icterohemorrhagiae lai of which clinical picture is similar to that of Korean leptospirosis but was not included in the 28 antisera of routine screening.
3. Another one strain on the other hand reacted with antisera of Canicola Hond Utrecht, Canicola chiffon (French local strain) and Canicola jonsis by the dilution of 1:25600 in MAT. Unfortunately the strain was lost completely so that the cross-agglutination-absorption test was not performed; the test will be done with the strain stocked in Korea.
4. None of remaining 13 strains reacted with the antisera of 28 serovars used for screening in dilution of 1:50.
5. All of these 13 strains that did not react with 28 serovars of pathogenic leptospiral strain reacted with tokyo weakly(1:100-400), suggesting the strains have common antigenic structure of leptospires in part but not tokyo serovar itself.
6. Two strains out of these 13 reacted with the antisera of saada and andamana in dilution of 1:1600-3200, which also grew well in the medium containing 8-azaguanine. The eleven strains that did not show any positive MAT reaction with 28 antisera of pathogenic leptospiral strain or ten saprophytic strains need further study.
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A study on efficiency of culture by type of medium and inoculum, and of identification by culture temperature in Leptospires isolation for epidemiological mass survey
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J.S Kim, S.S Lee, Y Heo, H.W Chung
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Korean J Epidemiol. 1986;8(2):323-329.
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This study was carried out on 37 febrile patients occurred in the endemic area of Korean hemorrhagic fever during the September 1986.
The objective of the study was to explore the most efficient method of leptospiral culture and identification by comparing different type of culture medium and different kind of inoculum as well as different culture temperature for epidemiological survey.
Fletcher’s medium containing 8% rabbit serum was compared with the newly developed medium by Lee, YUMC-5050A. This is made of MEM tissue culture medium(GIBCO) with 0.45gm Hepes buffer and 1ml 1.2% pyruvate / 50ml of the medium by adding ultra filtered(0.2μm pore size)urine of healthy person in 1:1 ratio. All media prepared were incubated in 30C incubator for 1-2 weeks to be sure that there was no contamination in the process of preparation.
Four different kind of inoculum, whold blood, serum separated solid part of blood(blood cells) and hemolyzed precipitate of blood(5000G centrifugation) were all inoculated to rabbit serum containing Fletcher’s and YUMC-5050A medium in duplicate for comparison.
Nine strains of the leptospires isolated were inoculated to the semisolid Fletcher’s medium in quadriplicate, cultured in 30°C incubator until the full grown colonies became recognizable, then the half of the culture were kept in 4°C refrigerator and the other half were kept in 30°C continuously(control) and checked morphological changes of the leptospires every six hours.
The results obtained are summarized as followings:
1) Among 37 febrill patients 32 revealed leptospires in blood culture, which suggested that most febrile patients were from the leptospiral infection.
2) The YUMC-5050A medium was more efficient for massive leptospiral culture in terms of its cost and leptospiral growth rate than the Fletcher's medium; the leptospiral culture positive rate regardless of inoculum was significantly higher in the YUMC-5050A than Fletcher, and that the YUMC-5050A was less expensive because the rabbit serum is not only expensive but also sometimes difficult to buy immediately.
3) Leptospiral culture positive rate was the highest(86.5%) when the hemolysed precipitates were inoculated among other inocula; whole blood(21.6%), serum(21.6%), blood cells(18.9%).
4) When the fully grown leptospiral culture were kept in 4°C refrigerator for 36 hours, over 95% of the bacteria formed typical spiral forms whereas the control culture kept in 30°C incubator for the same period of time showed spiral form bacteria in only about 10%.
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An epidemiological characteristic of dysentery outbreak in a rural area
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Y.H Kim, S Bang, J.S Kim, Y Heo, H.K Chung, M.Y Ahn, J.K Lee, C.I Ku, H Kim, S.M Kwon, W.H. Chang
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Korean J Epidemiol. 1986;8(2):330-336.
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In the middle of August 1986, several people in a small rural village(179 residents) had a similar disease that was characterized by watery diarhea, crampy adominal pain, fever and vomiting. On this outbreaks, local health department collected stool specimens for culture and administered antibiotics prophylactically. From ten stool cultures the Korean National Institute of Health isolated two strains of Shigella flexneri.
Even after the massive prophylactic administration of antibiotics, the occurrence of the cases did not show any change. Therefor the community health program of Soonchunhyang medical school and the health department in the area devided to conduct an epidemiological investigation jointly with the team of Seoul National University, in order to find epidemiological characteristics of the outbreak.
Followings are the results summarized:
1) Five strains of bacteria isolated and identified independently by three different institutes, two strains in Korea NIH, two strains in Seoul National University and one in local hospital, were all Shigella flexneri, which confirmed the cause of the outbreak being Shigella flexneri.
2) Incidence rate of the bacterial dysentary among 163 population in 41 households was 35%. It was not significantly different by age group and sex.
3) On the study of environmental factors such as water supply, sewer system, struction of privy, and communal dinning and etc. to explore a possible common source of infection, no such factor assciated with the outbreak was found.
4) Familial aggregation statistically examined by binomial distribution revealed strong(p< 0.005) association. Age and sex specific incidence rate of index cases was significantly high in female old aged(over 60 years of age), suggesting that the dysentery primarily spread by grand-mothers visiting around neighbours.
Thus it was concluded that this dysentery has spread insidiously in a small rural village through person-to-person transmission by intimate association between neighbours, particularly by old aged females.
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An analytic epidemiological study to test the hypothesis, Leptospirosis as the cause of epidemic pulmonary hemorrhagic fever in Korea
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J.S Kim, C.W Lee, D.K Oh, S.D In, Y.H Lee, W.H Cho, W.Y Lee, S.O Kim
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Korean J Epidemiol. 1984;6(1):8-15.
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This study was carried out to test the causal hypothesis, leptospirosis, of the epidemic pulmonary hemorrhagic fever on the outbreak occurred from the middle of September, 1984 in Korea.
The outbreak has occurred right after the group work to tie the fallen rice plants following flood just like the one that had occurred in 1975.
This particular disease characterized by fever, chill, malaise and nausea/vomiting in the begining of the onset and chest pain, hemoptysis, and dyspnea in the later stage of the illness, had been reported frequently since 1975 as a disease of unknown etiology. The disease has been occurred predominantly among farmers during the harvest season, particularly among those who worked in wet rice paddies located in montainous area without protection for abraised skin injuries. The fatality rate reported ranged from 5 to over 50%, the direct cause of death being asphyxia due to the massive pulmonary hemorrhage.
Despite the continuous research the etiologic agent of the disease has been remained unknown.
The objective of this study was to test the specific hypothesis, leptospiral infection, which was derived from the literature review on the papers published ; the clinical, pathological and epidemiological features of the disease was considered to be fitting mostly well among others to that of leptospirosis.
The patients who were admitted or have been admitted to hospital with diagnosis of epidemic pulmonary hemorrhagic fever were matched with their family members, villagers, and fellow soldiers who did not have the disease but worked in the same environment. Both groups were interviewed with a structured questionnaire and paired blood and urine specimens were collected. In order to increase the test validity one batch of the specimen was sent to KNIH laboratory and the other to the Dept. of Microbiology of Yonsei Medical School blindly for the laboratory works.
Environmental survey was also carried out on rice paddies located at mountainous site in an endemic area where the source of water for cultivation was spring water. There were innumerable rodent holes along the paddy banks with assively accumulated ears of rice plant. From these paddies about three liters of water was collected for laboratory work. Also forty five wild rodents were trapped from two endemic areas for the study.
These specimens were primarily inoculated to guinea pigs and mice for culture and then in a specific media to utilize for the serological test.
The results obtained from the study are as followings:
1. Letospiral organisms were isolated from nine patients, the water collected from rice paddies of endemic area, and seven wild rodents, all of which strains made the Koch’s postulate satisfactory.
2. The incidence rate of the disease among military service men was 2.7/1,000 person-day exposed and showed a cumulative effect of exposure; longer the duration of exposure, higher the incidence.
3. The incubation period calculated from the military service men ranged from 3-11 days and 8 days of mean incubation period when estimated from the epidemic curve.
4. KNIH laboratory reported the spiral organisms isolated were all fitted well to the description of L. interrogans icterohemorrhagiae with specific serological reaction to the known antigen, whereas the spital organisms isolated by the Dept. of Microbiology, Yonsei Medical School have left-handed tight coils even though other characteristics fits well to the description of L. interrogans.
The problem involved in the discrepancy on taxonomical aspect of the leptospiral organisms isolated between two laboratories may be settled down when the on-going studies are completed.
This is the first report on leptospirosis epidemic identified bacteriologically in Korea.
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An epidemiologic investigation of 1980 cholera epidemic with special emphasis on source and route of transmission in the area where the first case was notified
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J.S Kim, B.U No, S.Y Ahn, J.A Lee, B.J Park, C.K Chang, J.K Doo, S.S Kim, J.G Yoo, J.S Choi
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Korean J Epidemiol. 1980;2(1):26-42.
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An epidemiologic investigation on cholera epidemic was conducted from October 2 through October 8, 1980, in order to determine the source and the route of transmission in An Jwa Myon of Sin An Kun where the first cholera case was notified officially at the end of August 1980.
875 persons out of 1,608 people inhabiting in five villages of An Jwa Myon where the primary case of cholera occurred within September 5, were interviewed for their activities including travel history, foods taken, attendence to group feeding, place of purchase for a subsidiary food materials, source of drinking water and other relevant information.
Since a few evidences that cholera was imported to the area from Mok Po City were collected during the survey, medical records of 5 general hospitals of Mok Po were reviewed and 18 suspicious patients were traced for interview. Also the number of death occurred
in Mok Po population during last three years by month was obtained from the registration. These data were analysed and compared with that of previous years for the same month to estimate an excess number of patients and death due to diarrhea suspicious of cholera.
The study area An Jwa Myon is consisted of several islands, and ferry boats are the only mean of transportation between the islands and/or Mok Po City. The major industry of the islands for living is agriculture. Despite being islands there was no single member of crew engaged in foreign voyage. Daily goods are purchased and brought from Mok Po. General status of environmental sanitation, i. e., sewage, toilets, and kitchen is poor, and only limited number of households in one village are supplied with piped water. The socieconomic status is much lower than the Korean average.
The results of the investigation provided several evidences that the cholera outbreak in these islands was not the primary site in Korea but rather imported from Mok Po in where unnoticed cholera epidemic had been going on discretely from the end of July throughout August 1980. The epidemiologic study indicated that the cholera was induced to the island from Mok po through raw sharks served in a memorial ceremony on August 27 and 28, which was spoiled. The outbreak was triggered by funeral food serving on August 30, 31, and September 1 to which almost all of adult population in the vicinity were exposed, and an half of the attendants got sick. The funeral was for one of eight victims who became sick after eating raw shark at the memorial ceremony, other one, relatively serious, was admitted to a hospital in Mok po, two were treated at local clinic, and the others were either treated at drug store or at home and all recovered but one who deceased.
The sharks were presummed to be contaminated in Mok Po.
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A report on epidemiologic characteristics of 1980 cholera epidemic occurred in Korea
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J.S Kim, H.K Chung, H.C Oh, W.H Cho, B.Y Kim
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Korean J Epidemiol. 1980;2(1):43-52.
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Upon an outbreak of cholera in Jheonnam area, 1980, five members of the epidemiologic survey team were dispatched to the area by the Ministry of Health & Social Affaires in order to provide epidemiologic consultation to the local surveillance team for more effient control measures. This paper is prepared by the team based on the experiences obtained in the fields and data collected from the hospitalized patients, which is considered to be valuable to share with those responsible collegues for the future.
The major findings summarized are as follows :
1. The epidemiologic characteristics of the 1980 cholera epidemic, for instance the patten of spread, clinical pictures, distribution of cases by age and sex, secondary attack rate, rate of inapparent infection, fatality rate, and incubation period, were quite similar to that of previous El Tor cholera epidemics. The only difference was that the serotype of this epidemic was Inaba instead of Ogawa type, which had been the only serotype for all the previous epidemics in Korea.
2. Many problems that hindered an efficient prevention of the spread were analysed and discussed in detail；problems involved in reporting system, follow-up management of reported cases, delayed financial support from the central government, out-dated epidemiolgic investigation, inconsistent policy for isolation and quarantine etc.
3. Recommendations to the government including the proposal that well trained epidemiologist should be posted to each institute of health and laboratory (Provinces and cities) were made.
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An evaluation study on the Chunseong community health program
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J.S Kim, Y.S Park, J.Y Park, M.H Chung, H.W Chung, J.W Kim, D.S Kim
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Korean J Epidemiol. 1980;2(1):111-134.
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An evaluative research was carried out on Chunseong community health program by teaching staff and doctoral students taking the course “application of epidemiology in health service researches” 1980. The objectives of the study were to learn how to evaluate health programs through field practice, to make the results feed-back to the further program planning, and to provide an example of case study of evaluative research for the course.
The Chunseong community health program has been established and maintained by the School of Public Health, Seoul National University from 1972 with three objectives, namely demonstration of a model for comprehensive rural community health program, field training of health related professionals (mainly students of public health, medical, dental, and nursing schools), and conduction of researches to support the program, Since the program objectives were neither subdivided to each level (ultimate, intermediate, and immediate) nor described underlying assumptions, there was no alternatives but using the face validity and consensual validity as evaluation criteria.
The materials utilized for the study were the program records, research papers done in the program area, and several reports of the program published by the school. Also interview survey was conducted purposefully on students of public health school before and after the field practice, on patients visited the program medical clinic, on community leaders and randomly selected general population in order to evaluate the program in various aspects. The study scheme followed the principles of evaluation proposed by Suchman and Elton in terms of effort, performance, adequacy of performance, efficiency, and process.
The evaluation of the Chunseong community health program yielded the conclusion that the program has been successful to achieve its objectives according to the conclusion that the program has been successful to achieve its objectives according to the results obtained and presented in the text.
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