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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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Abstract
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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Abstract
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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A study on health impact of a river pollution neighboring industrialized big city on the rural people residing along the river
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Joung Soon Kim, Seung Wook Lee, H.S Yoon, Y Heo, S.J Yang, T.W Ha, H.K Hong, Y.W Lee, H.H Kwon, D.H Lee, H.C Kim
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Korean J Epidemiol. 1986;8(1):37-95.
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This study is conducted to identify any adverse health impact for the rural residents living along a certain river in Korea. The river actually accomodates all the industriral and domestic waste-water discharged from its neighboring big city. Unfortunately, the river is being served for farming water residents, while the current water cleaning system does not function satisfactorily. It means a possibility that the polluted water can contaminate underground water which is the main source of drinking water in the area.
The aim of the study is to determine the contamination level of heavy metals and evaluate the health impact of the residents with a linkage to the river pollution. The study is proceeded under the following steps.
1) The area is divided into two parts where the water is used for the farming or not. They formed study and control area. For the residents within the sites, study and control groups were formed.
2) Between the two, any statistical significance was pursued for the following items,
(1) the contamination levels by the metals in drinking water source, soil, farming products, farming products, and fishes which live in the water where the river joins the main river,
(2) the contamination levels of rural residents, blood samples, and
(3) by physicians the health evaluation results by clinical and pathological tests for the residents.
3) the correlation between the blood contamination levels and the health results,
4) the correlation between the blood and environmental pollution levels were studied.
In spite of several limitations from the nature of the study,
The findings were summarized as follows：
1) No statistical significance was found in the differences between the groups with regard to age, sex, occupation, economic status, education levels, pregnancy history, number of household members, and medical insurance status.
2) No statistical significance were found with regard to smoking habit, proportions of drinking, boiled water, number of days using pesticides and number of pregnancy poisoning, frequency of monthly meat intake. But a significance was found in the number of fish intake, while almost nobody took fishes from the river.
3) Most of the residents(93%) think the river is harmful to their health and 34% among them addressed that the river contamination is the cause of various dermatitis.
4) Stillbirth rate was significantly higher in the study group, but no correlation was found with the metal contamination.
5) The study group showed significantly higher complaints for 24 symptoms believed to appear with metal contamination, but no correlation was found. No correlation was found when the symptoms are grouped into 17 disease classification, either.
6) Neurological symptoms and clinical screening tests did not show any significant difference between the groups. Past disease history showed the same thing.
7) The results of diagnoses by physicians are classified into three groups from normal to abnormal. The control groups had higher proportion of the normal, but conjunctiva abnormaly, unspecified digestive ulcer, symptoms of abdomen and pelvic area, gasritis and duodenum inflammation were more frequent in the control group. Neurologic findings by a specialist did not show any difference.
8) The values of laboratory tests for hematopoietic system, kidney, and liver functions as indices of health measurements didn’t show any significance.
9) For the level of heavy metal contamination in blood, those of Cu, Cd, Pb but Zn were statistically higher than those determined by the National Envoronmental Protection Institute for the Yang-pyong-kun residents. For Pb, Zn, Ni at 0.1% and Hg at 5%, the values from the control groups was rather higher than those in the study group. However, at was seen that the level of Cd of the study group was higher than the control groups at 5%. They failed to show any consistent pattern, but the males has higher value than the females for Cd, Zn, Hg and lower value for Cu, Pb with statistical significance.
10) The proportions of residents above the permissible levels for the metal contamination were determined. The proportions for Pb and Zn showed that those for the control group were statistically higher than those for the study group. They were 42.3% for Pb and 6.3% for Zn, respectively, in the control group. For the case group, they were 19.3% for Pb and 4.6% for Mn, respectively. The proportions of residents who had abnormal level for more than 2 kinds of heavy meatals was 10.2% and for more than 3 kinds 0.8%.
11) The health evaluation results were linked with the classification of metal levels into the normal and abnormal groups. The abnormal group in Mn level seemed to have high proportion of lassitude, but its reliability was very low because of the sample size of 1. Also, the proportion of no symptoms was significantly higher in the group abnormally contaminated by Pb and Zn rather in the normal group.
The clinical evaluation results showed that the Pb-and Zn-high groups had more frequently hearing difficulty, the Pb-high conjuntictiva problem, the Zn-high group neurotoxic disturbance and hearing difficulty. The neurological findings showed that inflammation, neurotoxic disturbance and hearing difficulty in the Mn-and Pb-high group, respectively. Also, various pathological tests did not show any significance.
12) The water quality was examined for the river and drinking water. The river seemed to be polluted by not heavy metal but various organic materials. This can be backed up by high levels of COD, BOD, and DO. The drinking water classified into underground water, well and simple-lined pump didn’t bear any significant difference from that in the control area and was believed to be generally appropriate for drinking. In the simple-lined pump and well water, the levels of Cu, Pb, and Ni were slightly higher than in the foot site river. It needs further attention to find Hg, As, Cr in the well water which did not exist in the river.
13) The sample of fishes to determine heavy metal contamination level was taken in the main river around the various sites where the river joins. While the site difference couldn’t be identified because of the fish morbidity, the levels were below being serious. However, the levels of Pb and Hg were slightly higher but not significant.
14) For the farmig product, nine crops sampled. The levels of Pb and Zn were significantly higher in brown rice, corns, garlics, while the others were below the permissible level. This results are consistent with the residents results But no significance were found when compared to the control area, while some metals show higher levels in the contral area.
15) The metal contaminatin levels in the soil of the study area were significantly higher for Pb, Zn and Mn. Although the Mn level in the residents blood is very low, the high levels for of Pb and Zn need attention beeanse they were also high in the crops.
16) The correlation between the soil and crops did not show any consistent pattern. However, in certain sites, the high correlations were found and suspected due to the confounding factors such as the regional nature of soil contamination, pesticides and fertilizer.
17) For the corelation between the blood and environmental contaminations, the levels of metals except Mn which showed the high levels in the soil and crops were also high in the blood. The relatively great portion of the residetns with high levels can cause serious health impact. However, the origin of their contamination seems to come from the soil not from the river. It deserves a further investigation on this matter.
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