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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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Epidemiologic characteristics of leptospirosis and febrile disease in population in special service at high risk of infection
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Joung Soon Kim, Yong Heo, H.W Chung, W.Y Lee, H.G Byun, J.D Suh, C.M Sung, M.Y Ahn, J.M Choi, S.J Lee, Y.C Hahn
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Korean J Epidemiol. 1987;9(2):278-287.
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This is a part of serial works on leptospirosis. In this study, a correct characterization of all of the hemorrhagic disease accompanying high fever which might be caused by various agents such as leptospira, rickettsia, viruses, and others if any was attempted by classifying the symptoms and identifing the etiologic agent which is responsible for the cases. And also serologic studies along with fundamental epidemiologic investigation on the clinical signs of the patients selected from the study area were done to draw a comprehensive conclusion.
The specific aim which is the major focus of this part of study is to find out prevalence rate of true leptospira patients among patients with high fever and to characterize the clinical pictures, such as clinical signs and symptoms, which might be specific for the true cases of leptospiral infection which is confirmed by bacterial isolation from the cases.
One hundred and nineteen patients hospitalized because of high fever (more than 38°C) for more than 24 hours were studied during 10 month (Aug., 1986-May 1987).
The findings are summarized as follows;
1) At the time of admission, leptospira isolation rate was 5.8% (6/103) and this became 13.7% (7/44, average 8.4%) after one week of hospitalization.
2) The serum samples were testeded for the presence of the antibodies specific to 22 different servar in which 3 strains isolated in this laboratory from human blood employing microagglutination tests.
The positive rate was 34.9% when the first blood samples which were collected at the time of admission tested. And it became 50.9% when the second samples were tested one after the first.
The antibody conversion rate within one week was 32.4%. Only one out of 16 cases who were antibody positive at the first test was found to be negatively converted.
When these were grouped by their antibody titer, 83.7% of whole antibody positive samples (64) demonstrated antibody titer 1.400 or lower and only 3.1% of them demonstrated higher than 1:3200.
3) Significantly higher positive rate were found when the sera were tested with the fresh strains isolated from that area.
The majority (32.4%) of the sera from Chullwon area positively reacted with locally isolated L. icterhemorrhagiae lai and 17.1% of sera from Yangoo area with locally isollated L. canicola.
In Chullwon area, 65% of the serum samples were identified belonging to 3 serovars, L. icterohemorrhagiae lai (32.4%), L. canicola (14.7%), and L. ictervhemorrhagiae copenhageni (17.6%).
In Yangoo area, 54% of the scrum samples were positive for 4 serovars, L. icterohemorrhagiae lai (14.6%), L. hebdomadis (12.2%), L. icterohemorrhagiae copenhageni (9.8%) and above mentioned local isolate.
4) among 92 patients with high fever 19 cases (20.2%) were confirmed to be leptospiral infection by the both tests for bacterial isolation and serology. Sixteen cases (16%) were the suspicious cases of leptospirosis. The rest of them, 60 patients (63.8%) were found to be uninfected with the bacteria.
5) When the seasonal changes of incidence of the feverrile disease were comparatively analyzed, the cases belonged to confirmed as leptospirosis occured maily in Autumn whereas the others occured throughout the year except the spring in which time a slight decreased cases were recorded.
The incidence of the confirmed cases were higher in groups which had been exposed to field trainings.
Sore throat, runny nose, hematemesis, and muscle pain were found to be significantly frequent signs complained by the confirmed cases and diastolic blood pressure of the cases was higher.
6) amomg the confirmed cases only 5.3% of them were primarily diagnosed as leptospirosis and majority were diagnosed as fever with unknown reason (47.3%) when they were adimitted because of the high fever. Whereas among the cases confirmed as uninfected 25% was fever with unknown reason and 46.7% for the others. The proportion of cases diagnosed as leptospirosis was 5.0%.
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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 leptospiral infection among healthy young men, a special group by leptospira isolation from blood culture in an endemic area of Korean hemorrhagic fever
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Joung Soon Kim, H.K Chung, H.W Chung, S.S Lee, J.K Kim, W.Y Lee, H.K Byun
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Korean J Epidemiol. 1986;8(1):174-181.
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This study was carried out on special groups consisted of homogeneous healthy and young Korean males stationed middle part of Korea, in order to understand the magnitude of subclinical leptospiral infection among these special groups and particularly the reationship between leptospirosis and Korean hemorrhagic fever that have shown similarity in many aspects.
One hundred eighteen subjects from the well-known endemic area of KHF and 406 subjects from non-endemic area were interviewed for the information on their behavior and environments exposed for the last one month on weekly basis; all study subjects were blood drawn for leptospira isolation by culture in newly developed media, YUMC-5050.
From the vicinity of stations studied 25 rats were captured alive, anesthesized with ether and autopsied. Lungs, liver and kidney were sectioned with a sharp scalpel and touch printed on slide glasses. These specimens were stained by IF techeique and examined for the presence of leptospiral bacteria.
Summarized results of the study are as followings：
1) The overall leptospira culture positive rate was 2.8% that was much lower than that of Korean healthy rural farmers(16%).
2) Twelve out of 15 leptospira positives were followed up to 2 months by re-culturing their blood and found none of them remained positive.
3) Leptospira culture positive rate was 9 times higher among the groups stationed in KHF endemic area(9.3%) than those stationed in non-endemic area
4) The leptospira positive status did not have any statistical correlation with the variables such as the length of stay in current station, former residence area and educational level
5) The behavioral and environmental characteristics also failed to reveal any statistical association with the leptospiral positive status
6) Clinical symptoms and signs experienced during the last one month were more frequent and various among leptospira negatives than among positives
7) Nineteen Rattus norvegicus and Rattus rattus examined by organ touch printed specimens with IF technique showed leptospira positive in 24 rats, 96% positive rate; 22 rats had leptospira in all three organs, one in kidney and liver, and the other one only in kidney
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An epidemiological study on subclinical Leptospiral infection among rural Koreans by Leptospira isolation in blood culture
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Joung Soon Kim, J.K Lee, H.W Chung, S.J Yang, H.S Lim, W.Y Lee
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Korean J Epidemiol. 1985;7(2):253-258.
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A clinical syndrome complex that had been known as epidemic pulmonary hemorrhagic fever in Korea since 1975 has been proved to be leptospiral infection by Kim et al. in 1984.
Even though hundreds of cases have been reported for the last 10 years, few information on the status of leptospiral infection among general population at risk is available.
This study was carried out in a small rural community with 189 population in 41 household to estimate subclinical leptospiral infection rate. The study consisted of interview, medical examination by doctors, and blood sampling. The first study in which only 50 inhabitants completed the study on November 3rd, and the second one for the drop-outs on December 17th, 1985.
The blood specimens were inoculated to a newly developed artificial media by Lee, YUMC-5050, which had been demonstrated to be quite sensitive, silver stained in two weeks of culture and examined under microscope for the characteristic leptospiral bacteria. Since leptospiral positives were found only among the first study group, probably due to the optimal timing for culture (November 3rd), but none of 40 specimens sampled in the second study was culture positive, the data analysis had to be depended upon the first study population. Among six positives re-cultured in the second study period, only one remained positive and five became negative within one and half month.
The summarized findings are as followings：
1) Leptospira culture positive rate was 16% average; 23% for males and 11% for females. The cases were net clustered to any particular age group but rather even for all active ages. Protective immunity for older ages was not evidenced.
2) Clinical symptoms and signs experienced by the study subjects during the last one month were not significantly different in kind and frequency between leptospira positives and negatives except one case each for hematuria and lymphadenpathy in positive group. Two out of eight positives had mild clinical manifestation competible to leptospiral infection but six of them were typical of subclinical infection.
3) Enviromental factors exposed also were not different between leptospira culture positives and negative, probably owing to the fact that these farmers were exposed to all environments in multiplicity making it difficult to find out the difference for any environmental particulars.
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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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