Bull. Org. mond. Sante' 1959, 21, Bull. Wld Hlth Org. 721-726

Clonorchiasis and in the Republic of Korea Report on a Prevalence Survey using Intradermal Tests

BRYCE C. WALTON 1 & IL CHYU 2

Until recently, information on the distribution of and prevalence of infection with the , , and the lung fluke, westermani, was based almost entirely on surveys by stool or sputum examination, involving techniques insuf- ficiently sensitive and too costly and time-consuming to allow of really adequate coverage. However, a simple and reliable intradermal test for these infections has now been developed, based on the use ofpurified antigens, and this has been used in a survey of nearly 10 000 persons in the Republic of Korea. The results show that the spread of these infections is much wider than had previously been thought. It is estimated that in South Korea alone some 4.5 million people are infected with and up to 1.5 million with para- gonimiasis-a public health problem of considerable magnitude.

Clonorchis sinensis has long been recognized as in the US Army's 406th Medical General Laboratory being highly endemic in the Naktong, Kum, Nam, (Sadun, Walton et al., 1959; Sadun, Buck & Walton, Sumgin, and Han river valleys and has been con- 1959). This test has proved to be a reliable tool for sidered to be the principal cause of the many cases epidemiological investigations in a preliminary sur- of liver cirrhosis in Korea (Crane et al., 1955). vey in Korea (Sadun, Buck et al., 1959). Because of Paragonimus westermani has been reported to be its simplicity, ease of application, and low cost, this endemic in small scattered areas throughout the method was selected as the most practical means country, and although it is much less widely dis- of testing a large population sample, and was used tributed than the liver fluke, its prevalence and for this survey carried out under the joint auspices serious effects make it a public health problem of of the Ministry of Health and Social Affairs of the serious proportions. Republic of Korea and the WHO Regional Office Previous information on the distribution of pre- for the Western Pacific. valence of infection with these two parasites has been based on surveys by stool or sputum examination. DESCRIPTION OF LOCALITIES AND SELECTION With these techniques, the recovery of P. westermani OF SAMPLES eggs is difficult and often impossible. In addition, The Republic of Korea, with a population of the techniques are expensive and time-consuming. over 21 500 000, is divided into nine provinces. Therefore, such surveys have been too limited in With the exception of the island province of Cheju either geographical coverage or number of persons Do off the southern tip of the peninsula, all pro- examined to provide an adequate basis for evalua- vinces contain some elements of the six extensive tion of the situation in regard to these parasites. river systems which cover the major portion of the Recently, an intradermal test for these infections country. Except for the narrow strip of land to the by the use of purified antigens has been developed east of the high spine of the coastal range, which 1 Captain, Medical Service Corps, US Army; Chief, extends along the entire eastern coast, the country Parasitology Division, Third US Army Medical Laboratory, is characterized by wide, flat-bottomed valleys Fort McPherson, Ga., USA; Consultant, WHO Regional with meandering streams. Office for the Western Pacific. Localities for the skin testing were selected in 2 Chief, Department of Parasitology, National Institute of Health, Seoul, Republic of Korea eight of the nine provinces and included both areas

842 -721- 722 B. C. WALTON & I. CHYU

FIG. I IL le 0 LO N rl O m 0 LOCALITIES IN REPUBLIC OF KOREA SURVEYED W UZ _- O CN _1 O CQw + n aa _- M _ r- O cm co FOR CLONORCHIASIS AND PARAGONIMIASIS v- _- _r _ _- _

- ll ls-

- 000 0 0 _- f- 0 CD C lit 00 00 1 04 t r1- 0o 0 IL 04 04 t 04 v co q v 10 CD

O '-'-( 04 lq (0o 0000co 0co CD (0(0(0(001O0O1O 01 z

0:0 + _ _0010 04 01 0 IL N'-_-_C0_0CV- + 04 z x LO Co (0 C - (0W CD 0 W(0D

4toLO co co4 L 04 co X 00 1004U qt C 00 001 ?) OIL 01 _ - 10 - W 01 01° 0 -0c 4(010 40 cm (01004 c - X CO WM - UM t Ct0eQo 0) to ( 0 z C known to be endemic and areas from which the rc 01 _ Mt- 01- 0 0 ( 1 0 Ministry of Health had no information regarding 0 010 the prevalence of these diseases. The areas chosen U C) L0) 004 00 co010 C ( O L _0 C> W W ( D f010_C 04 (Fig. 1) included localities on small tributaries or 0 01 away from streams, as well as some in major river uJ basins. A total of 7085 persons were tested in this 0. series. In addition, 2686 persons tested in two 04 10)0000- r~- 010C U) provinces during a prior co-operative study by the z ILu o LO_ - (0- O c e 406th Medical General Laboratory and the German 0 Red Cross Hospital are included. These data are 040 co 01041010rOle - were _1 v01(004(0000(00101(D OD 01 t 0o(0 0 completely comparable, since they obtained _CY 0C4Wc 4 c a- o le C4 co C~~~~~~~~~~4co with the same antigens and methods. However, it 0 IL should be pointed out that the earlier study was designed to evaluate the and no attempt 0 IL '- ' co ' 04 CD antigens, z was made to select a representative sample of the 0 10~ ~ ~ ~ ~ 4 population as to sex and age-group. The distribu- 004000Z 1°0000 W 04 L B s t048 CD.WOWF tion by province, sex, and age-group of the total co 10 01 _00 CD t 100 00 Co population tested is presented in Table 1. Although I- t 0 00 IL (0 CD (0011010 an adequate sampling was obtained for both sexes, the number of males tested was consistently greater. ~ 0~ 0- (00 0 Comparable samples were obtained in all provinces, -J |~~~~~~~~~~~~~1 to with the exceptions of Kyonggi Do, where fewer UL O 0 0 0 0 0 0 0 0 I- persons were reached because of transport difficul-

0 0 0 0 0 0 0 0 0 ties, and Kyong Sang Nam Do, where a larger _- population group was tested in the prior antigen O O 0 0 evaluation study. The age distribution was essen- 00 0 tially uniform with the exception of the 0-5-year 0 U group. This group cannot be considered typical, C 01 CM Z since it a small of o C 0 0 C E -a represents very number children E0 =C .C0 0 .~ (L 0 selected from an area highly endemic for clonor- C 0 C C c c _ chiasis in an effort to determine 0 cC U 0 0 0 z possible familial >. 0 .C sC >. >. sC YYUUYYUUUs7 sC relationships of the infection. CLONORCHIASIS AND PARAGONIMIASIS IN KOREA 723

MATERIAL AND METHODS tions with C. sinensis and some double infections might be missed. A few individuals (63) showed The antigens for the intradermal tests were acid- identical-sized wheals from the two antigens. These soluble protein fractions of whole worm prepara- were interpreted as double infections. tions obtained by Melcher fractionation, and the methods were those reported by Sadun, Buck & Clonorchiasis Walton (1959) and Sadun, Walton et al. (1959). As indicated in Table 2 and Fig. 2, positive The antigens were standardized to contain approxi- reactions to C. sinensis antigen were obtained in all mately 10 mg of protein per 100 ml. All individuals provinces, with the highest percentages occurring were given intradermally, on the volar surface of the in Kyong Sang Puk To, where 53% of all males same arm, P. westermani antigen, C. sinensis antigen, and 14 % of all females tested gave positive reactions. and a buffered saline Merthiolate (thiomersal) con- The lowest percentages was found in Cheju Do, trol, sufficient to produce a bleb with an area of where 3 % of males and 1 % of females were positive approximately 20 mm2. The area of the ensuing reactors. Positive reactions were found in children wheals was estimated after 15 minutes by means of a in a highly endemic area as early as two years of transparent sheet on which calibrated rings out- age. Prior stool examinations in the same locality lining areas between 20 mm2 to 700 mm2 had been confirm this, with C. sinensis infections found in traced. In cases where the edges of the wheal were children as young as 18 months.1 With the exception somewhat indistinct, they were carefully outlined of the atypical 0-5-year age-group, males had a by drawing on the skin with a ballpoint pen to consistently higher rate than females (Table 3). In ensure greater ease and accuracy in estimating the general, an increase in the percentages positive size when viewing through the transparent film. occurred vith age up to 41-50 years. Under the testing procedure, three stations were set up for all persons being processed. At the first station essential information-i.e., name, age, sex, TABLE 2 and pertinent history-was entered on a serially PERCENTAGE OF POSITIVE REACTIONS numbered register. At this time, the corresponding TO SKIN TEST ANTIGENS BY PROVINCE register number was written with a ballpoint pen Clonorchis Paragonimus on the wrist of the person to be tested and the Province forearm swabbed with an alcohol sponge. At the Male Female Total Male Female Total second station, a few feet distant, the three intra- dermal injections were administered. For the first Kyonggi Do 22 6 15 4 1 3 person in each separate group, the time of injection Kang Wan 8 was also noted under the register number on the Do 3 6 5 2 4 Chung Chong Puk wrist. At the third station, the wheals were measured To 25 3 16 6 2 4 and recorded according to register number. The Chung Chong Nam information on the registry sheet and the results Do 41 12 28 6 2 5 were subsequently combined. Kyong Sang Puk To 53 14 36 6 2 4 Kyong Sang Nam RESULTS Do 38 25 33 11 8 9 Criteria for interpreting skin test reactions are Cholla Puk To 40 18 31 7 2 5 those reported in the studies mentioned previously. Cholla Nam Do 26 6 18 19 10 16 As indicated, even with purified antigens, limited Cheju Do 3 1 2 53 39 47 cross-reactions between clonorchiasis and para- gonimiasis are recognized. Since the size of the wheals resulting from the homologous antigen was Paragonimiasis found to be larger than those from the heterologous antigen, those individuals who reacted to both Positive reactors were found in all provinces antigens are regarded as being infected with the (Table 2 and Fig. 3). The most highly endemic parasite whose antigen elicited the largest wheal area was Cheju Do, with an over-all rate of 47 % (see the three articles by Sadun and co-workers). positive for all individuals tested, and the lowest It is recognized that with these criteria some infec- 1 I1 Chyu-unpublished data, 1958 724 B. C. WALTON & I. CHYU

FIG. 2 FIG. 3 PREVALENCE OF CLONORCHIASIS IN REPUBLIC PREVALENCE OF PARAGONIMIASIS IN REPUBLIC OF KOREA OF KOREA

TABLE 3 POSITIVE SKIN TEST REACTIONS TO CLONORCHIS ANTIGEN ACCORDING TO AGE AND SEX

Number examined Number positive I Percentage positive Age-group (years) Male Female Total Male Female Total Male Female Total

0-5 10 8 18 2 10 13 11 6-10 529 458 987 82 57 139 16 12 14 11-15 1 722 1 387 3 109 261 142 403 15 10 13 16-20 1 208 637 1 845 204 71 275 17 11 15 21-30 830 525 1 355 279 34 313 34 6 23 31-40 1 056 339 1 395 540 46 586 51 14 42 41-50 386 206 592 206 37 243 53 18 41 51+ 241 229 470 87 18 105 36 8 22

Total 5982 3789 9 771 1 660 406 2 066 28 11 21 CLONORCHIASIS AND PARAGONIMIASIS IN KOREA 725

TABLE 4 POSITIVE SKIN TEST REACTIONS TO PARAGONIMUS ANTIGEN ACCORDING TO AGE AND SEX

Number examined Number positive Percentage positive Age-group (years) Male Female Total Male Female Total Male Female Total

0-5 10 8 18 0 0 0 6-10 529 458 987 17 8 25 3 2 3 11-15 1 722 1 387 3 109 307 186 493 18 13 16 16-20 1 208 637 1 845 187 60 247 15 9 13 21-30 830 525 1 355 127 26 153 15 5 11 3140 1 056 339 1 395 111 32 143 11 9 10 41-50 386 206 592 57 21 78 15 10 13 50+ 241 229 470 65 25 90 27 11 19

Total 5 982 3789 9771 871 358 1 229 15 9 13

was Kyonggi Do, with 30%. As in clonorchiasis, is another factor contributing to the wide spread this is again predominantly an infection of males. of the disease. The rate for males was higher than for females in As is to be expected, the percentage of persons all provinces (Table 2) and all age-groups (Table 4). found positive by skin testing is higher than the rate obtained by single stool examinations. Likewise, DISCUSSION an estimate of the total number of cases of clonor- chiasis in the Republic of Korea, based on the over- One of the most striking findings of the present all prevalence rate of over 200%, gives a figure of survey was the widespread distribution of infections 4.5 million cases, which is several times the number with C. sinensis and P. westermani among adults. of most previous estimates (Stoll, 1947). This is in conflict with the usually accepted view that these infections occur primarily within limited The higher percentage of clonorchiasis among endemic foci. This universality of distribution is males is probably related to some social customs. especially true of clonorchiasis. Areas of low Social gatherings for drinking sul, a rice wine, endemicity are so widely scattered that this infection traditionally feature raw fish, when it is available, could be considered holoendemic in South Korea. as an accompaniment to the wine. Since women The cases are apparently more widespread than infrequently participate in such gatherings, they are the areas of high endemicity, where the infections have much less exposure to infection. are acquired. The majority of the cases occurring As was true with clonorchiasis, the movement of in many areas are probably not autochthonous. the population during the 1950-53 conflict probably Evidence of this was encountered in Chonan, where contributed to the widespread distribution of cases only a very few middle and high school students of P. westermani infection. It was found that some who were native to the area gave positive reactions. of the positive reactors in areas of low prevalence In contrast, the percentage of the adult population were refugees from known endemic areas in North showing positive reactions was almost five times as Korea or had travelled in highly endemic areas in high. Upon questioning, almost all the positive South Korea. reactors in the adult group admitted having travelled, Since the high infection rate on the island of or lived, in endemic areas and remembered eating Cheju Do is not considered typical of the whole raw fish there. The large-scale exodus of the majority country, this province was treated separately in of the population southward to the Pusan area in estimating the number of cases. An estimate based the Naktong valley during the Korean war probably on these data places the number of people infected

5 726 B. C. WALTON & 1. CHYU with P. westermani in the Republic of Korea at salting, and it is somewhat unlikely that the metacer- between 1 million and 1.5 million, with 125 000 cariae could survive the minimum of three days' cases on Cheju Do alone. Because the infection aging in the brine which the people deem necessary produces relatively serious pathological changes, for proper flavour. Possibly the previously accepted even with minimal numbers of worms, paragoni- explanation of the mode of infection should be miasis might appear to constitute a greater problem reconsidered and alternative infection routes con- than does clonorchiasis, in spite of affecting fewer sidered. Such an alternative method is suggested persons. by reports of the traditional home treatment for Ingestion of raw freshwater crab as food, long nr.easles practised in many areas. In a recent measles considered the primary source of Paragonimus epidemic in the Taegu area, it was determined that infection, is staunchly denied by many infected over 80% of the children affected were treated by persons. In many areas the usual method of pre- administering the liquor of crushed raw crayfish paration of the uncooked crab includes heavy (S. K. Lee-personal communication, 1958).

ACKNOWLEDGEMENTS The authors wish to thank Dr Chang Whan Sohn, of prefectural, gun, and local officials is gratefully Minister of Health and Social Affairs, for assistance acknowledged. Thanks are also due to Dr E. H. Sadun, which made the survey possible. The invaluable help Dr A. A. Buck and colleagues for permission to use the and co-operation of staff members of the Ministry and data from their prior skin test study reported herein.

RtSUMt II y a peu de temps encore, la frequence de l'infection douve pulmonaire. C'est dire que ces maladies sont de par la douve hepatique Clonorchis siniensis et la douve graves problemes de sante publique, particulierement la pulmonaire Paragonimus westermani, ne pouvait etre distomatose pulmonaire qui provoque de graves lesions, evaluee que d'apres les resultats de I'analyse des feces Les foyers de forte endemicite ne sont pas repandus dans ou des crachats, methode trop couiteuse et trop longue tout le pays. L'enquete a reve16 que les sujets malades pour etre appliquee de fagon systematique dans des se sont infectes dans les zones endemiques. Durant ces enquetes. dernieres annees, les migrations et la guerre ont elargi Un test intradermique, simple et suir, a ete recemment la repartition de ces distomatoses. La consommation mis au point, fond6 sur 1'emploi d'antigenes purifies de poissons ou de crabes d'eau douce crus, h6tes des (fractions proteiniques des trematodes) provoquant une metacercaires, a ete consid6ree longtemps comme la reaction cutanee en forme de cloque chez les sujets principale source d'infection. I1 est toutefois probable infestes. qu'elle n'est pas la seule. Le traitement des enfants Pres de 10 000 habitants de la Republique de Cor6e atteints de rougeole par le liquide provenant d'ecre- ont et soumis a ce test, qui a revele une frequence de la visses crues ecrasees pourrait etre a l'origine de certaines maladie beaucoup plus elevee qu'on ne le pensait, et de ces infections. La frequence plus elevee chez les une repartition beaucoup plus vaste. Dans la seule hommes peut s'expliquer en partie par le fait que ceux-ci, Coree du Sud, on estime que 4,5 millions de personnes dans leurs reunions dont les femmes sont exclues, accom- sont parasitees par la douve du foie, et 1,5 million par la pagnent de poisson cru les libations d'alcool de riz.

REFERENCES Crane, P. S., Bush, 0. B. & Won, P. C. (1955) Trans. roy. Sadun, E. H., Buck, A. A. & Walton, B. C. (1959) Milit. Soc. trop. Med. Hyg., 49, 68 Med., 124, 187 Sadun, E. H., Buck, A. A., Lee, B. K., Moon, Sadun, E. H., Walton, B. C., Buck, A. A. & Lee, B. K. H. M. & Burke, J. C. (1959) Amer. J. Hyg., (1959) J. Parasit., 45, 129 69, 68 Stoll, N. R. (1947) J. Parasit., 33, 1