Two rare cases of Diphyllobothrium latum parvum type infection in Korea

Two rare cases of human infection with parvum (dwarf) type of Diphyllobothrium latum [syn. D parvum (Stephens,1908)], were discovered in Korea. The first case was a 46-year old houseife, from whom a kind of pseudophyllidean tapeworm eggs was detected in the feces. She was treated with praziquantel and purged, and a complete strobila with scolex, 120 cm in total length, was recovered. She recalled that she had eaten raw trouts at a raw-fish restaurant near the Chungju Lake. Another patient was a 22-year old medical student (male), who used to eat raw sea-foods. He discovered a chain of tapeworm proglottids, 15 cm in length, discharged spontaneously in his stool and brought it for identification. The worms from the two cases were compatible with D. parvum (Stephens, 1908) of which the taxonomic significance has long been questioned. After a detailed morphological study and review of literature, we designated the worms as D. latum parvum type. This is the first report on the occurrence of this rare type of D. latum infection in Korea.

Epidemiological studies on Metagonimus infection along the Hongcheon river, Kangwon province

The Hongcheon river system flows down through the Hongcheon area of Kangwon-do, and reaches to the Cheongpyeong Dam in Kyonggi-do. Stool specimens from the inhabitants residing along the Hongcheon river basin were examined to detect infection rate of Metagonimus sp., and the intermediate hosts were collected to detect larval stages. The results obtained were as follows: Thirty-nine (33 males and 6 females) out of 529 (314 males and 215 females) inhabitants were infected with Metagonimus sp., showing a total positive rate of 7.4 per cent. In eight areas surveyed, the specimens from Kulji-ri of Bukbang-myon at the middle part of the river showed the highest positive rate of 26.9 per cent (14 positives out of 52) (males; 38.2per cent). The specimens from Mogog-ri of Seo-myon at the downstream of the river showed a positive rate of 10.4 per cent (13 positives out of 125) (males;12.6 per cent). The positive rates in other regions were less than 10 per cent. The density of the first intermediate host, Semisulcospira sp., was the highest in Kulji-ri of Bukbang-myon (10-20 snails per m(2)), and the infection rate of Metagonimus cercariae in the snails was 10.7 per cent(13 positives out of 121 snails). The infection rate of Metagonimus metacercariae in Zacco platypus, the fresh water fish favorably eaten raw by the inhabitants, was 68.2 per cent (30 positives out of 44 fishes), and most metacercariae were detected under the scales (89.9 per cent). Adult flukes were obtained from the small intestine of a rat, 15 days after infection with the metacercariae obtained from Z. platypus. These adult flukes were identified to be the same srecies as those obtained from human hosts. By this survey, new endemic areas of Metagonimus infection were discovered along the Hongcheon river basin and the main source of infection was the fresh water fish, Z. platypus.

Epidemiological survey on Metagonimus yokogawai infection in the eastern coast area of Kangwon-province, Korea

An epidemiological survey on Metagonimus yokogawai infection was performed in the eastern coast area of Kangwon province. Formalin-ether concentration technique and Stoll's dilution egg counting method were employed to figure out the prevalence and intensity of M. yokogawai infection and eating habits of inhabitants with raw freshwater fish. The results are summarized as follows: The prevalence rate of M. yokogawai infection was 6.6% among a total of 2,357 examinees; 8.6% (115 out of 1,345) in male and 4.0% (40 out of 1,012) in female. The prevalence rates were different by the streams where the examinees were residing: 17.8% along the area of Ohsip-cheon (stream), 11.8% along Maeup-cheon, 1.7% along Hwasang-cheon, 1.3% along Yeongok-cheon, 0.9% along Namdae-cheon, 0.9% along Sa-cheon and 0% in the other streams (Yongchon-cheon, Kangnung Namdae-cheon and Jusoo-cheon) in decreasing order. By social strata, the positive rate was 8.0% (122 out of 1,521) in general inhabitants and 3.9% (33 out of 836) in school children. By the intensity of infection by means of EPG counts in feces; the light infection (less than 400/EPG) was 74.1%, moderate infection (401-1,000/EPG) 17.3% and heavy infection (more than 1,001/EPG) 8.6%. Twelves out of 50 sweetfish (Plecoglossus altivelis) (24%) caught from the streams in eastern coast of Kangwon-Do were infected with metacercariae of M. yokogawai, and the number of larvae detected were 70.7 per fish in average. The metacercarial infection rate in fish were also different by the streams; 100% in Ohsip-cheon of Samcheok-Gun, 14.3% in Sa-cheon, 16.7% in Yeongok-cheon of Myeongju-Gun and 0% in Namdae-cheon of Yangyang-Gun, respectively. Six hundred ninety five (695) out of 1,396 inhabitants and school children (49.8%) were experienced in eating raw freshwater fishes (Plecoglossus altivelis, Tribolodon hakonensis, Coreoperca sp., Moroco sp., Carassius sp. & Cyprinus sp. and Zacco platypus). The data were assayed with the questionnaire collected from the examinees. In summarizing the above results, it is known that the Ohsip-cheon area of Samcheok-Gun is highly infected region, and the other areas of Kangnung Namdae-cheon, Yeongok-cheon and Yangyang Namdae-cheon are very lowly infected or non-infected regions for M. yokogawai infection.

Experimental and epidemiological studies on the life cycle of Echinostoma hortense Asada, 1926 (Trematoda:Echinostomatidae)

Recently there have been some reports on human infections of Echinostoma hortense in Korea. It was found that a few species of freshwater fishes were playing the role of the second intermediate host of E. hortense. However, molluscan intermediate host has not been identified yet in Korea. The present study aimed to establish the life cycle of E. hortense in laboratory. Experimental studies such as egg production from the rat, development of the eggs in vitro, exposure of miracidia to freshwater snails, shedding pattern of cercariae from infected snails, morphology of cercariae, cercarial infection to the second intermediate host and infection of metacercariae to the difinitive hosts were done. In addition, epidemiological surveys on the infection status in inhabitants and house rats, and on the natural infection of larval echinostomes in the snails and fishes were carried out along the South Hangang-river. The results obtained were as follows: The eggs deposited from adults in physiological saline were cultivated at room temperature (20-24C). The miracidia were firstly observed on 8 days after cultivation, and 85.5 per cent of the eggs contained the mature miracidia on 11 days after cultivation. More than 90 per cent formed the miracidia when cultivated at temperature 22-27C. Hatching of the miracidia began on 12 days after cultivation and continued for a week. The size of the miracidia was 103.0 x 51.4 micrometer in average. The motility of miracidia were active up to 8 hours after shedding, but they were all dead within 10 hours after shedding. A freshwater snail, Radix auricularia coreana was cultivated in aquaria. A hatched F1 snails from the egg masses were exposed to 20 miracidia respectively. Escape of cercariae started on 15 days after infection. Radix auricularia coreana was experimentally identified as the first intermediate host of E. hortense in Korea. Cercarial shedding started on 15-20 days after infection by snail, continued for about 10 days (8.8 days in average). Infected snails were dead within 32 days after the miracidial infection. About 1,335 cercariae (328-1,994) per snail were shed in its life, and 119 cercariae in average per snail per day were shed. The cercariae were motile for more than 24 hours, and then squirming at the bottom until death. The body and tail sizes of cercariae were 356 x 186 micrometer and 510 x 68 micrometer in average, respectively. The rediae parasitized in the snail hosts were found mainly around the pericardial regions, and their size was 1,575 x 258 micrometer in average. The numbers of developing cercariae in a mature redia were 14 in average (7-20 in range). The numbers of rediae in a snail were 102 in average on 15 days after miracidial infection and 221 in average on 28 days. Three uninfected Misgurnus anguillicaudatus, less than 6.5 cm long were used in for the cercaria1 infection. They were all exposed with 755 cercariae, and examined at 5-day intervals starting from 10 days after infection. All the fihes were infected with metacercariae of E. hortense and a total of 275 was found infected (36.4 per cent). The metacercariae were fed to rats and the adult worms were obtained on 15 days after infection. The infected rats began to deposit the eggs on 11 days after infection. The number of eggs deposited per day per worm (EPD/worm) was 400-500 on 3 weeks after infection and was increased to 1,000-1,500 on 4 to 17 weeks, then decreased to 800 on 2l weeks after infection. A total of 745 stool specimens collected from 576 male and 169 female residents of 8 different villages along South Hangang basin was examined. Out of 745 specimens, the eggs of Echinostoma sp. were found in 2 cases (0.3 per cent). Of 34 house rats one showed egg-positive (2.9 per cent). Total 971 Radix auricularia coreana collected from 7 sampling stations were examined for shedding of cercariae. Three snails (0.3 per cent) shed the cercariae of E. hortense. A total of 119 out of 542 freshwater fishes (22.0 per cent) had the metacercariae of E. hortense. The fishes parasitized with the metacercariae were 4 out of 14 examined species. The infection rate of 4 species were 34.1 per cent (106 out of 311) in Misgurnus anguillicaudatus, 30.4 per cent 7 out of 23) in Misgurnus mizolepis, 4.3 per cent (2 out of 46) in Moroco oxycephalus and 22.2 per cent (4 out of 18) in Odontobutis obscura interrupta. In summarizing the above results, the first intermediate host of E. hortense was found as Radix auricularia coreana in Korea. Also it took about 46 days for the shortest completion of a life cycle of E. hortense in summer; that is, 10 days for miracidial development in eggs, 15 days for cercarial development in the snail, about 10 days for metacercarial development in the second intermediate hosts, 11 days for the maturation as the adults in the definitive hosts. The natural infection rates of E. hortense in the intermediate hosts were relatively high but those in the definitive hosts were low in the middle areas of South Hangang basin.

Two cases of human infection by Echinostoma cinetorchis

Eggs of Echinostoma sp. were found from two patients who were hospitalized between Oct. and Dec. 1985. Single dose of 10 mg/kg of praziquantel was prescribed to each patient and after purgation with magnesium salt seven and two adult worms of Echinostoma cinetorchis in respect were recovered from patients. The first case was a 54-year-old male residing at Chungju city in Chungbuk province. He was hospitalized because of severe weight loss and frequent urination. The second case was a 71-year-old male residing at Chungsun-kun in Kangwon province, and hospitalized due to suspected lung cancer. The average size of the eggs found in the stools was 98 x 63 micrometer (the first case) and 100 x 67 micrometer (the second case) respectively, and total nine worms collected were identified as E. cinetorchis.

Echinostoma hortense metacercariae naturally encysted in Odontobutis obscura interrupta (a freshwater fish) and experimental infection to rats

The metacercariae of an echinostomatid fluke were detected from a freshwater fish, Odontobutis obscura interrupta caught from the Seom river system, Wonseong-gun, Kangwon-do, and experimenally infected into rats to obtain the adult worms for the species identification. A total of 32 metacercariae was detected from 10 fishes (27.8 percent) out of 36 O. obscura interrupta caught from the river. The average size of metacercariae was 153.4 x 149.0 micrometer. Also, it was uniquely specific that thickened membrane was formed around the metacercarial cyst wall. The rats orally infected with those metacercariae were sacrificed 20 days after infection to get the adult worms. The mean length and width of the adult worms were 0.75 cm and 0.13 cm, respectively. The number of collar spines on circumoral disk was 26 to 28, and the end group spines at lateral sides of the oral sucker were 4 on each side. The echinostomatid flukes observed in this study were all identified as Echinostoma hortense according to the morphologies of the cirrus sac, ovary, vitellaria and testes of the adult worms and the shape of eggs. On the other hand, O. obscura interrupta is one of the fresh-water fish that are preferably eaten raw by the rural inhabitants. Although no human case of E. hortense infection by eating O. obscura interrupta has been experienced yet, the possibility is strongly suggested in this study.

Rhabditis sp. infected cases in rural school children

Five cases infected with Rhabditis sp. were detected in a survey to examine the stool specimen from rural primary school children. A large number of the larvae of Rhabditis sp. detected by the direct cellophane thick smear were cultured by the filter paper method. The examination was carried out in April through June 1980 in Tangjeong-Myon, Ahsan-Gun, and in September 1983 in Sandong-Eup, Yeongwol-Gun. The results obtained in this study were as follows: Prevalence: Out of 925 children, 5(0.54 percent) children were found to be positive. The number of the detected larvae was 110/0.1 gm of feces in case 1, 35 in case 2, 130 in case 3, 86 in case 4 and 62 in case 5. Larvae: The larvae were prepared by means of the direct fecal smear and measured by a micrometer equipped in the microscope. Twelve(12) through 15-day old larvae in culture were 197.1 micrometer long in average, and the maximum size of the matured stage larvae was 884.0 x 25.9 micrometer. However, the length variation was ranged as 173.0 to 884.0 micrometer. Adults: The size of clubbed adult female was 1,357 micrometer(1,176-1,419) in length and 80 micrometer(79-82) in width. Length of buccal cavity was 33 micrometer. A long cylindrical esophagus (273 micrometer) of the worms with a valved posterior cardiac bulb and with median bulbar swelling was morphologically indicated. Distance from mouth to vulva was occupied 58 percent of body length. Male worm was 1,006 micrometer (890-1,148) in length and 49 micrometer(48-49) wide. Caudal alae of bursa and spicules (75 micrometer in length) were well developed. Eggs: The oval shaped eggs in the female uterus, when cultured, were 66 x 56 micrometer in size, and the eggs laid by the adult could not be detected. So, reproduction might be through to be ovoviviparity. The five cases were re-examined during the period from the 1st to the 3rd week after stool examinations, but Rhabditis sp. were detected again in 4 cases in 1st week. When they were examined in 3rd week, larvae could not be detected . So, it was thought that the infection of Rhabditis sp. to humans was facultative.

Two cases of natural human infection by Echinostoma hortense and its second intermediate host in Wonju area

Two cases of human Echinostoma hortense infection and their probable infection source were identified by praziqantel (Distocide) treatment of the patients and by examining two kinds of fresh water fish which were eaten raw by them. The result of the research can be summarized as follows: The patients, each aged 31 and 30, were residing in the same house in Wonju City, Kangwon Province. The first case was hospitalized due to epidemic hemorrhagic fever (E.H. fever) and the second case was healthy but had slight degree of abdominal pain and diarrhea from time to time. In the stool examination, eggs of E. hortense (114.3 x 71.0 micrometer average from the first case and 119.1 x 68.3 micrometer average from the second) were found. By administering single dose of praziquantel (10~15 mg/kg) and purgation with magnesium salt to them, six adults of E. hortense were collected from the diarrheal stools of the second case. By examining 84 Moroco oxycephalus and 20 Carassius carassius which were captured at the place where the two patients had captured and eaten the fresh water fish, the metacercariae of Echinostoma sp. were found from 3 (3.5 percent) M. oxycephalus. After the experimental infection of 3 isolated metacercariae to one albino rat three adults of E. hortense were recovered. By the present study, the two patients revealing the echinostomatid eggs in their stools were proven to be infected with E. hortense and to be the second and third human cases of this fluke infection in Korea. Moroco oxycephalus harboured the metacercariae of E. hortense and appeared to be a new second intermediate host.

Epidemiological studies on Metagonimus yokogawai infection in Samcheok-gun, Kangwon-do, Korea

An epidemiological study on Metagonimus yokogawai infection was performed in Samcheok-gun, Kangwon province during the period from November 1983 to October 1984. Formalin-ether concentration technique and Stoll's dilution egg counting method were employed to figure out the prevalence and infection intensity of M. yokogawai infection. The results are summarized as follows: The prevalence of M. yokogawai infection was 13.3 percent among 1,172 examined ; 18.0 percent (114 out of 632) in male and 7.8 percent (42 out of 540) in female. The prevalence rates were different by stream; 15.5 percent in Ohsip-chon (stream), 11.8 percent in Maeup-chon and 1.6 percent in Gagok-chon. Along the basin of Oship-chon; 8.2 percent at the lower reaches in Samcheok-eup, 25.9 percent at the middle reaches in Miro-myon and 6.2 percent at the upper reaches in Dogeoe-eup, respectively. By age group, the highest rate (18.3-20.2 percent) was observed in 30-49 years of age (male : 24.1-28.7 percent, female 11.2-13.2 percent). By social strata, the positive rate was 15.0 percent (120 out of 799) in general inhabitants and 9.7 percent (36 out of 373) in school children. Intensity by EPG count in feces was 419 in average; the light infection (less than 400 EPG) was 70.4 percent, moderate infection (401-1,000 EPG) 19.4 percent and heavy infection (more than 1,001 EPG) 10.2 percent respectively. All the 67 sweetfish (length 10.3-18.5 cm) which were caught from Ohsip-stream were infected with metacercariae of M. yokogawai and the number of metacercariae detected were 382 per fish in average (323 in June and 382 in September). Experiences of intake of raw fresh-water fish [Plecoglossus altivelis and Leuciscus (Tribolodon) sp.] were present in 50.3 percent (354 out of 704) of the inhabitants along Ohsip-stream according to questionnaire study. The results of this survey indicated that the middle reaches of Ohsip-stream in Miro-myon, Samcheok-gun is the endemic region for M. yokogawai infection.

A Case of Human Fascioliasis

No abstract available.

Epidemiological studies on Clonorchis sinensis infection along the Nam-river in Gyeongnam province, Korea

The prevalence of C. sinensis infection along the Nam river, Korea, was 38.7% of 5,291 people examined. Prevalence rates varied from 42% at the upper stream to 34% at the middle stream and 40% at the down stream region. Rates were highest (53.4-54.3%) in the 30-59 years of age group. The positive rates in primary school chidren, school students, teachers and local officers, and other inhabitants were 16.5%, 22.6%, 46.2% and 49.6% respectively. 53.6% of cases were light infected, i.e. less than 4,000/EPG. The cercarial expulsion rate of 5,005 Parafossarulus sp. was 0.34%. Snails naturally infected with C. sinensis expelled about 788 cercariae/day. Ten of 18 species of freshwater fish examined had C. sinensis metacercariae. To prevent clonorchiasis in the endemic areas, the effective health education system is suggested as a control measure. [retyped from English summary]

Epidemiological study on Metagonimus yokogawai infection along Boseong River in Jeonra Nam Do, Korea

Prevalence study of Metagonimus yokogawai infection, survey of intermediate hosts of Metagonimus yokogawai and food habits of raw sweetfish among inhabitants along Boseong river (120 km), Jeonra Nam Do (province) were carried out. The results are summarized as follows: Among 360 examined, the egg positive case were 128(35.6 percent); male 112(46.7 percent), female 16(13.3 percent). The prevalence rates were different by geographical areas; 42.4 percent in down stream, 49.4 percent in middle stream and 13.3 percent in upper stream. By ages, highest rate, 53.6-59.1 percent was observed among 30-49 group (male 69.6-73.0 percent, female 15.8-35.5 percent). Eggs per gram of feces were 2,084 (200-12,280) in average; down stream 1,708, middle stream 2,590, upper stream l,550. By social strata, the prevalence showed differences; 24.8 percent in primary schoolchildren, 78.4 percent in school teacher and local officers, 30.6 percent in general inhabitants. Clonorchis sinensis infected cases in the areas were 21(5.8 percent) out of 360 examined, and 90.5 percent of them showed mixed infection with Metagonimus yokogawai. Cercariae of Metagonimus yokogawai from the lst intermediate host, Semisulcospira sp., in down and middle streams were detected from 32 snails (5.9 percent) out of 545 examined. All the 22 Plecoglossus altivelis which were caught from the down stream were infected with metacercariae of Metagonimus yokogawai. The number of the metacercariae detected was 22,650 per fish in average, and the number increased from August to October. Experiences of raw sweetfish intake of the inhabitants were found in 208(58.4%) among 356 interviewed by questionaire form (male 76.7 percent, female 20.7 percent). Means of acquisition of the sweetfish were mostly by purchase 68.8 percent, and seasonally in summer. Reason of the raw sweetfish intake was due to the flavor, 83.2 percent. The fish were mixed in soy sause with vinegar before the intake.

Niclosamide in the treatment of tetagonimiasis

Anthelmintic effect of niclosamide [N-(2-chloro-4-nitrophenyl)-5-chloro-salicylamide)] on Metagonimus infection was carried out to the cases in area of Seomjin-river. The drug, one tablet contains 0.5 g of niclosamide was supplied from Bu-gwang pharmaceutical company in Seoul. Sixty five cases were divided into three groups by the regimen: Group l given 2 g(4 tablets) for one day, Group II for two successive days and Group III for three successive days. Stool examination was done before and 2-3 weeks after the drug administration by formalin-ether concentration and Stoll's dilution egg counting techniques. The results were as follows: Egg negative conversion (cured) and egg reduction (more than 80 percent decrease) rates were 28.6 percent, 10.7 percent in group I, and 31.8 percent, 27.3 percent in group II. But of those in group III treated for three successive days, 73.3 percent was cured and 26.7 percent showed egg reduction, and the general egg reduction rate was 95.1 percent. The results in the present trial suggested that the niclosamide has anthelmintic efficacy when it is used in 2 g for more than three successive days.

Fates of degranulated mast cells and extruded granules responded to homologous antigen in rats infected with Clonorchis sinensis

: Fates of degranulated mast cells by challenge of the homologous antigen to the Clonorchis sinensis infected rats, and the extruded granules were examined by means of light and electron microscopy. The whole experiment was carried out six weeks after the Clonorchis infection and an observation was made at 1, 3, 5, 8, 12 hours after the antigen challenges. The abdomen of the infected rat was cut open by 2 centimeters and the antigen was directly inoculated to mesentery, then again sutured. According to the scheduled period, the rat was sacrificed. The challenged portion was cut out and followed by dying procedure. The results of the observation are summarized as follows: Degranulation was observed within one hour without noticeable change of the granules. Three hours after the inoculation, the shed granules were phagocytized by macrophage surrounding the mast cells. They were aggregated in the cytoplasm. In 5 days phagocytosis phenomenon were almost completed but still some granules were scattered in surroundings upto 12 hours. The nucleus of the degranulated cell appeared clearly in contrast to normal cells which were killed with granules. Membrane became to normal, and the granules which were not expelled out agglomerated in a large cavity. The above resulst suggest that the partially degranulated mast cells do not disintegrate, but recover to normal, and expelled granules are phagocytized by macrophages.

Flea fauna of rodents in coastal region of Korea :Insecticide susceptibility test of Xenopsylla cheopis

A survey on rats and rat-fleas was performed in costal area of Korea during 1972 in Inchon, Kunsan, Yosu, Busan and other areas. The number of the caught rats was 1,448. Total number of collected fleas was 2,480. Geographical distribution were described. Flea index was in 1.71 total. Mothly flea indices were 0.35-0.84 in January to March, 2.13-2.59 in April to June, 0.58 in July and 1.82-4.91 in August to November. Mortality rate of X. cheopsis to various concentration of DDT in 1 hour exposure were 43.8 % in 4.0 %, 30.4 % in 1.0 %. In 24 hours exposure, the mortalities were 100 % in 4.0 %, 91.5 % in 2.0 %, 73.5 % in 1.0 % and 37.0 % in 0.5 % DDT.

Experimental studies of 1, 4-Bis-trichlormethyl-benzol on the infection of Clonorchis sinensis(I)

The efficacy and toxicity of 1, 4-Bis-trichlor-methyl-benzol were examined in the animal infections(rat, rabbit and mouse) of Clonorchis sinensis. The effective dosages to kill the worm in bile ducts were 1 x 150 mg/kg in rat and 5 x 150 mg/kg in rabbit. During 48 to 72 hours after the administration of the drug, the inactive posteriorly swollen worms and variously degenerated worms were observed from liver ducts, gallbladder and intestine of the experimental animals. In gall bladder of rabbits, a plenty of fragments of the worms and clewed mass of eggs were confirmed under microscope. The E.P.G. was not decreased to zero in 3 weeks observation after the administraiton of the drug except rabbit No. 9 which was treated with the dose of 5 x 250 mg/kg. Minimal congestion and mild cloudy swelling of liver were observed in the groups of mice which were given 5 x 150 kg and 3 x 500mg/kg of the drug respectively. The body weight of experimental animals showed no evidence of changes.

Environmental Studies on Paragonimiasis in Korea

Environmental studies regarding Paragonimiasis have been done in Sulak-Myun, Kapyung-Goon (I district) and Yongmoon-Myun, Yangpyung-Goon (II district), both of which are considered "active" endemic areas, and in Byukje-Myun, Koyang-Goon (III district) an "arrested" area. 1. Paragonimiasis is still active in the Uhmos River, Sulak-Myun, Kapyung-Goon, where 49% of crayfish contained Paragonimus metacecaria. Snails which are the first intermediate host of Paragonimus westermani were moderately present. In the Oonke River, Yongmoon-Myun, Yangpyung-Goon, crayfish which are the second intermediate host of Paragonimus westermani, were found in every area of the river, but snails were not found in any area of either branch of the river. They were caught in areas which are located below the junction. In the Daeja river, Bykje-Myun, Koyang-Goon, crayfish were found only in the upper stream of the river and snails were not caught in any area of the river. 2. The results described above are attributed to the fact that snails, which have minimal mobility and vitality, were complete1y obliterated by the long, unprecedented drought in 1965. In contrust, crayfish with great mobility and vitality survived. Thus without the snail, the life cycle of Paragonimus western1ani become incomplete, and the clinical disease disappeared. 3. Rainfall is very important in maintaining water flow in the river, a necessary factor for the life cycle of Paragonimus westermani. Therefore we have charted tile amount of rainfall in the Seoul and Choonchun areas in 1965, compared with the average of the past 30 years, in order to ascertain the degree of drought which influnced the Paragonimus westermani hosts and cohabitants. 4. Geographic conditions which are also very important in maintaining water flow in small rivers was investigated. The conclusion was drawn, that a long river has an advantage over a short during drought; a tortuous river provides a better opportunity for miracidia of Paragonimus westermani eggs to migrate to snails, and for Pargonimus cercaria to invade crayfish than a straight rapidly flowing river. 5. We must conclude that man may ingest Paragonimus metacercaria by drinking water from shallow wells and streams in areas endemic to paragonimiasis, when we note that one crayfish of four caught in shallow wells in Kapyung-Goon contained many Paragonimus metacercaria. 6. Other factors are the increase in traffic due to the expanding population in Korean farm areas, and the increase in the use of farm chemicals, which seep into the rivers and reduce the number of snails, crayfish and crabs available as potential hosts. 7. In recent years, the wild fauna in the mountains, one of the important terminal hosts of Paragonimus westermani, have been markedly reduced in number. This may have contributed to decreasing paragonimiasis as directly infective to man. 8. Health education on paragonimiasis, informing the people of the dangers of eating raw or inadequately cooked crayfish and crabs, or those soaked less than 10 days in soysauce, and drinking the water from shallow wells and streams, is demonstrated to have decreased the incidence of this disease. 9. Because of the preceding facts, paragonimiasis in Kyunggi-Prvince is being decreased.

A new second intermediat host of genus Paragonimus

Metacercariae were found from 6 samples among 4,382 Parlemon nipponensis which were caught at Podu, Kohung, Korea. The metacercaria was inclined as a larval stage of Paragonimus westermani by following reason: Semisulcospira libertina was the only one species which lives in Podu area. No other metacercaria except Paragonimus westermani were found from the craw or cray fish which were caught in the endemic aera. Metacercariae, ovary, testes and cuticular spines resmbled the characteristics of Paragonimus westermani, which have been described by previous workers.