Infection Status of Estuarine Fish and Oysters with Intestinal Fluke Metacercariae in Muan-gun, Jeollanam-do, Korea

The source of human infection with intestinal flukes was surveyed in estuarine fishes, including the dotted gizzard shad, common sea bass, common blackish goby, redlip mullet, black sea bream, and oyster collected from Muan-gun, Jeollanam-do, Korea during August and September 2007. Collected fishes and oysters were artificially digested in pepsin-HCl solution and examined under a stereomicroscope. In 36 shads (Konosirus punctatus) and 20 basses (Lateolabrax japonicus) examined, Heterophyopsis continua metacercariae were found in 58.3% and 100%, and their average numbers were 12.0 and 6.3 per infected fish, respectively. In 34 gobies (Acanthogobius flavimanus) examined, metacercariae of H. continua were detected in 79.4%, Stictodora lari in 97.1%, and Acanthotrema felis in 92.1%, and their average numbers were 45.8, 189.3, and 235.3 per infected fish, respectively. In 37 redlip mullets (Chelon haematocheilus), Heterophyes nocens metacercariae were found in 56.8%, Pygidiopsis summa in 94.6%, and Stictodora fuscata in 45.9%, and the average metacercarial densities were 17.4, 31.3, and 35.1 per infected fish, respectively. In 30 black sea breams (Acanthopagrus schlegeli) and 45 oysters (Crassostrea gigas) examined, no metacercariae were detected. From the above results, it has been confirmed that the dotted gizzard shad, common sea bass, common blackish goby, and redlip mullet from Muan-gun, Jeollanam-do, Korea are infected with the metacercariae of heterophyid flukes.     

A new endemic focus of Heterophyes nocens and other heterophyid infections in a coastal area of Gangjin-gun, Jeollanam-do

To know the prevalence of heterophyid trematodes among inhabitants of a southern coastal village, i.e., Sacho-ri, Gangjin-gun, Jeollanam-do (Province), 82 stool samples were examined on helminth eggs and protozoan cysts using Kato-Katz and formalin-ether sedimentation techniques. Total 33 people (40.2%) were positive for trematodes (Heterophyes nocens 15 people, Pygidiopsis summa 3, Metagonimus sp.; 4, Clonorchis sinensis 7, Gymnophalloides seoi 6) and/or protozoa (Entamoeba coli 3). Among intestinal trematode egg positive cases, 17 were treated with praziquantel and their whole diarrheic stools were collected after purgation. Adult flukes of H. nocens (number of specimens = 1,294), P. summa (386), Stellantchasmus falcatus (5), Stictodora lari (4), and Heterophyopsis continua (1) were collected using a stereomicroscope. To know the source of human H. nocens infections in this village, metacercarial infections in mullets (10) were examined and most H. nocens metacercariae (101/105, 96.2%) were found in the trunk portion. From above results, the surveyed coastal village has been newly known as an endemic focus of human H. nocens infection and consuming raw mullets was the presumable source of human heterophyid infections.     

Heterophyid metacercarial infections in brackish water fishes from Jinju-man (Bay), Kyongsangnam-do, Korea

Heterophyid metacercarial infections in brackish water fishes, i.e., perch, shad, mullet, redlip mullet, and goby, of Jinju-man (Bay), Kyongsangnam-do, Korea, were investigated using a digestion technique. Among 45 perch (Lateolabrax japonicus), the metacercariae of Heterophyopsis continua were found in 55.6% (18.5 metacercariae per fish), Stictodora spp. in 28.9% (3.6), and Metagonimus takahashii in 6.7% (17.0). The metacercariae of H. continua were detected in 23 (65.7%) of 35 shad (Konosirus punctatus). Among 15 mullet (Mugil cephalus), the metacercariae of Pygidiopsis summa were found in 100% (105.9 metacercariae per fish), Heterophyes nocens in 40.0% (8.5), H. continua in 13.3%, and Stictodora spp. in 6.7%. Among 12 redlip mullet (Chelon haematocheilus), the metacercariae of P. summa were detected in 91.7% (1,299 metacercariae per fish), H. nocens in 16.7%, and Stictodora spp. in 16.7%. Among 35 gobies (Acanthogobius flavimanus), the metacercariae of Stictodora spp. were found in 82.9% (44.5 metacercariae per fish), and H. continua in 25.7% (2.8). The adult flukes recovered from a cat experimentally infected with metacercariae from perches were compatible with M. takahashii. The results confirm that the estuarine fish in Jinju-man (Bay) are heavily infected with heterophyid metacercariae. Furthermore, it was found for the first time that the perch acts as a second intermediate host for M. takahashii.     

Echinostoma hortense and Heterophyid Metacercariae Encysted in Yellowfin Goby, Acanthogobius flavimanus, from Shinan-gun and Muan-gun (Jeollanam-do), Korea

Fishborne trematode (FBT) metacercariae were investigated in yellowfin goby, Acanthogobius flavimanus, collected from Shinan-gun and Muan-gun, Jeollanam-do (province), Korea. All collected fishes were examined using the artificial digestion method. In all of 15 gobies from Aphae-myeon in Shinan-gun, metacercariae of Stictodora spp. (334 metacercariae/fish), Heterophyes nocens (153/fish), and Heterophyopsis continua (20/fish) were detected. In 2 of 14 gobies from Jido-myeon in Shinan-gun, 8 Echinostoma hortense metacercariae in total were detected. In 15 gobies from Haeje-myeon in Muan-gun, the metacercariae of H. continua were found in 100%, Stictodora spp. in 86.7%, and H. nocens in 6.7% of fish examined. The average numbers of metacercariae per infected fish were 23.3 (H. continua), 416.0 (Stictodora spp.), and 2.0 (H. nocens), respectively. The metacercariae of E. hortense found in gobies were elliptical, with 150 × 138 µm in average size, and had 27 collar spines on the head crown. The above results suggest that yellowfin gobies from 2 localities may be the potential infection sources of FBT. Moreover, it is proved for the first time that the yellowfin goby, A. flavimanus, acts as a second intermediate host for E. hortense.     

Prevalence of Metagonimus metacercariae in sweetfish, Plecoglossus altivelis, from eastern and southern coastal areas in Korea

The present study was performed to determine the current infecion status of Metagonimus yokogawai metacercariae in sweetfish, Plecoglossus altivelis, collected from several streams in eastern and southern coastal areas of Korea. The sweetfish collected were artificially digested with pepsin-HCl solution and examined under a stereomicroscope in August and September, 2007. Out of 145 sweetfish collected from 10 streams in eastern coasts (Gangwon-do and Gye-ongsangbuk-do), 88 (60.7%) were infected with Metagonimus metacercariae. The average metacercarial density was 61 per infected fish. Among 141 sweetfish collected from 10 streams in southern coasts (Gyeongsangnam-do, Ulsan Metropolitan city, and Jeollanam-do), 140 (99.3%) were infected with Metagonimus metacercariae, and their average density was 949 per infected fish. The present study confirmed that M. yokogawai metacercariae are still prevalent in the sweetfish from several eastern and southern coastal localities. The prevalence and metacercarial density were much higher in the sweetfish from streams of southern coasts than in those of eastern coasts. Therefore, attention should be paid to this small fluke infection, and consumption of raw sweetfish naturally produced in these areas should be prohibited.     

Food-borne intestinal trematode infections in the Republic of Korea

A total of 19 species of food-borne intestinal trematodes have been reported in humans in the Republic of Korea. They include 12 species of the Heterophyidae, Metagonimus yokogawai, M. takahashii, M. miyatai, Heterophyes nocens, H. heterophyes (imported), H. dispar (imported), Heterophyopsis continua, Pygidiopsis summa, Stellantchasmus falcatus, Centrocestus armatus, Stictodora fuscata, and S. lari; four species of the Echinostomatidae, Echinostoma hortense, E. cinetorchis, Echinochasmus japonicus, and Acanthoparyphium tyosenense; and one species each of the Neodiplostomidae, Neodiplostomum seoulense, Plagiorchiidae, Plagiorchis muris, and Gymnophallidae, Gymnophalloides seoi. Fresh water fish harbor the metacercarial stage of M. yokogawai, M. takahashii, M. miyatai, C. armatus, E. hortense, E. cinetorchis, E. japonicus, or P. muris. Brackish water fish serve as the second intermediate hosts for H. nocens, H. continua, P. summa, S. falcatus, S. fuscata, and S. lari. Brackish water bivalves are the source of infection with A. tyosenense. Tadpoles and frogs are the second intermediate hosts for N. seoulense, but the major source of human infection is the grass snake Rhabdophis tigrina, a paratenic host. The metacercariae of G. seoi are observed in oysters. The natural definitive hosts are, in most cases, mammals such as rats, cats and dogs. However, several species (C. armatus, S. lari, E. japonicus, A. tyosenense, and G. seoi) have birds as natural definitive hosts. Host-parasite relationships, pathogenesis and pathology, immunity, clinical aspects, differential diagnosis, treatment, prevention and control of these intestinal trematodes are briefly discussed.     

Comparative morphology of minute intestinal fluke eggs that can occur in human stools in the republic of Korea

The egg morphology of minute intestinal flukes (MIF) that can occur as human infections in the Republic of Korea, i.e., Metagonimus yokogawai, M. miyatai, M. takahashii, Heterophyes nocens, Heterophyopsis continua, Stellantchasmus falcatus, Stictodora fuscata, Pygidiopsis summa, and Gymnophalloides seoi, was studied in comparison with Clonorchis sinensis. The adult worms were obtained from residents of endemic areas, and their intrauterine eggs were studied and measured using light microscopy; the length, width, length-width ratio (LWR), and Faust-Meleney index (FMI). Several specimens were processed for scanning electron microscopy (SEM), and before gold-coating, the uterine portion of each fluke was etched with a sharp pin in order to expose the eggs. The MIF eggs were ovoid, pyriform, or elliptical with a size range of 21-35×12-21 μm. S. fuscata eggs revealed the highest FMI (largest in the area) and lowest LWR, whereas P. summa eggs showed the lowest FMI and medium LWR. SEM revealed that G. seoi and S. fuscata had remarkably clean shell surface lacking the muskmelon-like structure which is prominent in C. sinensis eggs. In Metagonimus spp., H. continua, H. nocens, and S. falcatus eggs, minute surface ridges were recognizable though less prominent compared with C. sinensis. On the surface of P. summa eggs, thread-like curly structures were characteristically seen. The results revealed that important differential keys for MIF eggs include the length, width, area (FMI), shape of the eggs, and the extent of the muskmelon-like structure or ridges on their shell surface and operculum.     

A new endemic focus of Gymnophalloides seoi infection on Aphae Island, Shinan-gun, Jeollanam-do

A new endemic focus of Gymnophalloides seoi infection has been discovered on Aphae Island (Shinangun, Jeollanam-do), Republic of Korea. This area, which is referred to as Bokyong-ri, is a small seashore village located in the northern portion of the island. Fecal samples were collected from a total of 57 residents and examined by the Kato-Katz and formalin-ether sedimentation techniques. Helminth eggs were detected in 37 samples (64.9%); 33 samples were positive for G. seoi eggs (57.9%), 4 for Pygidiopsis summa (7.0%), 13 for other heterophyids (22.8%), 1 for Clonorchis sinensis (1.7%), and 1 for Trichuris trichiura (1.7%). Women (70.4%) revealed higher rates of G. seoi infection than did men (46.7%), and individuals older than 50 years of age also evidenced higher rates of G. seoi infection than in other age groups (P < 0.05). In worm collection from 13 G. seoi egg positive cases, G. seoi (total 86,558 specimens), Heterophyes nocens (278), Stictodora sp. (10), Heterophyopsis continua (3), P. summa (3), and unidentified flukes (42) were collected. Oysters, the source of G. seoi infection, were collected from an area proximal to the village and 50 were examined for metacercariae; 47 (94%) were found infected and the observed metacercarial density was 9.5 +/- 8.9 per oyster. The results of this study indicate that Bokyong-ri is a new endemic area of G. seoi infection, with high rates of infection in humans and oysters.     

Two species of goby, Boleophthalmus pectinirostris and Scartelaos sp., as the new second intermediate hosts of heterophyid fluke in Korea

A survey was performed in order to determine the infection status of the metacercariae of heterophyid fluke in two goby species, Boleophthalmus pectinirostris and Scartelaos sp., collected from Gangjin-gun, and Shinangun, Sooncheon-shi, Jeollanam-do, Republic of Korea. A total of three metacercariae of Heterophyopsis continua was found in only one B. pectinirostris (10.0%) from Gangjin-gun. Heterophyes nocens metacercariae were detected in 24 B. pectinirostris (96.0%) and 14 Scartelaos sp. (63.6%) from Shinan-gun. Heterophyopsis continua metacercariae were found in 11 B. pectinirostris (44.0%) and 21 Scartelaos sp. (95.5%) from Shinan-gun. Stictodora fuscata metacercariae were detected in 18 B. pectinirostris (72.0%) from Shinan-gun. No metacercariae were detected in 20 B. pectinirostris from Sooncheon-shi. From the above results, this study is the first to prove that B. pectinirostris and Scartelaos sp. serve as the second intermediate hosts of some heterophyid flukes in Korea.     

Identification of Stictodora lari (Heterophyidae) metacercariae encysted in the brackish water fish, Acanthogobius flavimanus

Metacercariae of the genus Stictodora encysted in the head tissue of Acanthogobius flavimanus (the gobies) caught at Sachun-gun, Kyongnam Province, were identified to be Stictodora lari Yamaguti, 1939 (Trematoda: Heterophyidae), a new parasite fauna in Korea. The metacercariae were 0.39-0.43 mm by 0.32-0.35 mm in size, long elliptical, and with a thin and transparent cyst wall. Total 200 metacercariae were collected from 50 gobies. In order to obtain adult worms two kittens and a puppy were infected each with 34-100 metacercariae, and total 33 adults were recovered between the day 4 and day 8 post-infection. The S. lari adults measured 0.95-1.18 mm long and 0.26-0.32 mm wide and the eggs in uteri 0.028-0.033 mm by 0.017-0.020 mm. The most characteristic morphological feature of these flukes was the presence of a gonotyl and gonotyl spines arranged in two groups; densely crowded group of 30-40 spines and linearly-arranged one of 30-40 spines, together of which made a comma (or reversed comma) shape along the lateral margin of the gonotyl. It has been proved by this study that S. lari is distributed in southern coasts of Korea.     

A survey of Enterobius vermicularis infection among children on western and southern coastal islands of the Republic of Korea

To determine the status of Enterobius vermicularis infection among children living on western and southern coastal islands of the Republic of Korea, children (3-10 years) in 39 kindergartens and primary schools were examined using the cello-tape anal swab method, during July and August 2000. Of 1,661 children examined, 307 (18.5%) were found to be positive for E. vermicularis eggs. The highest infection rate (59.3%) was found in a kindergarten and a branch school of Shinyang primary school on Chujado, Jeju-do (Province). Remarkable differences in egg positive rates were observed in different localities. The egg positive rate for boys (21.3%) was significantly higher than that of girls (15.4%) (P = 0.02). However, positive rates were not significantly dependent on age. The results of the present study show that E. vermicularis infection is highly prevalent among pre-school and primary school children living on the western and southern coastal islands of the Republic of Korea, and indicate the need for efforts to control this infection.     

Prevalence of zoonotic metacercariae in two species of grouper, Epinephelus coioides and Epinephelus bleekeri, and flathead mullet, Mugil cephalus, in Vietnam

Fishborne zoonotic metacercariae have not been reported from brackish water and marine fish from Vietnam waters although these parasites are common in the country's freshwater fish. Both wild-caught and cultured grouper (Epinephelus coioides and Epinephelus bleekeri), and mullet (Mugil cephalus) from brackish and marine waters located in Khanh Hoa province in central coastal Vietnam were examined, and found positive for zoonotic trematode metacercariae. From grouper, Heterophyopsis continua and Procerovum varium were recovered. The prevalence of H. continua ranged from 2.0 to 6.0% and that for P. varium ranged from 11.6 to 15.8%. Mullet were infected with Pygidiopsis summa and H. continua both of these species are new records for Vietnam. The prevalence of P. summa in mullet was generally high, ranging from 17.6 to 75.5%, and was significantly higher than the prevalence of H. continua (2.5 to 32.4%). There were no significant differences in the prevalence of metacercariae between grouper from natural or cultured habitats, indicating that the highest risk of infection occurs in the wild-caught state prior to their placement in culture. Further, there was no difference in metacercarial prevalence between the 2 species of grouper. Infected wild-caught seed were only observed from January to October. Monthly variation in prevalence suggests seasonal variation in mullet infections occurs in this region with the highest transmission taking place from October to December. Basic investigations on the ecology and epidemiology of these intestinal flukes need to be carried out to determine their significance as a public health problem and the aspects of their biology that may be vulnerable to control interventions.     

Stictodora lari (Digenea: Heterophyidae): the discovery of the first human infections

Stictodora lari Yamaguti, 1939 (Digenea: Heterophyidae) was originally reported as an avian intestinal parasite and is here reported in humans. The patients were adults, aged 46-69 (2 men and 4 women), who resided in coastal villages in Sachon-gun, Kyongsangnam-do, or Shinan-gun, Chollanam-do. in the Republic of Korea. The worms were recovered after praziquantel treatment and purgation with magnesium salts. A total of 15 S. lari specimens (1-10 per individual) was collected, together with 5 other species of intestinal flukes. The flukes were morphologically characterized by a small body size (0.70-0.86 mm long and 0.27-0.36 mm wide), a ventrogenital sac, and a gonotyl armed with 70-80 spines in the form of a comma or reversed comma lying along their lateral margin. The patients had eaten the raw flesh of mullets and gobies that had been caught in an estuary near their villages. To the best of our knowledge, this is the first record of a human S. lari infection.     

A nationwide survey of the prevalence of human Gymnophalloides seoi infection on western and southern coastal islands in the Republic of Korea

A nationwide survey was performed to know the distribution and prevalence of human Gymnophalloides seoi infection on western and southern coastal islands in the Republic of Korea. A total of 4,178 fecal specimens were collected from residents on 45 (24 western and 21 southern) islands, and examined by Kato-Katz and formalin-ether sedimentation techniques. Eggs of G. seoi were detected from 160 (3.8%) people living on 22 (13 western and 9 southern) islands. The prevalence varied by the location of islands; higher on western islands than on southern islands. The highest prevalence was found on Amtaedo (25.3%), followed by Cheungdo (25.0%), and Anchwado (20.9%) (Shinan-gun). A little lower prevalence was observed on Munyodo (13.3%), Shinshido (12.9%), and Sonyudo (10.3%) (Kunsan-shi). Of the remaining islands, the regions showing the prevalence greater than 5% included Kohado, Dallido (Mokpo-shi), Pyeongildo, Kogumdo (Wando-gun), and Keogumdo (Kohung-gun). A strong age predilection was noted (p < 0.05); 95% of the infected people were over 40 years old. Females showed a little higher prevalence than males. The results indicate that human G. seoi infection is more widely distributed than previously considered. Nine of 11 islands (excluding the 2 known areas Munyodo and Sunyudo) that showed greater prevalence than 5% are regarded as new endemic foci of G. seoi.     

Prevalence of Gymnophalloides seoi infection in coastal villages of Haenam-gun and Yeongam-gun, Republic of Korea

One coastal village in Haenam-gun and two in Yeongam-gun, Jeollanam-do were surveyed for intestinal parasite infections by fecal examination. The egg positive rates of Gymnophalloides seoi were high, 24.1% (14/58) in Haenam-gun and 9.3% (11/118) in Yeongam-gun. The egg positive rates of heterophyids, including Heterophyes nocens, and of Clonorchis sinensis were 10.3% and 6.9% in Haenam-gun, and 14.4% and 8.5% in Yeongam-gun, respectively. After praziquantel treatment and purgation, a total of 37,761 fluke specimens were recovered from 17 patients; 11 in Haenam-gun and 6 in Yeongam-gun. Gymnophalloides seoi was the most commonly recovered species, with 37,489 specimens in total (2,205 per person). Other recovered flukes included Heterophyes nocens, Stictodora fuscata, Heterophyopsis continua, Pygidiopsis summa, and undetermined species. These results indicate that the areas surveyed are new endemic foci of G. seoi.     

Surveys of Gynaecotyla squatarolae and Microphallus koreana (Digenea: Microphallidae) Metacercariae in Two Species of Estuarine Crabs in Western Coastal Areas, Korea

To figure out the geographical distribution of Gynaecotyla squatarolae and Microphallus koreana metacercariae in Korea, shore crabs of southwestern coastal areas were examined. Eight coastal areas in Inchon-si (A), Gyeonggi-do (B), Chungcheongnam-do (C, D, and E), Jeollabuk-do (F), and Jeollanam-do (G and H) were selected, and 2 kinds of crabs, Macrophthalmus dilatatus and/or Macrophthalmus japonicus, were caught. After transportation to the laboratory, 15 crabs per each group were grouped and ground in a mortar and pestle, and examined for microphallid metacercariae. In M. dilatatus, G. squatarolae metacercariae were recovered from 3 (C, E, and H) out of 6 regions, but M. koreana metacercariae were not recovered. In the case of M. japonicus, G. squatarolae metacercariae were recovered from 6 (B, D, E, F, G, and H) of 7 areas surveyed, and M. koreana matacercariae were detected from 5 regions (A, B, D, F, and H). These results indicate that the life cycle of G. squatarolae is maintained in the western coastal areas using M. dilatatus and M. japonicus as intermediate hosts, while that of M. koreana is maintained only using M. japonicus.     

Discovery of Gymnophalloides seoi metacercariae in oysters from islands of the West Sea known as the habitats of paleartic oystercatchers

An epidemiological survey was performed to know the infection status of oysters with Gymnophalloides seoi metacercariae in 7 islands of the West Sea known as the habitat of paleartic oystercatchers, Haematopus ostralegus osculans, in Korea. The surveyed areas were Aphaedo (Shinan-gun, Chollanam-do), Jangjado, Sonyudo and Munyodo (Okdo-myon, Kunsan-shi, Chollabuk-do), Yubudo (Changhang-up, Sochon-gun Chungchongnam-do), and Polumdo and Chumoondo (Sodo-myon, Kangwha-gun. Inchon-shi). The oysters collected from Aphaedo, the known endemic focus, were examined monthly from August 1995 to October 1996 for observation of any seasonal variation of the metacercarial density. The average metacercarial burden was 761-2,077 by month, but the seasonal variation of the metacercarial density was not obvious. A total of 54 metacercariae was detected in 63 oysters collected from Yubudo. Out of 30 oysters from Sonyudo, 25 (83.3%) were infected with 1-66 metacercariae (12.6 in average). All of 50 oysters (100%) from Munyodo were infected with 3-162 metacercariae (53.5 in average). Only 4 metacercariae were detected in 100 oysters from Chumoondo. However, no metacercariae were found in 55 oysters from Jangjado and 50 oysters from Polumdo. From the above results, it was confirmed that G. seoi is still highly prevalent in oysters from Aphaedo, and several islands of the West Sea known as the habitats of paleartic oystercatchers are new endemic areas of this fluke.     

Survey of Zoonotic Trematode Metacercariae in Fish from Water systems of Geum-gang (River) in Republic of Korea

The infection status of zoonotic trematode metacercariae (ZTM) was surveyed in freshwater fishes from the water systems of Geum-gang (River) in the Republic of Korea (Korea). A total of 1,161 freshwater fishes from 6 local sites of Geum-gang were examined with the artificial digestion method for 4 years (2012–2015). Clonorchis sinensis metacercariae were detected in 122 (37.2%) out of 328 fishes in the positive fish species from 4 surveyed areas, and their mean intensity was 43 per fish infected. Metagonimus spp. metacercariae were found in 432 (51.7%) out of 835 fishes in the positive fish species from all 6 surveyed areas, and their mean intensity was 30 per fish infected. Centrocestus armatus metacercariae were detected in 285 (75.0%) out of 380 fishes in the positive fish species from 6 surveyed areas, and their mean intensity was 2,100 per fish infected. Echinostoma spp. metacercariae were found in 56 (19.7%) out of 284 fishes in the positive fish species from 5 surveyed areas, and their mean intensity was 10 per fish infected. Clinostomum complanatum metacercariae were detected in 98 (57.3%) out of 171 fishes in the positive fish species from only 2 surveyed areas, and their mean intensity was 11 per fish infected. Conclusively, the endemicity of ZTM is not so high in fishes from water systems of Geum-gang in Korea although it is more or less different by fish species, surveyed areas and ZTM species.     

Gynaecotyla squatarolae (Digenea: Microphallidae) from rats experimentally infected with metacercariae from the shore crab, Macrophthalmus dilatatus

Metacercariae of Gynaecotyla squatarolae (Digenea: Microphallidae) were discovered from the shore crab, Macrophthalmus dilatatus, purchased at a market in a coastal town of Taean-Eup, Chungcheongnam-do, Republic of Korea. Their adult flukes were confirmed by experimental infection of rats. The metacercariae of G. squatarolae were elliptical (391.1 x 362.5 micrometer), and the excysted metacercariae had progenetic genital organs, including the ovary and testes. To obtain adult flukes, 6 Sprague-Dawley rats were fed 500 metacercariae each, and killed at days 2, 4, and 6 post-infection. The adult flukes were identified as G. squatarolae (Yamaguti, 1934) Yamaguti, 1939, based on morphological characters, including 2 ventral suckers (1 large and 1 small), a large genital atrium equipped with the cirrus and the metraterm, separated male and female genital pores, a transversely long cirrus pouch, and extensive vitelline follicles. In the present study, it has been first proven that the shore crab M. dilatatus is a second intermediate host for G. squatarolae in the Republic of Korea.     

Chinese Strains (Type 7) of JC Virus Are Afro-Asiatic in Origin But Are Phylogenetically Distinct from the Mongolian and Indian Strains (Type 2D) and the Korean and Japanese Strains (Type 2A)

We have further characterized the Asian genotypes (Types 2 and 7) and subtypes of JC virus (JCV). Urine samples from 224 individuals with Han and Mongolian populations were collected in five regions in eastern China: Kunming, Chengdu, Shenyang, Chifeng, and Manzhouli. Also, 99 urine samples were collected from coastal and hill groups in Kerala, southern India, and 23 urine samples from Seoul, Korea. PCR products of four typing fragments were sequenced, including two in the VP1 gene, as well as one each in the VT intergenic region and regulatory region. It was possible to clone and sequence a total of 42 JCV whole genomes (~5120 bp). Five genotypes of JCV (Types 7A, 7B, 7C, 2D, and 4) were found in China, four genotypes (Types 2D, 7C, 4, and 1B) in southern India, and three genotypes (Types 7B, 2A, and 1A) in Korea. Type 7A was most prevalent in South China (59–64%) and Type 7B was predominant in northeast China and Inner Mongolia (67–77%). Type 7C strains were spread throughout North and South China (3–14%), while Type 2D strains were found only in the two Mongolian groups (9–10%). In southern India, Type 2D was predominant in the coastal group (95%), and two major types, Type 7C (50%) and Type 2D (35%), were prevalent in the tribal hill groups. In Korea two major genotypes were found: Type 7B (50%) and Type 2A (43%). Phylogenetic reconstruction places the Chinese genotypes in the Afro-Asiatic supercluster, but distinct from the Mongolian and Indian strains (Type 2D), as well as the Korean and Japanese genotype (Type 2A) that predominates in the Americas.