The metacercariae of Metagonimus yokogawai were isolated from the sweetfish Plecoglossus altivelis, clollected at Hwagae, South Kyongsang Do, one of the newly known endemic foci of metagonimiasis in Korea. The body structure of metacercaria of M.yokogawai was described and the measurements of the excysted metacercaria were also made. In order to know the distribution of metacercariae within the host, the rate of infection and the intensity of infection, a total of 10 sweet fishes was examined and it was found all infected, from which a total of 38,511 metacercariae was isolated. The number of metacercariae in a fish varied from 219 to 14,427. The average number of metacercaria per fish was 3,851. The distribution of metacercariae in the four divided parts of fish was observed in the following order; number of metacercaria in the muscles; 2,417 (62.8%), in the subcutaneous tissues; 1,126.9 (29.3%), and on the scale; 291.9(7.7%). The development of the metacercaria of M. yokogawai in the mouse host was experimentally traced every day for 10 days after infection . In an earlier period of infection, the growth rate of the genital primordia was distinctly high, particularly in the testes. The seminal receptable and seminal vesicle became clearly recognized in measurable size at 4 days after infection. The vitelline follicles and their ducts were also first visible in the living specimens at 6 days after infection. The oral sucker was larger in size than the ventral sucker in an early stage of the worms, however after 7 days after infection it reversed. The posterior part of body began to extend since two days after infection. Fully matured worms were able to collect only after 7 days after infection. At this stage, the body of worm became 0.7 mm long and 0.3 mm wide. The first positive appearance of eggs in the uterine tubule and in feces was on the 6th day and 10th day of infection, respectively. In an earlier stage of infection, the worms were found mostly in the upper portion of small intestine and the recovery rates of the worms were high, however according to the course of infection in later stage they were seen rather in the lower part of the intestine and the recovery rate also decreased.
parasitology-helminth-trematoda ; Metagonimus yokogawai ; development ; metacercaria ; Plecoglossus altivelis

An epidemiological investigation was conducted on Metagonimus yokogawai infection in Hadong Gun (County), Gyeongsang Nam Do, Korea, and following findings were obtained. Overall prevalence rate of Metagonimus yokogawai infection was 29.1 percent from a total of 1,163 inhabitants examined. By area of river and stream, Seomjin-gang R.: 9.5 percent (out of 95 inhabitants examined) in Jeondo Ri in the lower river, 19.9 percent (156) at Dugog Ri near Hadong town, and 90.8 percent (65) in Tab Ri of Hwagae Myeon where Hwagae-cheon Stream joins; Hwagae-Cheon Stream: 42.2 percent (45) in Yonggang Ri of the middle stream and 27.5 percent (72) in Daeseong Ri of the upper stream; Hoengcheon-gang R.: 54.7 percent (161) in Gojeol Ri of the lower river, 40.6 percent (128) in Hoengcheon Ri of the middle stream, and 5.4 percent (93) in Jungi Ri of the upper stream, and 43.8 percent (89) in Uge Ri located along a tributary of the Hoengcheon-gang R. and 4.0 percent (101) in Jangam Ri which is located about 4 km away from the river; Deogcheon-gang R.: 18.5 percent (54) in Munam Ri; Gwangog-cheon Stream: 2.8 percent (107) in Gwangog Ri. The difference in prevalence rate of the infection by area was correlated with the opportunity and amount of raw eating of sweetfish by the inhabitants in the respective areas. By age and sex, the overall prevalence rate increased from young age group and reached a peak at 20-29 age group and then the rate decreased gradually. In high endemic areas, however, a peak level of the rate lasted up to 40-49 age group in male. On the other hand, in low endemic areas, the rate was significantly lower in female, though moderate level of the infection was seen in male. The overall prevalence rate was higher in male than in female and the difference was greater in middle age groups. The most significant mode of infection by the inhabitants was the raw eating of sweetfish which commonly harbour metacercariae of M. yokogawai during summer through autumn. Besides, it was noted that the infection can be acquired through contamination with the metacercariae on food of various side-dish and kitchen utensils as well as on hands of a cook when such fish are prepared or handled. The inhabitants usually begin to acquire infection from early June of a year when fishing of sweetfish opens and acquire infection more frequently in July and August when fish are caught more productively and favored for raw consumption by inhabitants. From September, sweetfish are no more favored for raw consumption and accordingly are dried and cooked in this season. The infection in the sweetfish Plecoglossus altivelis as the second intermediate host was first observed from May with low level of infection and the intensity of infection in a fish rapidly increased until reaching a peak in October when sweetfish season normally ends. The first intermediate host snail of M. yokogawai in this area was Semisulcospira coreana (Martens) which is widely distributed in the streams and rivers in this locality.
parasitology-helminth-trematoda ; Metagonimus yokogawai ; metacercaria ; Plecoglossus altivelis ; epidemiology

There are a number of eating-houses in the basin of river Ahnseong that sell rawsweetfish, Plecoglossus altivelis, to local residents and visitors. These facts called attention to the possibility of wide spread of metagonimiasis in that area. In an attempt to determine whether the metacercaria of Metagonimus yokogawai does present in the sweetfish caught in the river Ahnseong, a total of 77 fish were examined in the period from April to September 1978. All the fish were infected with the encysted larvae. The average number of larvae persweetfish was 1,815, of which the metacercaria rate for the fluke in the flesh was 56.9 per cent and in the scale, 30.5 per cent. These results indicate that all the sweetfish in the river Ahnseong harbour the metacercaria of Metagonimus yokogawai.
parasitology-helminth-trematoda ; Metagonimus yokogawai ; metacercaria ; Plecoglossus altivelis ; epidemiology

This study was carried out to outline the geographical distribution of the sweetfish which were infected by the metacercariae of Metagonimus yokogawai from August to October in 1979. The infection status was examined both by the muscle compression method and by digestion technique. The result was summarized as follows: A total of 197 sweetfish, Plecoglossus altivelis was collected, 125 fish from 5 streams along the East Coast and 72 fish from 4 streams along the South Coast. Total 125(63.5 percent) fish were infected by the metacercariae of M. yokogawai. The rate and intensity of infection in the south coastal areas were much higher than those in the east coastal areas; the rate was 42.4 percent in the East and 100 percent in the South, mean number of metacercariae per fish was 721 in the East and 14,308 in the South, and mean number of metacercariae per gram of flesh was 43 in the East compare with 904 in the South. The sweetfish infected by the metacercaria of M. yokogawai were newly observed in 5 foci, i.e., Yeongogcheon in Myeongju Gun and Namdaecheon in Gangneung Si, Gangweon Do and Wangpicheon in Uljin Gun, Gyeongsangbug Do in the East, and a branch of Namgang in Euiryeong Gun and Sinhyeoncheon in Geoje Gun, Gyeongsangnam Do in the South. The rate of metacercarial infection was 4.1 percent in Yeongogcheon and 100 percent in others. The number of metacercariae in a fish ranged from 9 to 45,018 and the number of metacercariae per gram of flesh was the lowest in Gangneung Namdaecheon as 19 and the highest in Geoje Sinhyeoncheon as 1,237. Summarizing these findings with previous records, M. yokogawai might be prevalent in the streams along the East Coast southern from Myeongju Gun, Gangweon Do and along the South Coast in Korea.
parasitology-helminth-trematoda ; Metagonimus yokogawai ; sweetfish-Plecoglossus altivelis-epidemiology ; metacercaria

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.
parasitology-helminth-trematoda ; Metagonimus yokogawai ; epidemiology ; Plecoglossus altivelis

P. altivelis from Korea republic is recorded as a new host for H. continua which is described and figured.
parasitology-helminth-trematoda ; Heterophyopsis continua ; Plecoglossus altivelis ; host

The present survey was undertaken to observe the geographical distribution of metacercaria among the sweetfish, Plecoglossus altivelis, the most important second intermediate host of Metagonimus yokogawai, which were collected during the period from 1983 to 1984 in south-eastern coastal areas of Korea. The results obtained were summarized as follows: A total of 668 sweetfish collected from 70 chons (=streams) in the above coasta1 areas was examined for the metacercariae, and 432(64.7 percent) among them were infected with metacercariae of M. yokogawai. The mean number of metacercariae in a fish was in the range from 0 to 29,604 and the mean number of the metacercariae in a fish was 640.3. It was observed that the mean infection rate showed 46.4 percent in Gangweon-Do (=province). The infection rates varied from stream to stream showing 100 percent in Namdae stream(Gangnun-city), Obsib-stream(Samchok-gun) and Dongmak, 95.0 percent in Hosan stream, 90.0 percent in Gungchon stream, and Namdae stream (Yangyang-up), 80.0 percent in Hwasang stream, 50.0 percent in Daebong stream, 45.0 percent in Yonghwa stream, 30.0 percent in Sangchon stream and Sachon stream, 20.0 percent in Munam stream and Okgyoe stream, 15.0 percent in Imweon stream, 10.0 percent in Namchon stream. And no metacercarial infections in their fish host were found in the areas of Mulchi stream, Sangun stream, Gosamun stream, Jonchon stream snd Gagok stream. It was observed that the mean infection rate showed 50.9 percent in Kyongsangbuk-Do(=province). The infection rates also varied from stream to stream showing 100 percent in Songchon stream, Osib stream (Yongdok-gun) and Daejong stream, 60.0 percent in Pyonghae stream snd Gunmu stream, 50.0 percent in Buhwung stream, 25.0 percent in Nagok stream, 20.0 percent in Oangbi stream, 10.0 percent in Namhodong stream. And no metacercarial infections in their fish host were found in the areas of Namdae stream (Uljinup) and Choksan stream. It was observed that the mean infection rate showed 67.6 percent in Kyongsangnam-Do(=province). The infection rates varied from stream to stream showing 100 percent in Taehwa river, Hwiya river, Inchon stream, Miryang river, Nam river, Hwagae stream, Koha stream, Sosang stream, and Tongchon stream, 90.9 percent in Yoncho stream, 90.0 percent in Hoihwa stream, 80.0 percent in Chindong stream, 66.7 percent in Chingyo stream, 40.0 percent in Hoyam river. And no metacercarial infections in their fish host were found in the areas of Chinjon stream, Sanchon stream and Jukchon stream. It was observed that the mean infection rate showed 94.6 percent in Chollanam-Do(=province). The infection rates varied from stream to stream showing 100 percent in Dongchon stream, Isachon stream, Somjin river (Goksong-gun), Somjin river (Kurye-gun), Sosi stream, Gokchon stream, Kohung stream, Kwansan stream, Youi stream, Unjon stream and Apnae stream, 92.3 percent in Tamjin river, 90.9 percent in Okkok stream, 84.6 percent in Songgun stream. And no metacercarial infections in their fish host were found in the area of Yongok stream. On the other hand, the infection rate showed 100 percent in Inchon river of Chollabuk-Do (=province) and Kangon stream of Cheju-Do (=province).
parasitology-helminth-trematoda ; Metagonimus yokogawai ; epidemiology ; Plecoglossus altivelis

This study was performed to observe the chronological changes in the tegumental structure of M. yokogawai using scanning electron microscope. The subjected worms were excysted metacercariae obtained from sweetfish, and 2-day, 1-week and 4-week old worms experimentally reared in albino rats. The results are as follows: The tegument of excysted metacercariae showed many transverse shallow rugae, which were more remarkable in posterior half body, i.e., posterior to ventral sucker. The whole surface was armed with many scale-like spines; 7-8 pointed ones on anterior body and 2-3 pointed on posterior body. The ciliated knob-like papillae (Type I) were abundant around oral and ventral suckers, which grouped 2, 3 or 4 in number in most cases. A few round swellings of tegument (Type II) were observed only on oral sucker. The tegumental surface of 2-day old worms showed deeper rugae, and the anterior half covered with knob-like processes of distal cytoplasm and the posterior half with cobblestone-like ones. Interspinous space became more wide and 9 pointed spines appeared on anterior dorsal surface. The sensory papillae enlarged but not changed in their distribution. The tegument of 1-week old worms revealed knob-like cytoplasmic processes in posterior half body and velvety ones around oral sucker. The scale-Iike spines of anterior half body changed remarkably to the slender ones of posterior body at the level of ventral sucker. In dorsal surface, the arrangement of the Type I papillae were bilaterally symmetrical. The tegument of 4-week old worms were finely differentiated and the posterior tegument covered with velvety cytoplasmic processes. The spines had remarkably grown in length and width but the density remained nearly unchanged. The papillae also became larger but their morphology and distribution were not different from younger worms. However, the round elevation of cytoplasmic ridges (Type III papilla) appeared bilaterally on inner wall of oral sucker, approximately 8 in number. From the above results, it is considered that the tegument of juvenile M. yokogawai continued to differentiate until 4 weeks after infection.
parasitology-helminth-trematoda ; Metagonimus yokogawai ; electronmicroscopy ; Plecoglossus altivelis ; tegument

In order to determine the intensity of infection with the encysted larvae of Metagonimus yokogawai among Plecoglossus altivelis, sweetfish, caught at the rivers in Kyungpook Province, Korea were examined in the period from July to October, 1976. The data were compared with the results obtained from Tribolodon hakonensis, the sea-run dace, caught at the river Hyungsan in the Province. A total of 128 Plecoglossus altivelis were examined. All the fish were infected with the metacercaria of Metagonimus yokogawai. The metacercarial rate for the fluke in the flesh was higher than the rates in the fins and scales. The average number of larvae per sweetfish was 4,333, compared with the average of 1,541 from the sea-run dace. It was found that the highest number of encysted larvae was found in the flesh of sweetfish, whereas it was encountered on the scales of sea-run dace. In the distribution pattern of the cysts, there was no relationship between the size of fish and the intensity of infection.
parasitology-helminth-trematoda ; Metagonimus yokogawai-epidemiology ; Plecoglossus altivelis ; Tribolodon hakonensis ; metacercaria

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.
parasitology-helminth-trematoda ; Metagonimus yokogawai ; epidemiology ; metagonimiasis ; human ; Plecoglossus altivelis ; Leuciscus sp.