• Parasites, Hosts and Diseases
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• v.27 no.1
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• pp.47-56
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• 1989

Some biological characteristics of Centrecestus armatui were studied using albino rats as its experimental host. The metacercariae were collected from Zacco Platypus by artificial digestion method. Laboratory rats(Wistar) were fed each 100 or 200 metacercariae and sacrificed on 1, 2, 3, 4, 5, 6, 8, 14 and 28 days after infection to recover worms of various ages. The average recovery rate was 10.7% from 82 rats. The rate decreased rather slowly for the first 8 days but showed a steep decrease thereafter. Of the worms, 35.5% were recovered from the duodenum and 62.5% from the jejunum. At metacercarial stage, body length was $293{\mu\textrm{m}}$ and body width $144{\mu\textrm{m}}$. At adult stage, the length and width reached $382{\mu\textrm{m}}$ and $214{\mu\textrm{m}}$ respectively at 14 days after infection. The testes and Mehlis' gland were recognized at metacercarial stage, whereas the ovarian anlage appeared on the 1st day of infection, seminal vesicle and vitellaria on the 2nd day, and seminal receptacle and uterine eggs on the 3rd day. Until 8 days after infection the genital organs developed continuously and the number of uterine eggs increased. The above results show that albino rats are one of useful experimental hosts for C. armatus and the worms can develop to adults in 3 days after infection.

• Parasites, Hosts and Diseases
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• v.58 no.1
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• pp.67-72
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• 2020

Human infection with Echinostoma aegyptica Khalil and Abaza, 1924 (Trematoda: Echinostomatidae) is extremely rare. In this study, we confirmed E. aegyptica infection in 5 riparian residents living along the Mekong River in Savannakhet Province, Lao PDR. The patients revealed eggs of Opisthorchis viverrini/minute intestinal flukes, echinostomes, and other parasites in fecal examinations using the Kato-Katz technique. Following treatment with praziquantel 30-40 mg/kg and pyrantel pamoate 10-15 mg/kg in a single dose and purging with magnesium salts, adult specimens of various helminth species were collected. Among the trematodes, echinostome flukes of 4.5-7.6 mm in length (n = 134; av. 22.3 specimens per case) were of taxonomic interest and subjected in this study. The flukes were morphologically characterized by having total 43-45 collar spines arranged in 2 alternating rows (corner spines usually 5 on each side) and compatible with previous descriptions of E. aegyptica. The patients were mixed-infected with other helminths, so specific clinical manifestations due to this echinostome fluke were difficult to determine. The present paper describes for the first time human E. aegyptica infections in Lao PDR. This is the second report of human infection (2nd-6th cases) with E. aegyptica in the world following the first one from China.

• Parasites, Hosts and Diseases
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• v.36 no.3
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• pp.155-162
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• 1998

Two endemic foci of heterophyid infections were discovered in coastal villages of Puan-gun. Chollabuk-do, and Sachon-gun. Kyongsangnam-do, Korea. Fecal examina- tions were performed on 153 inhabitants of Puan-gun and 138 of Sachon-gun, using cellophane thick smear and formalin-ether sedimentation technique. The helminth egg and/or protozoan cyst positive rate was 21.5% (33/153) in Puan-gun and 39.1% (54/138) in Sachon-gun. In Puan-fun, the egg Positive rate of heterophyids was the highest, 17.6%, and that of other parasites was 0.7-2.6% by parasite species. In Sachon-gun, that of heterophyids wa's 18.8%, followed by Clonorchis sinensis (12.3%). and other parasites (0.7-5.OBEI . Twenth-two (Puan-gun) and six (Sachon-gun) heterophyid egg Positive cases were treated loth praziquantel, and adult flukes were collected from their diarrheic stools. A total of 3,284 adult flukes of Heterophyes nocens was collected from all of the 22 patients treated in Puan-gun (3-778 individually) , and other trematodes were also collected from 2- 15 patients; Ftgidiopsis sumac, Stellcntchcsmus JcEcctus, Metogoninus Wokogaupci, M. miyntci, Stictodora Juscnta, Heterophwopsis continua, Acnnthopcrwphium kurognmo, and GWmnophaELoines seoi. In Sachon-gun, M. yokognwci (3,007 specimens), H. nocens (120), aud S. falcatus (46) were collected from 5 of 6 treated patients, and H. continuo and 5. tan each from one patient. The present study revealed that heterophyid flukes, especially If. nocens and M. Wokofowai, are prevalent in the southern and western coastal areas of Korea where fresh and/or brackish water fishes are popularly eaten raw.

• Parasites, Hosts and Diseases
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• v.31 no.2
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• pp.109-116
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• 1993

Worm recovery rates and pathologic changes in small intestine of albino rats were observed after concurrent and challenge infections with metacercariae (MCI of Fibricota seouLensis and MetaBonimus vokogaupci, and compared with those of single Infection groups. Albino rats In concurrent Infection group were killed 20 days after feeding with 1,000 MC of each fluke. Rats in challenge. infection group were fed with 1.000 MC of f seouleni,s and challenged by 1,000 MC of M. yokogawai 10 days after primary infection, then killed 10 days thereafter. In concurrent infection group, mean number of F. seoulensis and M. yokogawai recovered, 250 and 118 respectively, were similar to those of single infection groups. However, more flukes were collected from the duodenum and less flukes were from the ileum than from single infection group. In challenge Infection group, the recovery rate of F. seoulensis was similar to that of sin91e infection group and the distribution of thIn flukes was similar to that of concurrent infection group. Mean number of M. yokogculat, 69, was signiflcantly lower than that of single infection group. Its distribution, however, extended to the duodenum and most of the flukes were recovered from the jejunum. In concurrent infection group, villi of the duodenum were more markely thickened, fused and shortened than those in F. seoulensis sing1e Infection group. The crypt epithelium appeared to be hyperplastic and inflammatory cell infiltration into the villous stroma was mild. Villous atrophy in the jrlunum and ileum was ndlder than in M. yokogawai single infection group. In challenge Infection group, the fhldlngs were simuar to those of concurrent Infection group. Crypt epithelium hyperplasla was not severe in duodenum. Inflammatory reaction was observed in submucosa of the Jrjunum and ileum. From the above results, it Is considered that F. seoulenis ikabiting in upper part of small intestine affect the settlement of M. yokoguwai introduced later In lower part of the intestine.

• Parasites, Hosts and Diseases
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• v.23 no.1
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• pp.24-32
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• 1985

The worm development and egg laying pattern of Echinostoma hortense (Trematoda; Echinosto-matidae) were studied in albino rats and the brief clinical course was observed in human volunteers. A total of 21 rats were infected with 20~69 metacercariae each and two humans were with 7 and 27 metacercariae, which were collected from the loaches. For recovery of worms, the rats were sacrificed at irregular intervals from the 6th to 150th day after infection and the human volunteers were treated with praziquantel and purged with magnesium salt on the 26~27th day. The stools of the rats and humans were examined for the eggs. The results were as follows: 1. The worm recovery rate from the rats was not affected by the increase of infection time but varied individually; 9.1~50.0% (31.1 % in average). From humans, 14.3% and 37.0% (32.4% in average) of challenged were recovered. 2. In the rats, it was revealed that the worms rapidly grew for the first 14 days to become 7.59mm in average length and 1.17mm in average width but the growth became much slower thereafter until the 150th day; 7.95mm in length on the 21 th day, 9.04mm on the 28th day, 10.21mm on the 49th day and 12. 62mm on the 150th day. During the early stage of infection, the growth of genital organs (male or female) was expressed as sigmoid curves whereas non-genital organs (such as suckers) was simply as straight lines. 3. The prepatent period of this fluke was 10~12 days in the rats and 16~17 days in men. After the start of oviposition, the egg production by the worms remarkably increased, reached maximum on the 32~33th day, followed by decrease thereafter. The maximum value of E.P.G./worm was 390. 4. The major subjective symptoms in human volunteers were abdominal pain and diarrhea during the early stage of infection. The results show that human is as susceptible as the rats to E. hortense infection and the amount of egg production in the rats is greatly affected by the age of worms.

• Parasites, Hosts and Diseases
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• v.23 no.1
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• pp.123-139
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• 1985

The present survey was undertaken to observe the geographical distibution of matacercaria among the sweetfish, Plecoglossus altivelis, the most important second intermediate host of Metagonimus yokegawai, which were collected during the period from 1983 to 1984 in south-eastern coastal areas of Korea. The results obtained were summarized as follow: 1. A total of 668 sweetfish collected from 70 chins (=streams) in the above coastal arcus was examined for the metacercariae, and 432 (64.7%) 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. 2. It was observed that the mean infection rate showed 46.45 in Gangweon-Do (=province) . The infection rates varied from stream to stress showing 100% in Namdae stream(Gangnun-city) , Obsib stream (Samchok-gun) and Dongmak, 95.0% in Hosan stream, 90.0% in Gungchin stream, and Namdae stream (Yangyang-fp) ,80.0% in Hwasang stream,50.0% in Daebong stream,45.0% in Yonghwa stream, 30.0% in sangchsn stream and Sachsn stream, 20.0% in Munam stream and Okgyoe stream, 15.0% in Imweon stream, 10.0% in Namchsn stream. And no metacercarial infections in their fish host were found in the areas of Mulchi stream, Sangun stream, Gosamun stream, Jonchon stream and Gagok stream. 3. It was observed that the mean infection rate showed 50.9% in Kyangsangbuk-Do (=province). The infection rates also varied from stream to stream showing 100% in Songchon stream, Osib stream (Yongdok-gun) and Daejong stream,60.0% in Pyanghae stream and Gunmu stream,50.0% in Buhwung stream and stream, 25.0% in Nagok stream, 20.0% in Oangbi stream, 10.0% in Namhodong stream. And no metacercarial infections in their fish host were found in the areas of Namdae stream (Uljinup) and Chaksan stream. 4. It was observed that the mean infection rate showed 67.6% in Kyangsangnam-Do(=province). The infection rates varied from stream to stream showing 100% in Taehwa river, Hwiya river, Inchfn stream, Miryang river, Nam river, Hwagae stream, Koha stream, Sosang stream, and Tongchon stream,90.9% in Yancho stream,90.0% in Hoihwa stream,80.0% in Chindong stream, 66. YoA in Chingyo stream, 40.0% in Hoyam river. And no metacercarial infections in their fish host were found in the areas of Chinjon stream, Sanchan stream and Jukch6n stream. 5. It was observed that the mean infection rate showed 94.6"A in 0h511anam-Do(=province). The infection rates varied from stream to stream showing 100% in DongchEn stream, Isachon stream, Somjin river(GoksEng-gun) , Ssmjin river(Kurye-gun) , S6si stream, Gokchsn stream, Kohung stream, Kwansan stream, Youi stream, stream, Unj6n stream and Apnae stream, 92.3% in Tamjin river, 90.9% in Okkok stream, 84.6% in Songgen stream. And no metacercarial infections in their fish host were found in the area of Ypmgpl stream. 6. On the other hand, the infection rate showed 100% in Inchsn river of Chollabuk Do (=province) (=province) and Kangsn stream of Cheju-Do(=province) .