Excavations at two sites dating from BC-1900

A small coastal village of Muan-gun, Chollanam-do, was surveyed for intestinal fluke infections, especially heterophyids such as Heterophyes nocens and Pygidiopsis summa by fecal examination on 108 inhabitants. The egg positive rate of heterophyids was very high, 75.0%, and that of other parasites was comparatively low, 0.9-3.7% by parasite species. After treatment of 20 patients showing high E.P.G. with praziquantel and purging with MgSO4, total 3,864 specimens of H. nocens were collected from the diarrheic stools of all the patients treated (3-1,338 individually) and total 703 P. summa were harvested from 18 patients (1-170 individually), together with several other species of flukes. Other flukes included Stictodora fuscata (164 specimens from 4 patients), Heterophyopsis continua (2 from 2 patients), and Gymnophalloides seoi (4 from 3 patients). From this study, the surveyed coastal area of Muan-gun, Chollanam-do was proven to be a new endemic focus of H. nocens and P. summa. The occurrence of a few infected cases suggests that this area should also be a low-grade endemic area of S. fuscata, H. continua, and G. seoi.

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To determine the distribution and prevalence of heterophyid fluke infections on coastal islands of the Republic of Korea, fecal specimens were collected from 4,179 people residing on 45 islands in the West (Yellow) and South Seas and examined using the formalin-ether and Kato-Katz techniques. Eggs of Heterophyes nocens were found in 459 (11.0%) residents of 42 islands, with an average number of eggs per gram (epg) of feces of 79.6. Eggs of Pygidiopsis summa were found in 49 (1.2%) on 12 islands, with an average epg of 253.0. The egg-positive rate for H. nocens was the highest on Chungdo (32.6%), followed by Imchado (27.3%); P. summa was most prevalent on Imchado (15.2%). The majority (78.9% [362 of 549] of those infected with H. nocens and 81.6% [40 of 49] of those infected with P. summa) of those infected were adults more than 40 years old. Adult flukes of these species were recovered from residents of Imchado by treatment with praziquantel and purgation. Our results indicate that H. nocens and P. summa are indigenous to the southern and western coastal islands of the Republic of Korea.

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Abstract: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.

Abstract:The Tamjin River which flows from Jangheung-gun via Gangjin-gun to the South Sea was reported to be a highly endemic area of Metagonimus yokogawai infection in 1977 and 1985. However, there were no recent studies demonstrating how much change occurred in the endemicity, in terms of prevalence and worm burden, of metagonimiasis in this river basin. Thus, a small-scale epidemiological survey was carried out on some residents along the Tamjin River basin in order to determine the current status of M. yokogawai infection. A total of 48 fecal samples were collected and examined by the Kato-Katz thick smear and formalin-ether sedimentation techniques. The egg positive rate of all helminths was 50.0%, and that of M. yokogawai was 37.5%, followed by C. sinensis 22.9% and G. seoi 4.2%. To obtain the adult flukes of M. yokogawai, 6 egg positive cases were treated with praziquantel 10 mg/kg in a single dose and purged with magnesium sulfate. A total of 5,225 adult flukes (average 871 specimens per person) of M. yokogawai were collected from their diarrheic stools. Compared with the data reported in 1977 and 1985, the individual worm burdens appeared to have decreased remarkably, although the prevalence did not decrease at all. It is suggested that the endemicity of M. yokogawai infection along the Tamjin River has been reduced. To confirm this suggestion, the status of infection in snail and fish intermediate hosts should be investigated.

Susceptibility of inbred mouse strains to Metagonimus yokogawai, Metagonimus miyatai, and Metagonimus takahashii infections was studied using BALB/c, ddY, C57BL/6J, C3H/HeN, and A/J mice, with H-2 haplotypes d, s, b, k, and a, respectively. Two hundred metacercariae were orally fed to each mouse, and the worm recovery rates (WRR), worm dimensions, and intrauterine egg numbers were measured at days 3, 7, 14, 21, and 28 postinfection (PI). On day 14 PI, the WRR of M. yokogawai was highest in ddY mice (average, 62.2%); those of M. miyatai and M. takahashii were highest in ddY (19.5%) and BALB/c mice (10.4%), respectively; worm maturation was best in C3H/HeN (M. yokogawai), C57BL/6J (M. miyatai), and ddY mice (M. takahashii). All mouse strains showed higher susceptibility to infection with M. yokogawai than with M. miyatai or M. takahashii. The results show that susceptibility of mice to Metagonimus infection varies according to mouse strain and parasite species but is suggested to be independent of the mouse H-2 haplotype.