Abstract:The prevalence of liver and intestinal fluke infections was surveyed on residents of Savannakhet Province, Laos. Fecal specimens were collected from a total of 981 residents in 4 Mekong riverside villages and examined by the Kato-Katz thick smear technique. The results revealed that the overall helminth egg positive rate was 84.2%, and the positive rate for small trematode eggs, including Opisthorchis viverrini, heterophyids, or lecithodendriids, was 67.1%. To obtain adult flukes, 38 small trematode egg positive cases were treated with a 20-30 mg/kg single dose of praziquantel and purged. Diarrheic stools were then collected from 29 people and searched for helminth parasites using stereomicroscopes. Mixed infections with O. viverrini and 6 kinds of intestinal flukes were found, namely, Haplorchis taichui, Haplorchis pumilio, Haplorchis yokogawai, Prosthodendrium molenkampi, Phaneropsolus bonnei, and echinostomes. The total number of flukes collected was 7,693 specimens (av. no. per treated person; 265.3). The most common species was O. viverrini, followed by H. taichui, P. molenkampi, echinostomes, H. pumilio, P. bonnei, and H. yokogawai. The results indicate that foodborne liver and intestinal fluke infections are prevalent among residents of Savannakhet Province, Laos.

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An epidemiological survey was performed to know the status of Cryptosporidium sp. infection among the people in Seoul and Chollanam-do in 1992. One village of Chollanam-do (Hwasun-gun) which showed the highest oocyst positive rate was re-surveyed in 1995 for human infection and for cattle also. The subjected areas consisted of 8 urban villages ( = dongs) of Seoul and 4 urban ( = dongs) and 7 rural ( = myons) villages of Chollanam-do. A total of 3,146 fecal samples was collected randomly, and smears were made from formalin-ether sediments. They were examined for Cryptosporidium oocysts by modified acid fast staining. The overall oocyst positive rate was 7.9% (248/3,146), but the rate was remarkably different between Seoul and Chollanam-do, 0.5% (4/853) and 10.6% (244/2,293), respectively. The average size of oocysts was 4.8 +/- 0.5 by 4.2 +/- 0.5 microns, compatible with C. parvum. In Chollanam-do, rural villages showed significantly higher rate (14.0%) than urban villages (3.7%). Especially the people in Iyang-myon. Hwasun-gun, a typical rural village, revealed a very high rate of 40.0% (74/185). Adults aged 51-70 years revealed the highest positive rate among all age groups. At the re-survey of the same village of Hwasun-gun in 1995, 44 (35.2%) of 125 villagers and 14 (93.3%) of 15 cattle examined were positive for C. parvum oocysts. The results suggest that C. parvum is highly prevalent in rural areas of Chollanam-do, and an important source or mode of infection seems to be contaminated water or contact with the feces of infected cattle.

Acanthoparyphium tyosenense Yamaguti, 1939 (Digenea: Echinostomatidae), was originally reported as an avian intestinal parasite; here, its presence is reported in 10 humans in the Republic of Korea. The patients were 9 adults aged 35-66 yr (males and females) and a young girl aged 7 yr residing in 2 coastal villages in Puan-gun, Chollabuk-do. The worms were recovered after treatment with praziquantel and purgation with magnesium salts. A total of 158 specimens (1-107 specimens/individual) was collected, together with varying numbers of other intestinal flukes. The patients had eaten various kinds of brackish water mollusks caught in an estuary near their villages. Five bivalves and a gastropod species suspected as sources of human infection were collected and examined. Two bivalves (Mactra veneriformis and Solen grandis) and the gastropod (Neverita bicolor) were found to be infected with the metacercariae of A. tyosenense; adult flukes were confirmed after the experimental infection of chicks. The results show that A. tyosenense infects humans and that brackish water mollusks are the source of human infection.

Abstract. The prevalence of Cryptosporidium parvum infection and its seasonality were studied in a small rural village occupied predominantly by aged people in Hwasun-gun, Chollanam-do, Republic of Korea. Fecal samples were collected monthly from November 1996 to October 1997 and examined for enteric parasites. To detect oocysts of C. parvum, the modified acid-fast stain was applied. To determine effects of climatic factors, local weather reports were collected. The overall oocyst prevalence during 1 year was 57.0% (77 of 135), and was significantly higher (P Ͻ 0.0001) in aged people-those aged 50-59 years (80.0%) and those aged 60-69 years (69.0%)-than in younger groups. No significant difference (P Ͼ 0.05) was noted between men and boys (53.6%) and women and girls (59.5%), but significant (P Ͻ 0.05) household clustering was recognized. People aged Ͼ 50 years tended to be more repeatedly positive than people in the younger group. The rate varied monthly from 7.8 to 20.0% (average, 12.6%), with significantly higher (P Ͻ 0.05) rates in spring than in summer and winter months. This seasonality had little relation with temperature (r ϭ 0.04), but a weak correlation was found with rainfall (r ϭ 0.4). It is of special interest that cryptosporidiosis is highly endemic among the aged population.