Egg Positive Rate Research Articles

Prevalence and risk factors for enterobiasis among preschool children in a metropolitan city in Korea.

The infection rate of Enterobius vermicularis was investigated in 1,191 preschool children in 25 daycare centers in Seoul, Korea by cellotape anal swab from July to August 1999. Both the directors of the daycare centers and the children's parents were asked to complete questionnaires that inquired about the potential risk factors involved. The overall egg positive rate for E. vermicularis was 9.5%, and the prevalence in the daycare centers ranged from 0 to 31.1%. Children aged 6-7 years showed a significantly higher egg positive rate than younger children, but the infection rate was similar for boys and girls. The socioeconomic status of the family and personal hygiene were not associated with enterobiasis, but anthelmintic medication significantly reduced the infection rate. The daycare centers in residential areas showed significantly lower egg positive rates than those situated near traditional markets. The environment of daycare centers is an important factor in enterobiasis, and the mass screening and treatment of children at high risk is recommended.

Egg positive rate of Enterobius vermicularis of primary school children in Geoje island.

The status of pinworm (Enterobius vermicularis) egg positive rate of primary school children in Geoje island was investigated by using adhesive cellotape anal swap method, in September, 2002. Total egg positive rates of E. vermicularis were 9.8% (74/754) and those of male and female were 10.8% and 8.7%, respectively. Among three schools examined, Myeongsa primary school showed the highest egg positive rate (12.6%) followed by Yeoncho [9.8% (26/266)] and Geoje [9.1% (35/385)]. As for the age groups, the 2nd grade had the highest egg positive rate (15.3%), whereas the 5th grade showed the lowest egg positive rate (2.6%). The above result led us to confirm that the egg positive rates of E. vermicularis in primary school children in Geoje island were not significantly different from the those in the whole country including urban and rural areas, showing more than 10%.

Potential remedy against Echinococcus multilocularis in wild red foxes using baits with anthelmintic distributed around fox breeding dens in Hokkaido, Japan.

The effect of bait-delivered anthelmintic to reduce the prevalence of Echinococcus multilocularis in wild red foxes was evaluated in Koshimizu, in the eastern part of Hokkaido, Japan. The study area (200 km2) was divided into baited and non-baited sections. The anthelmintic baits were distributed around fox den sites in the baited section every month for 13 months. After 1 year of the anthelmintic bait distribution, the prevalence of E. multilocularis in foxes, evaluated either by the parasite egg examination (from 27.1 to 5.6%) or coproantigen ELISA (from 59.6 to 29.7%), decreased in the baited section contrasting to that in the non-baited section (parasite egg: from 18.8 to 24.2%; ELISA: from 41.9 to 45.8%). The prevalence of E. multilocularis in grey red-backed vole Clethrionomys rufocanus, caught around fox dens, born after bait distribution also decreased and was significantly lower than that in non-baited section. However, within the study periods, the coproantigen-positive rate in fox faeces sporadically increased, while egg-positive rate constantly decreased. Since coproantigen ELISA can detect pre-patent infection, this observation indicates that reinfection pressure in the baited section was still high even after the 13 months of anthelmintic bait distribution. Therefore, the bait distribution longer than our study period is required for the efficient control of E. multilocularis in wild red fox population.

Infection status of Clonorchis sinensis in residents of Hamyang-gun, Gyeongsangnam-do, Korea.

Oriental liver fluke (Clonorchis sinensis) infection was surveyed among residents of Hamyang-gun, Gyeongsangnam-do, Korea during the period of January 2001 to March 2002. Total 1,041 stool samples were collected from residents who visited Public Health Center and its branches in Hamyang-gun and examined using formalin-ether sedimentation method. The overall egg positive rate was 16%, male showing higher positive rate (21%) than female (10%). The age group of 30 to 50 years had the highest egg positive rate of C. sinensis from 20% to 22%. The positive examinees were treated with praziquantel and educated individually to prevent reinfection. Egg positive rate in this area was decreased when compared with results recorded in the past, however, still remained more than 10%. This study suggests that periodic examination, treatment as well as education of residents should be continued and systematized.

Epidemiological study of clonorchiasis and metagonimiasis along the Geum-gang (River) in Okcheon-gun (County), Korea

The endemic status of clonorchiasis and metagonimiasis along the Geum-gang (River) in Okcheon-gun (County) in Korea was examined. From February to December 2000, stools of total 1,081 inhabitants living in 5 villages were examined. Each stool specimen was examined by both the cellophane thick smear method and the formalin-ether sedimentation technique. Egg-positive cases were further analyzed by Stoll's egg-counting technique, and praziquantel was administered to positive cases. The egg-positive rates for Clonorchis sinensis and Metagonimus species were 9.3% and 5.5%, respectively, and the double infection rate was 3.5%. The numbers of eggs per gram (EPG) of feces of C. sinensis and Metagonimus sp. were 918 +/- 1,463 and 711 +/- 947, respectively. The egg-positive rates for C. sinensis and Metagonimus sp. in the riverside area were 14.2% and 8.4%, respectively, which were significantly higher than those of the inland area (3.2% and 1.7%, respectively). The egg-positive rates of C. sinensis and Metagonimus sp. in males (16.7% and 10.0%) were significantly higher than those of females (3.5% and 1.8%). However, there were no significant differences of EPG values between localities and sexes. The prevalence of clonorchiasis and metagonimiasis in this survey was significantly lower than that in the previous reports. However, there is still a high prevalence of infection with C. sinensis and Metagonimus sp. in this region, especially in the riverside area.

Infection rates of Enterobius vermicularis and Clonorchis sinensis of primary school children in Hamyang-gun, Gyeongsangnam-do (province), Korea.

The egg positive rate of Enterobius vermicularis and Clonorchis sinensis of school children in the rural area was studied in Hamyang-gun, Gyeongsangnam-do in Korea. Cellotape anal swab and formalin ether concentration methods were performed one time to 720 primary school children. The total egg positive rate of E. vermicularis was 12.6% in two schools (Baekjeon and Wiseong). In the Baekjeon and Wiseong primary school, the egg positive rate of E. vermicularis was 4.6% and 13.4%, respectively. Pinworm egg positive rate was 17.6% in the lower grades (1st, 2nd and 3rd), and 7.7% in higher grades (4th, 5th and 6th). The total egg positive rate of male and female was 12.6% and 12.7%, respectively. The egg positive rate of C. sinensis of Baekjeon and Wiseong primary school was 1.5% and 0.46%, respectively. The total egg positive rate of C. sinesis was 0.56%. This survey showed that continuous education and chemotherapy is necessary to treat and prevent reinfection of E. vermicularis. In the case of C. sinensis, health education for school children is recommended to prevent potential infection of adolescents.

A review of Gymnophalloides seoi (Digenea: Gymnophallidae) and human infections in the Republic of Korea.

Studies on Gymnophalloides seoi (Digenea: Gymnophallidae) and human infections are briefly reviewed. This minute intestinal fluke was first discovered from a Korean woman suffering from acute pancreatitis and gastrointestinal troubles. It was described as a new species by Lee, Chai and Hong in 1993. The southwestern coastal village where the patient resided was found to be a highly endemic area, and additional endemic areas have been identified. The parasite is very small, 0.33-0.50 mm long and 0.23-0.33 mm wide, and characterized by the presence of a ventral pit. The first intermediate host remains unknown, but the second intermediate host has been found to be the oyster Crassostrea gigas. Man and the Palearctic oystercatcher Haematopus ostralegus have been shown to be natural definitive hosts, and wading birds including the Kentish plover Charadrius alexandrinus are highly susceptible to experimental infection. Gerbils, hamsters, cats, and several strains of mice were also susceptible laboratory hosts. In experimentally infected mice, the parasites inhabit the small intestine, pinching and sucking the root of villi with their large oral suckers, but they did not invade beyond the mucosa in immunocompetent mice. However, they were found to invade the submucosa in immunosuppressed mice. Human G. seoi infections have been found in at least 25 localities; 23 islands on the Yellow Sea or the South Sea, and 2 western coastal villages. The highest prevalence was found in a village on Aphaedo, Shinan-gun (49% egg positive rate); other areas showed 0.8-25.3% prevalence. Infected people complained of variable degrees of gastrointestinal troubles and indigestion. The infection can be diagnosed by recovery of eggs in the feces; however, an expert is needed to identify the eggs. Praziquantel, 10 mg/kg in single dose, is effective for treatment of human infections. Eating raw oysters in endemic areas should be avoided.

Enterobius vermicularis egg positive rates in primary school children in Gangwon-do (province), Korea.

A survey of the infection rate of Enterobius vermicularis among students in 4 primary schools located in Gangwon-do (Province) was done from May to June 2001. Among the 398 examinees, 39 (9.8%) were infected with E. vermicularis demonstrated by the adhesive cellotape anal swab method. The infection rates ranged from 8.3% to 11.8% among the four schools. The infection rate of males and females was 10.7% and 7.7% respectively. The first grade students showed the highest infection rate, 28.7%. The confirmed cases were treated with albendazole three times at an interval of 15 days. We were able to confirm that E. vermicularis infection is still prevalent among students in Gangwon-do, Korea.

Enterobius vermicularis egg positive rate in a primary school in Chungchongnam-do (province) in Korea.

The egg positive rate of Enterobius vermicularis was investigated among students of a primary school and a kindergarten located in the rural area of Tangjin-gun, Chungchongnam-do in December, 1998. Of the 189 examinees, 28 (14.8%) were found to be infected with E. vermicularis by the adhesive cellotape anal swab method. The infection rates ranged from 4.2% to 26.1% among school children, and the highest rate was observed in children attending kindergarten. Three months after treatment with albendazole, four (14.3%) out of 28 infected children still remained infected with E. vermicularis. Through this survey, we were able to determine that E. vermicularis infection is still prevalent among children in rural areas of Korea.

Persistent endemicity of Gymnophalloides seoi infection in a southwestern coastal village of Korea with special reference to its egg laying capacity in the human host.

Follow-up studies have been conducted every three years on the endemicity of Gymnophalloides seoi infection in a small coastal village of Chollanam-do (Province), Korea, since it was first known as an endemic area in 1994. Special attention was given to its egg laying capacity in the human host. In fecal examinations, the overall helminth egg and/or cyst positive rate was 78.7% (74/94) in 1997 and 76.6% (82/107) in 2000. Among them G. seoi eggs showed the highest rate; 71.3% (67/94) in 1997 and 72.0% (77/107) in 2000. The average number of eggs per gram of feces (EPG) was 1,015 in 1997, while a reduced rate of 353 was observed in 2000. In 1997, total of 320,677 adult flukes of G. seoi (av. 10,344/person, 94-69,125 in range) were collected from the diarrheic stools of 31 treated patients. The EPG/worm obtained from 21 cases ranged from 0.04 to 0.77 (av. 0.23), suggesting density-dependent constraints on the worm fecundity. The relationship between the worm burden (X) and EPG/worm (Y) can be expressed as Y = 0.42.e-1.2 chi (r = 0.49). The results showed that G. seoi infection is persistently endemic in this village.

Enterobius vermicularis egg positive rate of pre-school children in Chunchon, Korea (1999).

Pre-school children were examined for the presence of Enterobius vermicularis egg by perianal swab method. We visited 67 nurseries and 25 kindergartens between January, 1999 and April, 1999 in Chunchon, Korea. Of the 4,711 children examined, 434 (9.2%) were found to be positive for E. vermicularis egg. The egg positive rates of boys and girls were 10.1% and 8.1%, respectively. The rates were 7.8% in kindergartens and 9.7% in nurseries. Positive rate of 50 institutions was less than 10%. Rate in 35 institutions was from 10% to less than 20%. Rate in 7 institutions was equal to or over 20%. Out of 1,113 children examined twice, 28 (2.5%) children were positive consecutively, 53 (4.8%) were positive with negative conversion, 47 (4.2%) were negative with positive conversion, and 985 (88.5%) were consecutively negative. It means that in the low endemic area of enterobiasis with around 10% positive rate, the two consecutive examinations may increase the egg detection rate of 4.2-4.8%. The small number of consecutive egg positive children also suggests that the worm burden of the positive children might be low. Since the egg positive rate of that age group in this City increased from 1.85% (1997), and 3.0% (1998), the more intensive regular control should be executed.

High endemicity of Metagonimus yokogawai infection among residents of Samchok-shi, Kangwon-do.

A small-scale epidemiological survey was undertaken during 1997-1998 on the residents along the Osib-chon (Stream), Samchok-shi (City), Kangwon-do (Province), to evaluate the status of Metagonimus yokogawai infection. A total of 165 fecal samples was collected and examined by cellophane thick smear and formalin-ether sedimentation techniques. The egg positive rate of M. yokogawai was 29.7%, showing a remarkable difference between males (46.6%) and females (16.3%). To obtain the adult flukes of M. yokogawai, 11 egg positive persons were treated with praziquantel and purged with magnesium sulfate. A total of 242,119 adult flukes (average 22,010 per person, 367-119,650 in range) was collected from diarrheic stools, all of which were identified as M. yokogawai. The results show that M. yokogawai is still highly endemic in this area.

Epidemiologic study of the relationship between schistosomiasis due to Schistosoma japonicum and liver cancer/cirrhosis.

In Yamanashi Prefecture, one of the former areas in Japan endemic for Schistosoma japonicum, there have been no cases of schistosomiasis since 1978. We attempted to find out in this study whether there was still a chronic effect of schistosomiasis, e.g., liver cancer or liver cirrhosis present in this region. The subjects studied were the population in Yamanashi Prefecture from 1973 through 1992. We divided the population into residents in an area endemic for schistosomiasis and those in a nonendemic area. We calculated the standardized mortality ratios (SMRs) for liver cancer and liver cirrhosis in both areas. The schistosome egg-positive rate of liver cancer and liver cirrhosis specimens from the patients in these two endemic areas was also calculated. Male SMRs for liver cancer in the endemic area were 188.5% in 1985 and 188.0% in 1990. Even today, many years after the last case of schistosomiasis, schistosome eggs can be found in the livers of deceased liver cancer and cirrhosis patients. The chronic effect of S. japonicum could contribute to the current high mortality rate for liver cancer in the endemic area, although we need to consider the other etiologic factors of liver cancer, e.g., hepatitis B virus, hepatitis C virus, and alcohol intake.

Two endemic foci of heterophyids and other intestinal fluke infections in southern and western coastal areas in Korea.

Two endemic foci of heterophyid infections were discovered in coastal villages of Puan-gun, Chollabuk-do, and Sachon-gun. Kyongsangnam-do, Korea. Fecal examinations 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-gun, 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 was 18.8%, followed by Clonorchis sinensis (12.3%), and other parasites (0.7-5.0%). Twenth-two (Puan-gun) and six (Sachon-gun) heterophyid egg positive cases were treated with 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: Pygidiopsis summa, Stellantchasmus falcalus. Metagonimus yokogawai, M. miyatai, Stictodora fuscata. Heterophyopsis continua, Acanthoparyphium kurogamo, and Gymnophalloides seoi. In Sachon-gun, M. yokogawai (3,007 specimens), H. nocens (120), and S. falcatus (46) were collected from 5 of 6 treated patients, and H. continua and S. lari each from one patient. The present study revealed that heterophyid flukes, especially H. nocens and M. yokogawai, are prevalent in the southern and western coastal areas of Korea where fresh and/or brackish water fishes are popularly eaten raw.

A new endemic focus of Heterophyes nocens, Pygidiopsis summa, and other intestinal flukes in a coastal area of Muan-gun, Chollanam-do.

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.

Egg positive rates of Clonorchis sinensis and intestinal helminths among residents in Kagye-ri, Saengbiryang-myon, Sanchong-gun, Kyongsangnam-do.

Stools of the residents in a village in Saengbiryang-myon, Sanchong-gun, Kyongsangnam-do were examined for the eggs of intestinal helminths. In 1987, infection rate of 76 residents by Clonorchis sinensis was 80.3% with mean eggs per gram of feces (EPG) 27,781. C. sinensis-infected persons were treated once with praziquantel 60 mg/kg, q.i.d. Seventeen persons (22.4%) infected by Metagonimus yokogawai was coinfected with C. sinensis. In 1993, C. sinensis egg positive rate was 48.4% with mean EPG 5,929. Reinfection rate of follow-up cases by C. sinensis was 55.2% during 5 years and 5 months. Infection rate by M. yokogawai was 3.2%. This village was an endemic focus of clonorchiasis occurring reinfection high.

Second report on intestinal parasites among the patients of Seoul Paik Hospital (1984-1992)

The results of fecal examination for helminth eggs and protozoan cysts in Seoul Paik Hospital during 1984-1992 are reported. Fecal specimens of a total of 52,552 out- or inpatients were examined by formalin-ether sedimentation and/or direct smear method. The overall egg positive rate of helminths was 6.5% and the cyst positive rate of protozoa 2.5%. The egg positive rate (number of positive cases) for each species of helminth was; Clonorchis sinensis 3.2% (1,667), Trichuris trichiura 2.0% (1,089), Metagonimus yokogawai 1.2% (613), Ascaris lumbricoides 0.2% (100), Trichostrongylus orientalis 0.1% (34), Taenia spp. 0.05% (28), Hymenolepis nana 0.03% (18), hookworms 0.03% (17), Paragonimus westermani 0.02% (12), Echinostoma spp. 0.03% (12), Enterobius vermicularis 0.02% (10), Strongyloides stercoralis (larvae) 0.01% (6), and Diphyllobothrium latum 0.004% (2). The cyst positive rate (number of positive cases) for each protozoan was; Entamoeba coli 1.1% (588), Endolimax nana 0.8% (402), Giardia lamblia 0.3% (173), Entamoeba histolytica 0.3% (164), and Trichomonas hominis (trophozoites) 0.004% (2). Viewing from the data of 9 years, it was evident that the prevalence of soil-transmitted helminths such as A. lumbricoides and T. trichiura has been decreasing remarkably, while that of snail-transmitted helminths such as C. sinensis and intestinal protozoans has not.

The first discovery of an endemic focus of Heterophyes nocens (Heterophyidae) infection in Korea.

A highly endemic focus of human infection with Heterophyes nocens (Heterophyidae) was discovered from a small coastal village of Shinan-gun, Chollanam-do, for the first time in Korea. Fecal examinations by cellophane thick smear and formalin-ether sedimentation techniques revealed 42.9% heterophyid egg positive rate out of 98 inhabitants examined. It was difficult to confirm the species of heterophyids only by eggs. In order to collect the adult flukes, the egg positive cases were treated with 10 mg/kg single dose of praziquantel and purged with magnesium sulfate, and the adult worms were collected from the diarrheic stools. From each of 18 cooperative patients 1 to 1,124 (total 4,730) H. nocens worms were recovered, together with a few to large numbers of heterophyids (Pygidiopsis summa, Stictodora fuscatum) and/or gymnophallids (Gymnophalloides seoi). It is speculated that H. nocens might be widely distributed along the southwestern coastal areas where the brackish water fish such as the mullets or gobies are popularly eaten raw.

Intestinal flukes of genus Metagonimus and their second intermediate hosts in Kangwon-do

This study investigate the epidemiological feature of Metagonimus infection in Kangwon-do (province). The average infection rate of the surveyed inhabitants was 7.8% (83 positives out of 1, 067 examinees) by stool examination; male, 11.4% and female, 3.2%, respectively. The egg positive rate in residents in the Som river area was 7.3%, that of the Chuchon river area 6.3%, the Pyongchang river area 12.8%, the Tong river area 3.8%, the Hongchon river area 9.8%, and the Ohsip stream area of Samchok 8.0%, respectively. The average metacercarial infection rate of genus Metagonimus in the fish was 81.0% (256 positives out of 318 fish). The infected fishes were Zacco platypus, Zacco temmincki, Opsariichthys bidens, Squalidis sp., Carassius carassius, etc. in western Kangwon-do Meanwhile, in the Ohsip stream area of Samchok-gun, eastern costal Kangwon-do, the infected fish were Plecoglossus altivelis and Tribolodon hakonensis. The rats and dogs are infected with the metcercariae obtained from Zacco platypus and Opsariichthys bidens, adult worms collected were Miyata type of Metagonimus with some M. takahashii. When infected with metacercariae from Plecoglossus altivelis, Metagonimus yokogawai was only found. M. yokogawai and Metagonimus Miyata type were found together in Tribolodon hakonensis in Ohsip stream area of Samchok, in the eastern Kangwon-do. The intestinal flukes of genus Metagonimus in western Kangwon-do were Miyata type of Metagonimus and M. takahashii, transmitting mainly by Zacco platypus and Opsariichthys bidens as a source of infection. In the eastern part of Kangwon province (Ohsip stream area of Samchok), M. yokogawai was mainly distributed by P. altivelis and T. hakonesis, but some T. hakonensis harbored the metacercariae of Miyata type of Metagonimus with those of M. yokogawai.

Current status and the changing pattern of the prevalence of clonorchiasis in the inhabitants in Sanchong-gun, Kyongsangnam-do, Korea

This study was conducted to evaluate the current endemicity and the transition mode of the Clonorchis infection in Sanchong-gun Kyongsangnam-do. The areas of investigation, villages and schools surveyed, method and techniques used in this study were the same as in 1984. The egg positive rate of clonorchiasis in the general population of Sanchong-gun was 37.6% out of 837 examined persons. In the schoolchildren, the rate was 9.7% out of 145 persons examined. In the intensity of the infection among the cases, the mean EPG (Egg per gram of feces) in the inhabitants and schoolchildren were 3,310 (male 4,221, female 1,978) and 711 (male 620, female 833), respectively. Of the inhabitants with clonorchiasis, the cases of light infection (EPG < 1,000) and moderate infection (1,000 < EPG < 10,000) were 93.9%. The proportion with experience of eating raw freshwater-fish was 90.5% among the infecteds. Out of 138 inhabitants examined in both 1984 and 1992, the number of the positives by both examinations was 31 (22.5%), positive to negative conversion was 35 (25.4%), negative to positive conversion was 22 (15.9%). The present results reveal that there are no changes of the egg positive rate of clonorchiasis among inhabitants in Sanchong and the eating habit of raw freshwater-fish persists there. In this community, the eating habit is the most important problem to be solved for control of this endemic disease.