• Parasites, Hosts and Diseases
• /
• v.58 no.5
• /
• pp.527-535
• /
• 2020

To clarify the reinfection profile associated with risk factors of opisthorchiasis, we conducted an epidemiological study on the chemotherapeutic effects on reinfection with O. viverrini in the endemic areas of Northeastern Thailand for 3 years. A total of 3,674 fecal samples were collected from participants in villages of 5 provinces. They were examined microscopically using a modified technique of formalin ethyl-acetate concentration. Egg-positive residents were reexamined year (2018) by year (2019) after treatment with a single dose (40 mg/kg) of praziquantel. Health education was provided to the participants yearly. The egg-positive rate of O. viverrini was 14.3%, and was highest (22.2%) in the 20-30 year-old group in 2017. The egg positive rate was 15.3% in dogs and 11.4% cats. Human reinfection rate was 15.5% and 6.3% in next 2 years, and was highest (23.2%) among the fishermen. Relative risk factors of reinfection were significantly higher for males, over 40-year-old age, or working as fishermen or farmers, and eating uncooked fish within the preceding year. A significant difference resulting from a health education program was observed in the third year. Therefore, health education and sustainable surveillance for opisthorchiasis should be maintained to decrease the risk of reinfection.

• Clinical and Experimental Pediatrics
• /
• v.49 no.3
• /
• pp.268-272
• /
• 2006

Purpose : The reinfection rate of H. pylori reported before $^{13}C$-urea breath test($^{13}C$-UBT) era was higher than that of the post $^{13}C$-UBT era. Children are usually reluctant to receive invasive endoscopic evaluation for the reinfection of H. pylori, particularly when they are asymptomatic. The aim of the study is to discover the reinfection rate by different diagnostic tests, and to find out what causes the difference. Methods : Children confirmed to be eradicated from H. pylori were included in the study. Reinfection was evaluated by endoscopic biopsy based tests(n=34, mean age $11.5{\pm}3.7$ years) and/or a $^{13}C$-UBT(n=38, mean age $10.0{\pm}3.6$ years) at the time of 18 months after eradication. At first visit, H. pylori infection had been diagnosed by positive results from a rapid urease test, Giemsa stain and Warthin-Starry stain and/or a positive culture. Eradication was defined as negative results from all above tests 1-3 months after eradication therapy. Results : Reinfection rate by endoscopic biopsy based tests was 35.3 percent(12/34). All patients had abdominal symptoms(P=0.000). Reinfection rate was 13.2 percent(5/38) by a $^{13}C$-UBT. Reinfection rate was higher in children with abdominal symptoms(P=0.008). There was no evidence that reinfection rate depended on the sex(P=0.694), age(P=0.827), diseases(peptic ulcers vs gastritis, P=0.730) and eradication regimen(P=0.087). Conclusion : Helocibacter pylori reinfection rate in Korean children was 13.2 percent per 18 months by a non-invasive test or $^{13}C$-UBT. Accurate determinations of the reinfection rate in children is affected by the compliance of the diagnostic tests. Non-invasive tests should be considered to investigate the reinfection rate in children.

• Parasites, Hosts and Diseases
• /
• v.42 no.1
• /
• pp.19-26
• /
• 2004

We investigated the induction of resistance to Clonorchis sinensis infection by prior infection in rat and hamster models. Animals were challenged with C. sinensis metacercariae, then treated with praziquantel and reinfected. Worm recovery rate in reinfected animals was used to estimate resistance to reinfection. The determined resistance rates to reinfection in rats and hamsters were 97.7% and 10.3%, respectively. In rats, cure from the primary infection of C. sinensis increased resistant to reinfection, and the greatert the worm burden and the longer the duration of primary infection, the higher was the resistance rate. For primary infection doses of 10, 40 and 100 metacercariae per rat, the resistance rates were 87.4%, 93.8% and 98.4%, respectively. The resistance rates in rats after 2 or 8-week primary infection were 78.7% and 95.3%, respectively. All worms recovered from reinfected rats were immature. When cured rats were administered with methylprednisolone, resistance to reinfection became impaired. These findings indicate that rats develop a high degree of resistance to reinfection by C. sinensis after cure. The growths and maturations of reinfected worms were also impaired.

• Parasites, Hosts and Diseases
• /
• v.21 no.2
• /
• pp.142-149
• /
• 1983

Epidemiological studies on the reinfetion pattern of Ascaris lumbricoides were undertaken by means of blanket mass chemotherapy and worm collection in a rural village in Korea, during 1977~1980. The study objectives were to determine the age (sex)-specific reinfection rate during 2, 4, 6 and 12 months through repeated mass chemotherapy with pyrantel pamoate, and to observe the familial aggregation tendency of the reinfected cases. The results obtained are as follows: 1. The age (sex)-reinfection curve revealed that the reinfection rate is much higher in younger individuals than in olders in all of 4 kinds of interval chemotherapy groups. The highest reinfection rate and the highest burden of reinfected worms were observed in preschool children, followed by primary school students. Such fluctuation in the age-specific reinfection rates was more pronounced in males than in females. 2. There was noted a significant tendency of familial aggregation among the reinfected cases. It is suggested that reinfection occurs never randomly but preferably to the members of certain household families. From these reinfection analyses, it is inferred that the principal mode of A. lumbricoides transmiSSIOn in the surveyed rural area is likely to be of 'dooryard type', in which case children and certain family members are more preferably reinfected. It is also suggested that the preschool children should be included in the primary targets of mass control programme.

• Journal of agricultural medicine and community health
• /
• v.28 no.1
• /
• pp.79-92
• /
• 2003

Objectives: To investigate the reinfection rate of Helicobacter pylori and the factors related to reinfection of H. pylori, 86 persons were examined in April 2000 after 1 year follow-up period and 77 persons were examined in October 2001 after two and a half-year follow-up period in Gyeongju-si, Gyeongsangbuk-do, Korea. Methods: The subjects were confirmed as H. pylori negative by urea breath test(UBT), and asked to answer the questionnaire regarding demographic characteristics, dyspepsia symptoms, health-related behaviors and family history. Results: The reinfection rate on the first year of the eradication of H. pylori was 15.6%, when the 77 subjects have finished follow-up observation for one year. In the urea breath test performed after two and a half year, 13 out of 77 were positive, with the reinfection rate of 16.9%. Age, sex, socio-economical status, educational level and family history were not associated with the reinfection, while there was significant association between the reinfection and postprandial fullness and epigastric bloating in subjective dyspepsia that the subjects who were determined to be negative in the urea breath test for the following year. The treatment compliance and drinking were significant variables in univariate analysis. Meanwhile, the cases in which the dyspepsia symptom scores for the recent year were 2 to 3 points served as the only statistically significant variable in multiple logistic regression analysis, with the odds ratio of 4.5. The cases in which salt intake during meals was exceeded were 8.7 in the odds ratio, but statistically insignificant. Conclusions: Conclusively, the first-year reinfection rate was 15.6%, and the second-year reinfection rate was 16.9%. Thecomplaints of subjective dyspeptic symptoms and the treatment compliance, as the basis for predicting the H. pylori reinfection in communities, can be used as the basis to screen the subjects for follow-up examination to find out H. pylori infection.

• Asian Pacific Journal of Cancer Prevention
• /
• v.17 no.2
• /
• pp.857-862
• /
• 2016

Background: The prevalence of infection by the liver fluke, Opisthorchis viverrini (O. viverrini), has remained high in Northeast Thailand where it is a major risk factor for the eventual development of cholangiocarcinoma (CCA). The infection is acquired by the consumption of dishes containing unsafely prepared freshwater fish, a dietary tradition which has proved resistant to change. Since many people are aware that dosing with praziquantel (PZQ) is a successful treatment for an episode of the infection, there is a risk that, to avoid the long term consequences, they will engage in a cycle of infection, dosing and reinfection. Objectives: There is a dearth of studies of reinfection by O. viverrini, and the aims of this study were to assess re-infection rates in a typical province of Northeastern Thailand where O. viverrini infection is likely and to investigate factors associated with reinfection. Materials and Methods: A total of infected 607 villagers were treated with PZQ, and those found to be no longer infected were followed up at six-monthly intervals over 12 months. Results: At the end of this period data on 457 subjects were available for analysis using descriptive statistics and logistic regression, and 50 were found to have become reinfected, giving a cumulative reinfection rate of 10.9%. The results of a multiple logistic regression analysis showed that the only factor found to be associated with reinfection was past use of PZQ. Conclusions: Recommendations are made for future larger scale and better designed reinfection studies in the light of limitations of the current study. Further efforts are needed to discourage people from eating fish dishes likely to contain viable metacariae.

• Parasites, Hosts and Diseases
• /
• v.32 no.4
• /
• pp.271-274
• /
• 1994

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 sinenis 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 Metosonimw yokogcwoi was coinfected with C. sinensis. In 1993. C. sirensis 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 MW. yokogauwai was 3.2%. This village was an endemic focus of clonorchiasis occurring reinfection high.

• Parasites, Hosts and Diseases
• /
• v.21 no.2
• /
• pp.135-141
• /
• 1983

The epidemiological relationship between the current prevalence and monthly reinfection rate of Ascaris lumbricoides was observed in rural communities in Korea by means of blanket mass chemotherapy and worm collection for measurement of the prevalence and reinfection rates. During the period from 1975 to 1980, a total of 4,466 inhabitants in 10 different localities were treated with 10 mg/kg of pyrantel pamoate and 2 days' whole stools were collected from 2,547 inhabitants. The stools were examined for the presence of expelled adult and/or young worms, which represent the prevalence and reinfection rates for past 2 months respectively. After then, the obtained rates were correlated each other applying the timeprevalence curve proposed by Hayashi. It was observed that the prevalence (overall worm positive rate) and worm burden per individual ranged by areas from 13. 6 to 72. 3% and 1.4~10. 2 respectively. The calculated monthly reinfection rates (X) (from young worm positive rates) according to areas were in the range, 2.6~16.2%, and clearly correlated with the current prevalence (Y) under the equation, $Y=1-(l-X)^{7.2}$ where 7.2 is time in month. The equation means that after one time mass chemotherapy the period needed to attain equilibrium of prevalence again would be about 7~8 months. And it is inferred that the majority of reinfected worms in human host turn over every 7~8 months.

• Parasites, Hosts and Diseases
• /
• v.33 no.1
• /
• pp.37-44
• /
• 1995

Neodiplostomum seoulensis, one of the human intestinal trematodes , was reinfected to albino rats, and worm recovery rates, histopathology and activity changes of the intestinal brush border membrane bound enzymes were observed. The experimental groups were three: uninfected, primary infection and reinfection. The worm recovery rate in the reinfection group was much lower than in the primary infection group 14 days after infection. The duodenal histopathology showed villous atrophy during the first and second week in the primary infection group. In the reinfection group, however. villous changes occurred as early as 3 days after the infection, and the lesion was found healed 7 days after infection. The activities of alkaline phosphatase and sucrase in the duodenum of primary infection rats decreased nearly half of the controls 2 weeks after infection, whereas the activities were unchanged in the reinfection group. However, no changes in the activities were observed in the proximal jejunum between the experimental groups. These findings suggested that a secondary infection of N. seouLensis in rats should make less damage on the intestinal mucosa than a primary infection. Key words: Neoniplostomum seoulensis, albino rats, reinfection, worm recovery, histopathology, brush border membrane bound enxyines.

• Journal of agricultural medicine and community health
• /
• v.24 no.2
• /
• pp.225-232
• /
• 1999

A survey of an endemic locality at Songjung Ri, Ogok Myun, Goksung County, South Cholla Province for the prevalence of Clonorchis sinensis and Metagonimus yokogawai was primarily done on 53 residence before medication using formalin-ether concentration method of stool examination. After praziquantel medication of all the clonorchiasis patients, 64 humans consisting 82.1% of total inhibitants and including 84.9% of primarily surveyed residents were secondly surveyed after 2-year post-treatment to evaluate the prevalence and reinfection. The prevalence of clonorchiasis was decreased from 35.8% before medication to 10.9% after medication(P<0.01), indicating this disease was not satisfactorily controlled although the rate was significantly lowered. The prevalence of metagonimiasis was dropped from 17.0% to 6.3% on post-treatment. In clonorchiasis cases, sex ratio showed no difference in both pre- and post-treatment, and mean age was the sixties after medication from the forties and fifties before medication, suggesting more aged people of both sexes were infected with this fluke. The reinfection of clonorchiasis and metagonimiasis following 2-year post-treatment was 15.8% and 25.0%, respectively. The proportion of reinfection among the egg positive cases was 50.0% in clonorchiasis and 100% in metagonimiasis. These findings mean that a high fraction of clonorchiasis and metagonimiasis was reinfected with these trematodes. In conclusion, to eradicate the C. sinensis and M. yokogawai in an endemic area, it should be preceded to control the reinfection of these parasites.