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Objective To determine the ability of oysters to trap and maintain viable Cryptosporidium oocysts, and the feasibility of Cryptosporidium multiplication in oysters' organs. Methods Seventy oysters were raised in experimentally seeded natural seawater for up to 3 months, with weekly oocysts inoculations. Cryptosporidium oocysts, viable and non-viable, as well as other stages were detected using two immunofluorescence vital staining techniques (Sporo-Glo and Merifluor
ABSTRACT
OBJECTIVE@#To determine the ability of oysters to trap and maintain viable Cryptosporidium oocysts, and the feasibility of Cryptosporidium multiplication in oysters' organs.@*METHODS@#Seventy oysters were raised in experimentally seeded natural seawater for up to 3 months, with weekly oocysts inoculations. Cryptosporidium oocysts, viable and non-viable, as well as other stages were detected using two immunofluorescence vital staining techniques (Sporo-Glo and Merifluor(®)) with confocal microscopy. Viability rate at various times after inoculations were calculated.@*RESULTS@#Cryptosporidium oocysts were found most concentrated in oysters' digestive organs than in gill and water inside the oysters. Oocysts numbers were 857.33 at 24 h after inoculation and strikingly decreased to 243.00 and 126.67 oocysts at 72 h and 7 days, respectively. The oocysts in oyster were also less viable over time; 70%, 60% and 30% viable at 24 h, 72 h and 7 days after inoculation, respectively. At 77 days, the number of oocysts was very low and none was found at 84 days onwards. Although some oocysts were ruptured with released sporozoites, there was no evidence throughout the study of sporozoites multiplication to indicate that oyster is a biological host. Despite the significant reduction in oocysts number after 7 days of inoculation, the remained viable oocysts can still cause cryptosporidiosis.@*CONCLUSION@#The findings confirm that Cryptosporidium parvum does not multiply in oyster, and is therefore not a biological host. Nevertheless, the results suggest that oyster can be an effective transmission vehicle for Cryptosporidium oocysts, especially within 24-72 h of contamination, with viable oocysts present at up to 7 days post infection. Unless consuming well-cooked oyster dishes, eating raw oyster remains a public health concern and at least 3 days of depuration in clean sea water prior to consumption is recommended.
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The majority of <i>Giardia</i> infections are transmitted by the fecal-oral route and cause giardiasis. Children who live in crowded conditions or low socio-economic areas are the risk group for <i>Giardia</i> infection. Interestingly, most of them are asymptomatic or only mildly infected and can shed the <i>Giardia</i> cysts in the environment. Thus, the diagnosis of <i>Giardia</i> infection in asymptomatic or mild infection plays an important role in achieving control of <i>Giardia duodenalis</i> transmission. The objective of this study was to examine parasitic infections using microscopy and to develop a real-time PCR method for detection of <i>Giardia</i> infection in the stool samples of children living on the Thai-Myanmar border. Both species-specific primers and fluorescent labeled <i>G. duodenalis</i> probe were designed using small-subunit ribosomal RNA (<i>ssrRNA</i>). The results showed that 10 (7.69%) and 40 (30.77%) of 130 stool samples were positive for <i>G. duodenalis</i> by microscopy and real-time PCR respectively. Only 3 out of 9 liquid stools revealed <i>G. duodenalis</i> positive using microscopy, but all of them were <i>G. duodenalis</i>-positive using real-time PCR. The detection limit of real-time PCR for <i>G. duodenalis</i> was 0.1 pg/25 µl reaction. It can detect both mild and asymptomatic <i>Giardia</i> infections in children living on the Thai-Myanmar border.
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Background: Enterobius vermicularis (Nematoda: Oxyuroidae) is a nematode worm, parasitic in the intestine of humans, and especially infects school children in most parts of the world. Infection occurs after ingesting drinks or food contaminated by the pinworm eggs. Samut Prakan province is located south-east of the Bangkok metropolitan area.Objective: To analyze enterobiasis infections among Thai school children in Samut Prakan province of Thailand, using a geographic information system.Methods: A total of 1,255 school children from eleven primary schools in the Samut Prakan province were drawn by stratified random sampling and tested for the presence of E. vermicularis eggs from December 2000 to March2001.Results: Diagnostic results and socioeconomic information about students and their families were integrated into a Geographic Information System (GIS) and spatially interpreted, using SavGIS programmes. Other needed environmental data, extracted from satellite images using remote sensing, was used for further analysis. Laboratory analysis revealed a 17.5% overall prevalence with 10.5% of the children having a low infection rate, 2.6% a moderate, and 4.4% a heavy infection rate. The prevalence of E. vermicularis showed geographical heterogeneity with the lowest prevalence in the provincial administrative center. Parents’ occupation was significantly correlated with the presence of infection.Conclusion: Spatial analysis can help to identify patterns of high risk for enterobiasis otherwise called oxyuriasis.
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Background: Helminth infection is a worldwide problem and prevalent in low income areas. The costs for prevention, treatment and eradication have so far frustrated budgets of global public health systems. Objective: The present study was to determine the epidemiologic characteristics of worm infections in two “Long Neck” hill tribe villages in Mae Hong Son Province of Thailand. We evaluated how epidemiologic characteristics of infection could be used for control and eradication in a cost effective manner. Materials and methods: In January 2002, investigators visited two “long neck” villages. The team explained the purpose of the study and how to collect specimens in the Karen language. The population in the two villages was 300 in 2002. Results: Stool samples were collected from 133 subjects (age range: 1 to 67 years old), 54.1% (72/133) of the subjects were female. The parasites rate was 11% (15/133). Parasites included 8 cases of Trichuris trichiura and 6 cases of hookworm. Conclusion: Most infections (69%) occurred in the 21-30 age-group. By using the present data, the Provincial Health Office in Mae Hong Son conducted mass treatment and was able to target high risk individuals.