In January 2005, a survey of intestinal parasitic infections was performed in a primary school, central Thailand. Of 675 stool samples, Blastocystis was identified with a prevalence of 18.9%. Genetic characterization of Blastocystis showed subtype 1 (77.9%) and subtype 2 (22.1%). Study of the water supply in this school was performed to find the possible sources of Blastocystis. Blastocystis from one water sample was identified as subtype 1, which had a nucleotide sequence of small subunit (SSU) ribosomal RNA (rRNA) gene that was 100% identical to that of Blastocystis infected in schoolchildren. Our information supports the evidence of water-borne transmission in this population.

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Currently, the detection of human infection with Blastocystis hominis is usually based on the examination under a light microscope of faecal samples, either directly, as 'simple smears', or after some form of concentration. Whether short-term, in-vitro cultivation would increase the sensitivity of such detection remains a matter of controversy. Over 900 fresh stool specimens, from soldiers in the Royal Thai Army, were each checked for the parasite using three methods: simple smears; formalin-ethyl-acetate concentration; and cultivation in Jones' medium. Although 334 of the samples were found to be culture-positive, the parasites were only detected in 142 of the simple smears, and faecal concentration led to an even lower sensitivity (64 positive samples). In-vitro cultivation does seem worthwhile in the detection of B. hominis carriage in field studies.

A cross-sectional study was performed in February 2001 to evaluate the prevalence and risk factors of Blastocystis hominis infection in army personnel who resided in an army base in Chonburi, Thailand. A total of 904 army personnel were enrolled in this study. Short-term in vitro cultivation was used to detect B. hominis in stool samples. In this population, B. hominis was the parasite most frequently found, and was identified in 334 of 904 stool specimens (36.9%). A significant association between B. hominis infection and symptoms was identified that might emphasize the role of B. hominis as a human pathogen. After adjustment for potential confounders, significantly increased risk of being infection with B. hominis was associated with being a private, working in a specific unit, and consuming unboiled drinking water. Thus, waterborne transmission of B. hominis infection was indicated at this army base. However, other modes of transmission cannot be ruled out.

When in vitro cultivation was used as the 'gold standard' for the detection of Blastocystis hominis in stool specimens, simple smear and trichrome staining showed sensitivities of 16.7% and 40.2% and specificities of 94% and 80.4%, respectively. In vitro cultivation also enhanced PCR amplification for the detection of B. hominis in stool specimens. Our data show the usefulness of in vitro cultivation for the detection and molecular study of B. hominis in stool specimens.

We determined that 15.7% of pigs and 1.4% of humans in a pig farm community in central Thailand harbored Enterocytozoon bieneusi. Genotyping of E. bieneusi from pigs showed genotypes O, E, and H. However, only genotype A was found in human subjects. This indicates nonzoonotic transmission of E. bieneusi in this community.

Opisthorchis viverrini infection is one of the major public health problems in Thailand. Although information about transmission of this parasite to humans is well established, infections are still prevalent in the northern and northeastern Thailand. Thus, prospective epidemiologic information is needed for developing more effective public health interventions. A cohort study to identify incidence and risk factors of O. viverrini infection was conducted in a rural community in Thailand during December 2002-February 2004. The incidence rate of opisthorchiasis was 21.6/100 person-years. The independent factors associated with opisthorchiasis were an age > 60 years and consuming chopped raw fish salad (Koi pla). Thus, avoiding this raw fish salad should be emphasized in the national control program.

Background: Opisthorchis viverrini infection is still one of the public health problems in Thailand. Our recent cohort study conducted in a rural community in central Thailand showed that the incidence rate of O. viverrini infection in 2002-2004 was 21.6/100 person-years. Conventional control activities including case diagnosis and treatment, hygienic defecation promotion and health education focusing on avoiding raw fish consumption was implemented. This study aimed to re-assess the status of infection after implementation of intervention programs, using both quantitative and qualitative methods in [2007][2008][2009]. Methods: A prospective cohort study was conducted to evaluate the incidence and risk factors of O. viverrini infection. Stool examination methods including wet preparation, Kato and formalin-ethyl acetate concentration technique were performed for the detection of O. viverrini eggs. A standardized questionnaire was used to assess risk behavior. In addition, qualitative information was collected from both O. viverrini negative and positive villagers using focus group discussions. Results: The incidence of O. viverrini infection was 21.4/100 person-years. Consumption of chopped raw fish salad, Koi pla and age 60 years and older were independently associated with O. viverrini infection, similar to our previous study. Findings from the qualitative study, indicated that inadequate knowledge, misbeliefs, and social and cultural mores were important factors leading to the maintenance of risk behaviors. Moreover, unhygienic defecation and insufficient diagnosis and treatment were found to facilitate O. viverrini transmission.