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.

A cohort study to identify incidence and risk factors of hookworm infection was conducted in a rural community, central Thailand from November 2005 to February 2007. Stool specimens were examined for hookworm eggs using wet preparation, Kato thick smear, and water-ethyl acetate sedimentation technique. The incidence rate of hookworm infection was 7.5/100 person-years. The independent risk factors for acquiring hookworm infection were barefoot walking (incidence rate ratio [IRR] = 4.2, 95% confidence interval [CI] = 1.2–14.5) and raising buffaloes around the house (IRR = 4.8, 95% CI = 1.9–11.8). Sequencing of internal transcribed spacer 1 (ITS1)-5.8S-ITS2 region of the ribosomal RNA gene were performed for identifying species of hookworm. Necator americanus was the most common hookworm identified in this population. Ancylostoma duodenale and A. ceylanicum were also detected. Our data suggest transmission of both human and animal hookworms in this community. Thus, prevention and control strategies of hookworm infection should cover both human and animal infection.

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.