Epidemiology and clinical characteristics of intestinal parasites among patients of a medical center in central Taiwan: a retrospective study of Blastocystis infection

BACKGROUND: Intestinal parasitic infections remain among the most common infectious diseases worldwide, posing significant public health challenges. Blastocystis spp., in particular, has emerged as the most prevalent microorganism detected in human stool examinations in recent years. Accumulating evidence suggests a potential association between specific Blastocystis subtypes and gastrointestinal disturbances. This study aimed to assess the current epidemiological profile of intestinal parasitic infections in Taiwan and to explore potential associations between parasitic infections and chronic diseases. METHODS: A retrospective analysis was conducted using 1498 parasite-positive stool reports from 1265 patients who underwent stool examinations at Taichung Veterans General Hospital (TCVGH) between January 2012 and December 2023. Stool specimens were examined using the merthiolate-iodine-formaldehyde (MIF) method, as recommended by the Taiwan Centers for Disease Control. Demographic and clinical data were collected to evaluate infection patterns, stool specimen positive rate, and species distribution across different patient subgroups. RESULTS: During the 12-year surveillance period, the average stool specimen positivity rate was 0.9%, ranging from 0.46 to 1.54%. The majority of infected individuals (81.43%) were local Taiwanese residents. Young adult males (aged 18-64 years) had a higher risk of infection. Blastocystis spp. represented the predominant parasite, accounting for 87.19% of all identified cases, followed by Giardia lamblia (9.16%). Coinfections were observed in 18 of the 1265 cases, with Blastocystis spp. and Endolimax nana being the most frequent co-infecting species. CONCLUSION: Although the overall positive rate of intestinal parasitic infections in Taiwan remains low, the data indicate a distinct compositional shift in parasite species, highlighting Blastocystis spp. as the leading organism in human infections. These findings underscore the need for comprehensive investigations into the epidemiological, molecular, and pathophysiological characteristics of Blastocystis to elucidate its clinical significance and potential role in gastrointestinal disorders.