Prevalence, subtype distribution, genetic characteristics and associated factors of Blastocystis colonization in type 2 diabetes mellitus patients and non-diabetic controls in Zhejiang, China

Blastocystis is a ubiquitous enteric protist with debated clinical relevance. Epidemiological data on Blastocystis colonization in patients with type 2 diabetes mellitus (T2DM) remain scarce in eastern China. This study aimed to characterize the prevalence, subtype distribution, genetic features and associated factors of Blastocystis colonization in T2DM patients and non-diabetic controls in Zhejiang, China. In this case-control study, 359 T2DM patients and 188 age- and sex-matched non-diabetic controls were consecutively recruited. Blastocystis colonization was detected by PCR targeting the small subunit ribosomal RNA (SSU rRNA) gene; subtypes were determined via Sanger sequencing and phylogenetic analysis. Between-group comparisons were conducted using Pearson’s χ² test or Fisher’s exact test. The overall prevalence of Blastocystis colonization was 4.74% (17/359) in T2DM patients and 3.19% (6/188) in controls, with no statistically significant difference (P = 0.438). Across the study population, rural residents had a significantly higher colonization rate than urban residents, and this pattern was consistent in both the T2DM (6.20% vs. 0.99%; P = 0.037) and control groups (4.51% vs. 0.00%; P = 0.174). T2DM patients with disease duration ≥ 10 years had an ~ 4-fold higher colonization prevalence than those with shorter duration (6.47% vs. 1.57%; P = 0.037). Among 23 positive isolates, ST3 (69.57%) was the predominant subtype, followed by ST1 (30.43%). All control isolates were ST3, while ST1 was exclusively detected in the T2DM group. ST1 showed higher genetic diversity, with three alleles versus two in ST3. Blastocystis colonization is relatively uncommon in both T2DM and non-diabetic populations in this coastal Chinese region, with no significant intergroup prevalence difference. Rural residence is a shared factor associated with colonization, while longer diabetes duration is a T2DM-specific factor associated with colonization. These findings support targeted surveillance and health education for diabetic patients with long disease duration and rural residence.