Intestinal protozoa in celiac disease: Detection and phylogenetic characterization

Objective: Celiac disease (CD) is a chronic, immune-mediated enteropathy of the small intestine and may be associated with parasitic infections. This study investigated the prevalence of intestinal protozoan parasites in patients with CD and evaluated genetic variation using phylogenetic analysis. Materials and Methods: We screened stool samples from patients with CD for Entamoeba histolytica , Entamoeba moshkovskii , Dientamoeba fragilis , Blastocystis hominis , Giardia intestinalis , Cryptosporidium parvum , Cystoisospora belli , and Cyclospora cayetanensis using microscopy, serology, quantitative polymerase chain reaction, and DNA sequencing. We performed phylogenetic analyses in Geneious (v9.1.3) and conducted statistical analyses in IBM SPSS Statistics (v20). Results: Among 74 patients, positivity for D. fragilis and B. hominis was significantly associated with CD ( P = 0.005). Positivity rates for these parasites differed by sex and were higher in female patients. Sequence analysis identified three subtypes. Our isolates showed high similarity to previously reported isolates (mean pairwise identity ≈ 99%) but also contained nucleotide-level variation. Conclusion: Intestinal protozoan parasites may contribute to CD through immune-mediated mechanisms, and the altered intestinal environment in CD may also increase susceptibility to colonization. These findings support a possible association between CD and selected intestinal protozoan parasites.