Burden of intestinal protozoan parasites coinciding with Helicobacter pylori infection in patients with gastrointestinal symptoms

Protozoal infections are underdiagnosed contributors to gastrointestinal disease. As their symptoms frequently overlap with those of Helicobacter pylori infection, a leading cause of gastrointestinal illness, coinfections may be overlooked. This study aimed to determine the prevalence of intestinal protozoal infections among patients referred for H. pylori stool testing and to explore their association with clinical symptoms and risk factors.

A cross-sectional study was conducted on 150 patients presenting with gastrointestinal complaints. Stool samples were examined using comprehensive parasitological techniques, along with ELISA for Entamoeba histolytica/dispar and H. pylori antigens.

Intestinal protozoa were detected in 36.9% of participants, most commonly Blastocystis spp. (33.3%), followed by E. dispar (5.3%) and E. coli (2.7%). Giardia lamblia, Dientamoeba fragilis, and Cyclospora cayetanensis were detected in only four patients. All Entamoeba infections were negative for E. histolytica-specific antigen. H. pylori antigen was positive in 35.3% of participants. The prevalence of intestinal protozoa did not differ significantly between H. pylori-positive and H. pylori-negative patients (39.6% vs. 34%); however, Blastocystis spp. was significantly associated with higher H. pylori antigen concentrations. Both protozoal and H. pylori infections were significantly associated with the source of drinking water but showed no significant association with age or sex. Abdominal pain was the predominant symptom among all patients, regardless of H. pylori or protozoal infection status. Notably, 78% of patients referred for H. pylori testing had not concurrently undergone parasitological examination, of whom 37.6% were subsequently found to have protozoal infections.

This study demonstrates a high prevalence of intestinal protozoal infections, predominantly Blastocystis spp., among patients undergoing H. pylori evaluation, and identifies a significant association between Blastocystis and elevated H. pylori antigen levels. The overlapping symptoms and frequent underdiagnosis of protozoal infections in clinical practice support the incorporation of routine parasitological examination alongside H. pylori testing in patients presenting with gastrointestinal symptoms, with the potential to improve diagnostic accuracy and patient management.