Blastocystis in Swiss children: a practical approach

Blastocystis is a parasite with a worldwide distribution and a varying prevalence in different countries. The pleomorphic nature of the protozoon and the lack of understanding a possible pathogenesis have led to confusion regarding its clinical significance. The aim of the study was to shed light on clinical characteristics of pediatric patients in Swiss children with a positive stool sample for Blastocystis, in order to provide recommendations for a practical approach for the clinician to know whom, when, and how to test. This is a retrospective study of pediatric patients, whose stool has been tested positive for Blastocystis in the last 10 years in northern Switzerland. A total of 4047 stool samples, belonging to 1887 different patients, were analyzed; 240 stool samples (of 160 patients) were tested positive for Blastocystis. On average, 2.2 (CI 1.98–2.35) stool samples per patient were analyzed, of which 1.48 (CI 1.36–1.61) were positive for Blastocystis. In 63% abdominal pain was the leading symptom, while in 17.5% it was an accidental finding without symptoms. There was a high significance in correlation of abdominal pain and chronicity (p < 0.0001) but none in diarrhea (p = 0.082) nor nausea/vomiting or other symptoms and chronicity. Followed by Entamoeba coli (8%), 26.3% of the patients with Blastocystis had a co-infection with another parasite, mostly Endolimax nana (13%).

Conclusion: Carriage of Blastocystis is common; therefore, only children/teenagers at risk for a symptomatic Blastocystis infection should be tested. There is a good correlation between Blastocystis and chronic abdominal pain. Children with abdominal symptoms persisting over 4 weeks should have two different stool samples analyzed. No screening after travels/immigration is recommended.