Prevalence and associated factors of intestinal parasitisation: a cross-sectional study among outpatients with gastrointestinal symptoms in Catalonia, Spain

The aim of this study was to report the prevalence of intestinal parasites in stool specimens from outpatients in Catalonia (Spain), and to evaluate the association of age, seasonality, and gender on general parasitisation and by the most frequent detected species. A total of 13,913 samples from 8,313 patients (1-3 specimens per patient) reporting digestive disorders were examined between 1999 and 2005 as a part of medical examinations. Samples were fixed with MIF solution and microscopically examined as wet mounts. Permanent stain was obtained by the modified Ziehl-Neelsen technique for intestinal coccidia. Nineteen species of intestinal parasites were identified. Blastocystis hominis (585 patients) was the predominant species, followed by Giardia duodenalis (321), Dientamoeba fragilis (131), Entamoeba coli (60) and Cryptosporidium sp. (59). Prevalence of helminths was low, being Enterobius vermicularis as the most frequently reported helminth (49 patients). The overall parasitisation was 1,136/8,313 (13.7%); prevalence in adults was 19.8% with a maximum in spring (14.8%). In the adjusted models, age was the main factor associated with infection: adults, with B. hominis and Entamoeba coli (odds ratio (OR)=6.0 and OR=8.5, respectively) and children, with Cryptosporidium and Giardia (OR=2.0 and OR=3.3, respectively). However, seasonality cannot be considered related with infection. The total prevalence was low, taking into account that all the subjects examined presented gastrointestinal symptoms and that species traditionally considered as non-pathogenic were included in the study.