Clinical and epidemiological characteristics of intestinal parasite infection by Blastocystis hominis

Objectives: Blastocystis hominis (B. hominis) is one of the most common intestinal parasites isolated in humans. The parasite can cause gastrointestinal symptoms or, in most cases, remain asymptomatic. There are issues concerning the parasite's pathogenic character. The aim of this study was to analyse the clinical and epidemiological characteristics of the parasite infection by B. hominis, with or without other parasitic co-infections.

Patients and methods: An observational retrospective study was conducted of B. hominis isolates in faeces from October 2004 to March 2016 in a tropical medicine unit. We reviewed all patients with a parasite infection, exclusively or not by B. hominis.

Results: We studied 3070 patients, 570 (18%) of whom were diagnosed with B. hominis infection, which was the only isolate in 245 (43%) of the 570 patients. A total of 325 (57%) patients presented other parasitic co-infections (Entamoeba histolytic or Entamoeba dispar, Strongyloides stercoralis, hookworm and Schistosoma spp.). The main symptom was abdominal pain (41.8%). In 31.2% of cases, the parasite was detected in the imported diseases screening of asymptomatic patients. Of those who underwent treatment with metronidazole, 78.2% improved. The parasite was neutralised in 82.6% of the patients.

Conclusions: Parasite infection by B. hominis is one of the most common diseases in our tropical medicine unit. Most patients are asymptomatic, or their symptoms can be attributed to other parasite infections. In those cases in which symptoms persist without being able to attribute them to other causes, a specific treatment is recommended.