A Dilemma for Blastocystis: Asymptomatic or Symptomatic Infection in Humans

Blastocystis presents a great challenge to parasitologists and clinicians to determine whether it is truly an enteropathogen or not and treatment is required if it is observed in symptomatic patients, because even without any treatment patient recovery and improvement has been noted. Blastocystis hominis is the most common protozoan parasite found in patients with gastrointestinal symptoms and also in healthy individuals. Communities with poor hygiene, lack of safe water supply and proper sewage system show a higher prevalence. Although its distribution was almost equal in a study; 53.6% asymptomatic and 46.4% symptomatic, but in a different study from Turkey, 70.2% of patients were found symptomatic. According to some reports, in children Blastocystis infection should be considered as a prominent causative agent of gastrointestinal disturbances. B. hominis has been established as a probable causal agent in patients of Irritable Bowel syndrome. Several issues about this parasite such as the clinical relevance, pathogenicity and the need for treatment are much debated and still unresolved. Metronidazole appears to be the most effective drug for treatment of Blastocystis infections despite some evidence for treatment failure. In such circumstances, nitazoxanide and TMP-SMX may be considered as second choice of drugs.