Blastocystosis: Epidemiological, clinical, pathogenic, diagnostic, and therapeutic aspects

Blastocystis is a nonmoving pleomorphic stramenopile or chromist. Nineteen subtypes of this organism have been identified. It has a worldwide distribution. The prevalence rates in humans are lower than 1% in developed countries and up to 100% in developing countries. It is possible to recognize the fecal-oral transmission, through ingestion of contaminated food and water, and zoonotic spreads. The diagnosis is carried out by direct fecal examination, culture and molecular techniques. Blastocystis has virulence factors such as cysteine proteases, serine proteases and legumains, mostly secreted to the pathogen-host interface. This stramenopile has been linked to gastrointestinal symptoms, irritable bowel syndrome, urticarial and arthritis. However, there is not any conclusive evidence of association with the disease. Recently, the hypothesis of the opportunistic pathogen has emerged. Treatment has traditionally been based on metronidazole and other imidazoles. The recent obtaining of the nuclear genome will allow the rational development of new effective drugs. The aim of this review is to highlight the main epidemiological, clinical, pathogenic, diagnostic and therapeutic aspects of the Blastocystis infection.