BLASTOCYSTIS HOMINIS: A MYSTERIOUS AND COMMONLY DISREGARDED PARASITE

Abstract

Blastocystis hominis (B. hominis) is an anaerobic, single-cell protozoan, commonly present in human and animal stool samples. It can be found in healthy people as well and it still has not been elucidated whether it is a commensal organism or a pathogen. Blastocystosis is a disease caused by the protozoan in humans. The prevalence of the parasitosis varies both between the countries, and between certain population groups within individual countries. Due to poor hygienic conditions, common exposure to animals and intake of contaminated water and food, people in the developing countries have got a higher prevalence of blastocystosis, but economically developed countries have not been spared either. The taxonomy of B. hominis is still a matter of debates. For the reasons of genetic diversity, it has been suggested that the name B. hominis should be replaced with „Blastocystis species‟. Seventeen subtypes of the species have been so far identified, and a definitive characterization of Blastocystis spp. is possible at the molecular level only. The parasite is transferred by the fecal-oral route. A variety of hosts have been identified, and animal-to-human and vice versa transfers have been documented. The most common manifestations of the infection with the organism are diarrhea, abdominal pain, nausea, and bloating. This infection has also been associated with the irritable bowel syndrome (IBS), non-specific colitis, chronic inflammatory bowel disease (CIBD), and urticaria. The diagnosis can be made using the methods of conventional microscopy (CVM), phase-contrast and electron microscopy, cultivation, serodiagnosis, and by using molecular methods. The infection caused by the parasite does not always require treatment. In symptomatic patients, the first line medical treatment is metronidazole. Further studies are required to resolve all dilemmas regarding the parasite.