Blastocystis is an anaerobic unicellular protozoal parasite infecting the gastrointestinal tract of humans and a wide range of animals. It is one of the most common enteric microorganisms with higher prevalence rates in developing than in developed countries. Feco-oral is the main route of transmission where low socioeconomic conditions, poor hygienic practices, close contact with animals, and drinking contaminated water act as major risk factors. Infection with Blastocystis was demonstrated in both symptomatic and asymptomatic people. For a long period, Blastocystis was considered a commensal organism with no pathogenic role, but recently, many studies linked it to different gastrointestinal symptoms such as nausea, diarrhea, and abdominal pain. Association with irritable bowel syndrome and colorectal cancer was also reported.

This study aims to:

- Identify subtypes of human Blastocystis isolates in Sohag by using RFLP-PCR and provide additional information on the molecular epidemiology of this parasite in our locality.

Inclusion Criteria:

• Patients from outpatient clinics, Sohag hospitals.

Exclusion Criteria:

• Patients received antiparasitic drugs in the last two weeks

samples will be collected from outpatients with any age & sex groups from different locations (cities and villages).