Blastocystis is a genus of single-celled protozoan, which its colonization in most cases is asymptomatic. The intestinal colonization of hominis is somewhat common because of the low host specificity of the protozoan.1  Colonization rates differ between developed (10%) and less developed (50%) countries, and it seems to infect people more frequently who work and live with animals.2

Most people with adequate immune systems are asymptomatic carriers. There is much debate in the scientific community if Blastocystis hominis even cause infections in humans or if it is a commensal protozoan. Blastocystosis is an opportunistic infection of the protozoan that can rarely occur. Symptoms of blastocytosis mimic other gastrointestinal illnesses and include:3 4 5

  • Abdominal pain
  • Constipation
  • Diarrhea
  • Fatigue
  • Flatulence
  • Weight loss
  • Food allergies
  • Intestinal inflammation
  • Skin rashes
  • Headaches
  • IBS
  • IBD

Blastocystosis might occur because of an infection of a different more unknown opportunistic strain of Blastocystis. Researchers for the longest time have mislabeled other infectious Blastocystis strains as being Blastocystis hominis, therefore, we might not know which strains are truly causing the infection. Blastocystis hominis could be mostly harmless for all we know, and another strain could be causing all the opportunistic infections.6 7 8

Diagnosis of infection requires a microscoped ova and parasite stool culture and PCR testing.9 10 Only using direct microscopy can lead to misdiagnosis because:11

  1. Amount of shedding microogranisms through stool differ from day to day. You might a less or more serious infection depending on the amount shed on certain days.
  2. Blastocystis may resemble fat cells or white blood cells, which can make detection difficult using microscopes.
  3. Through microscope analysis different strains of Blastocystis can be hard to identify.

PCR testing is more effective and should be used in combination with a stool culture for an accurate diagnosis.

Blastocystis Protocol