Blastocystis hominis

Blastocystis hominis

How do I know I have blasto? four_common_forms_of_blastocystis_hominis_valzn

  • abdominal cramps and pain
  • anal itching
  • anorexia
  • bloating
  • diarrhea
  • enlarged liver/spleen
  • fatigue
  • fever
  • gas
  • joint pain/swelling
  • nausea
  • rashes
  • rectal bleeding
  • watery or loose stools

Diagnosing a blasto infection from the presence of symptoms can be misleading and confusing. Blastocystis hominis infection is often accompanied by no symptoms at all. In many cases other parasites are also present along with blasto, creating uncertainty as to the cause of the symptoms. Additionally certain drugs and chemicals cause similar effects as blasto, further blurring the lines as to the real source of symptoms.

Certainly only a minority of people hosting the Blastocystis hominis parasite experience any noticeable symptoms.

What is Blasto?

The debate is still very much alive on exactly what Blastocystis hominis is. Despite being first described as early as 1911, most of the current information on blasto is based on early reports, superficial observations through light microscopes and anecdotal evidence.

Once considered a harmless yeast organism, blasto was confirmed to be a parasitic protozoan (single-celled organism) in 1996. It appears to act in the gastro-intestinal tract as a predator, hunting down other microbes for food. Blasto can remain active in the intestines for weeks, months or years.

How did I get infected?

It is hard to say. Little is known about exactly how blasto is transmitted. Statistics seem to suggest that infection is higher in regions with inadequate sanitation and personal hygiene, suggesting oral-fecal contact. This seems likely, but is yet to be confirmed.

Further evidence suggests that blasto may be spread through infected water and or food, consistent with reports of infection of people traveling to developing countries and wilderness areas. Cross-infection has been reported among family members, institutionalized persons and children in day-care centers, although these incidences have not been clinically confirmed.

Blastocystis hominis has been detected in many different types of mammals, birds and reptiles, including animals commonly in close contact with humans as pets. There is little information available to indicate the likelihood of blasto being transmitted amongst different host species. It is acknowledged that if blasto organisms from animals are capable of infecting humans, then there is a vast potential reservoir in nature for infection of humans.


Infection of humans by Blastocystis hominis is common, and anyone can get infected. Blasto is regarded as the most common of all the intestinal protozoan parasites, but poor laboratory techniques don’t always show true detection results.

Blasto infection appears worldwide, with a greater incidence in tropical, subtropical and developing countries (prevalence rates reported as 30 – 50%). Crowded areas return higher rates of infection.

Developed nations report incidence of blasto infection as 1.5 – 10%. Immigrants, refugees and adopted children from developing countries show higher rates of infection in developed lands, as do those in lower socioeconomic groups or people with lower standards of hygiene. Young adults and immuno-compromised people show higher rates of infection, however immuno-competent people also show susceptibility.

Is Blasto infestation dangerous?

Blastocystis hominis infection can be a long-term parasitic condition, with the blasto parasite remaining in the intestines for weeks, months or even years.

Some reports suggest that blasto may play a role in causing or exacerbating a number of diseases, including enteritis (inflammation of the small intestine), colitis (inflammation of the colon), ulcerative colitis, Crohn’s disease and arthritis. Other reports suggest a link with diabetes and leukemia. Most of these observations are based on single case studies and are yet to be substantiated.

Can I prevent Blasto infestation?

While prevention methods cannot be stated with certainty until more is understood about how this parasite is spread, certain precautions seem to lessen the likelihood of contracting Blastocystis hominis.

  • Wash hands with soap or alcohol-based sanitizer after using the toilet and before handling food
  • Thoroughly wash hands with soap and warm water following changing diapers, especially if you work in child care centers.
  • Avoid water or food that you suspect is contaminated
  • Wash and peel all raw vegetables and fruits before eating

When traveling in countries that are high at risk:

  • Avoid unsterilized water. Drink bottled or canned carbonated drinks (if you break the safety seals yourself), and hot (steaming) coffee and tea
  • Wipe off cans or bottles before drinking of pouring
  • If you need to consume local water, boil it for 10 minutes
  • Mix baby formulas only with bottled or boiled (10 minutes) water
  • Avoid ice cubes or fruit drinks containing unsterilized local water
  • Don’t swim in water that may be contaminated
  • Keep your mouth closed when showering
  • Clean teeth with bottled water
  • Eat foods that are well cooked and served hot
  • Stay clear of food purchased from street vendors
  • Avoid salads, sauces and other food served at room temperature (e.g. buffets)
  • Ensure all meat is thoroughly cooked, including fish and shellfish
  • Do not eat unpasteurized milk and dairy products, including ice cream
  • Stick to fruits and vegetables that are peeled before eating, and peel yourself
  • Avoid sliced fruits that may have been washed in contaminated water
  • Travel with your own water-purification system, e.g. microstrainer filter, or water additive like iodine (be careful not to overuse iodine as too much can be harmful)

Can I be safely treated for blasto?

Treatments are available but not always effective. Owing to the lack of scientific knowledge on the nature of Blastocystis hominis and the exact symptoms it causes, many practitioners suggest that no treatment is required at all.

Nevertheless there are many herbal compounds that have been traditionally applied to protozoan infections, some with a noted action against blasto. These may include garlic, olive leaf, wormwood, clove, black walnut, gentian and echinacea.

One benefit of combining herbal compounds in medicinal doses to combat blasto is the relative safety of these natural chemicals. An ongoing treatment can usually be well tolerated by the patient over an extended course, ensuring a thorough elimination of the parasite.

The typical diarrheal effects of Blasocystis hominis also work in well with an herbal medicine approach. Most natural therapies operate under a time-honored philosophy of weed, seed and feed, including beneficial nutrients, electrolytes and probiotics to replace what is lost through the infection and subsequent cleanse. Diarrhea, common to blasto infection, leads to the loss of vital fluids, salts and minerals. A standard herbal medicine approach works to address these deficiencies as part of an overall strategy.

The highly regulated herbal medicine industries of countries such as Australia and Germany are now leading the way in manufacturing effective herbal treatments to address such parasitic conditions. The development of herbal medicine in these countries often combine the strengths of Chinese, Ayurvedic, American and European traditions, and are manufactured to pharmaceutical standards ensuring quality and efficacy.

Alternative: Antibiotic drugs are typically prescribed for Blastocystis hominis with varying results, including metronidazole (Flagyl). Studies have shown limited success in using metronidazole, while others have indicated resistance to this drug.

Other drugs used include sulfamethoxazole and trimethoprim (Bactrim, Septra, etc.) and iodoquinol (Yodoxin). Iodoquinol is no longer available in certain countries (e.g. Australia) because of its toxicity.

Anti-diarrheal medications are not normally recommended as they can potentially make some diarrheal conditions worse.


Center for Disease Control: Laboratory Identification of Parasites of Public Health Concern: Blastocystis hominis
Mayo Foundation for Medical Education and Research: Blastocystis hominis infection
Smith S., Parasites & Pestilence: Infectious Public Health Challenges – Blastocystis hominis Stanford University
Stenzel DJ, Boreham PF. Blastocystis hominis revisited. Clin Microbiol Rev. 1996 Oct;9(4):563-84.
Ohio Dept of Health Disease Fact Sheet: Blastocystis hominis 2009
Gastrointestinal Assessments: Comprehensive Parasitology Profile Genova Diagnostics 2006
Duke JA, et. al. Handbook of Medicinal Herbs. Second Edition. Boca Raton, FL: CRC Press. 2002.
Jellin JM, Batz F, Hitchens K. Natural Medicines Comprehensive Database. Third Edition. Stockton, California: Therapeutic Research Faculty, 2000.
Privitera JD. “Olive Leaf Extract: A New/Old Healing Bonanza for Mankind.” 1996. (Accessed May 31, 2003).
This page is for information only and is not meant to be used for self-diagnosis or as a substitute for consultation with a health care professional. If you have any questions about the disease described above or think that you may have a parasitic infection, consult a health care professional.

Back to Vitaklenz