What is Blastocystosis

Blastocystosis is an infection that is caused by a common parasite,Blastocystis hominis(B. hominis). The parasite lives in the large intestine and can be found in the stool (feces).

It can remain in the body for weeks, months, or years. It is not known whether the parasite B. hominiscauses any symptoms or if the associated symptoms are caused by infection with other parasitic organisms, bacteria, or viruses.

Often, B. hominisis found along with other organisms that are more likely to be the cause of symptoms.

What are the causes?

The way the B. hominisinfection spreads is not fully understood. It may be spread through contact with water or stool that contains the parasite (is contaminated).

What increases the risk?

This condition is more likely to develop in people:

  • Who live in or travel to places where sanitation is poor.
  • Who live in or travel to developing countries.
  • Who have frequent exposure to daycare environments or animals.

What are the signs or symptoms?

Many people have no symptoms. If you do have symptoms, they may include:

  • Diarrhea.
  • Nausea.
  • Decreased appetite (anorexia).
  • Abdominal pain, cramping, or bloating.
  • Extreme tiredness (fatigue).
  • Anal itching.
  • Weight loss.
  • Excessive gas.

How is this diagnosed?

Your health care provider will do a physical exam and ask about your medical history and travel history. You will also have stool tests to check for B. hominis. You may need more tests to search for other possible causes of your symptoms.

How is this treated?

If you do not have symptoms, you may not need treatment. Even if you do have symptoms, they may get better on their own over time. If your symptoms are severe or they do not get better over time, you may be prescribed medicines and may need more testing.

Follow these instructions at home:

  • Take over-the-counter and prescription medicines only as told by your health care provider.
  • If you were prescribed an antibiotic medicine, take it as told by your health care provider.Do notstop taking the antibiotic even if you start to feel better.
  • Wash your hands often with soap and water. If soap and water are not available, use hand sanitizer.

Drink enough fluid to keep your urine clear or pale yellow. This is especially important if you have diarrhea.

How is this prevented?

  • Wash your hands with soap and water often. If soap and water are not available, use hand sanitizer. You should wash your hands:
    • Before handling food.
    • After using the bathroom.
    • After having contact with animals.
    • After changing a diaper, even if you are wearing gloves.
  • Before you eat raw fruits and vegetables:
    • Wash them in boiled, bottled, or treated water.
    • Peel them.

When traveling in developing countries:

  • Make sure to drink water that is bottled or treated.
  • Do noteat or drink anything that may be contaminated, including beverages with ice cubes that may have been made from unboiled or untreated water.
  • Do noteat raw foods that have been washed in unboiled tap water.
  • It is safe to drink bottled or canned beverages, such as carbonated beverages, teas, pasteurized fruit drinks, or steaming hot beverages.

Contact a health care provider if:

  • Your symptoms get worse.
  • You lose weight.
  • You develop other abdominal problems.
  • You have a fever.

Get help right away if:

  • You have severe pain in your abdomen.
  • You have diarrhea that does not stop.
  • You have blood in your stool.


  • Blastocystosis is an infection that is caused by a parasite in the large intestine.
  • This condition may develop in people who live in or travel to places where sanitation is poor.
  • To prevent infection, wash hands often, use safe food handling methods, and drink bottled or treated water.
  • If your symptoms continue or they get worse, contact your health care provider.

Sign up to receive the trending updates and tons of Health Tips

Join SeekhealthZ and never miss the latest health information

Scroll to Top