What is blastocystis hominis?

Blastocystis hominis is a parasitic protozoan that can live in the human and animal digestive systems. It usually doesn’t cause symptoms, but it can sometimes lead to cramps, severe diarrhea, and gas, among other symptoms, which can result in serious dehydration.

Blastocystis hominis is transmitted through contact with fecal matter from infected people and animals, or by consuming contaminated water or food, causing an infectious disease known as blastocystosis.

Since there are several strains of this microorganism (which is why it is now called Blastocystis spp.), it has not been identified if only some of them are harmful or if the disease only affects people who are sensitive to it, making them more vulnerable to its effects.

In developing countries, it is estimated that more than 21% of the population has this parasite in their digestive tract.

Symptoms of Blastocystis hominis

Although many people carry this microorganism without discomfort, in some cases it can be associated with conditions such as persistent diarrhea, abdominal pain or cramps, bloating, nausea, fatigue, or changes in bowel habits.

These symptoms can be intermittent and are often confused with those of irritable bowel syndrome, which can make a diagnosis difficult.

The intensity of the discomfort can range from mild to severe and is sometimes accompanied by loss of appetite or loose stools with mucus. There may also be a feeling of incomplete bowel evacuation or an urgent need to defecate.

Although it is not clear if these symptoms are always caused by Blastocystis hominis—as it can coexist with other infections or intestinal disorders—it is important for the clinical diagnosis to be made properly.

The diagnosis of Blastocystis hominis is made through laboratory tests on stool samples, mainly by a coproparasitoscopic exam, which identifies the presence of intestinal parasites under a microscope.

However, due to the large number of organisms that may be present in the stool, it is usually recommended to analyze at least three samples collected on different days. This increases the probability of detection.

More sensitive techniques, such as a polymerase chain reaction (PCR), can be used to identify the protozoan’s genetic material and distinguish between different subtypes.

It is important to note that the presence of Blastocystis hominis in the stool does not always mean it is the cause of the symptoms. For this reason, the diagnosis must consider the patient’s clinical context, their symptoms, travel history, consumption of contaminated water or food, and the exclusion of other gastrointestinal causes.

Treatment for Blastocystis hominis is not always necessary, especially if the person is asymptomatic.

If a person has persistent or bothersome symptoms that cannot be attributed to another cause, antiparasitic medication may be prescribed. The response to treatment can vary as there are different subtypes of the parasite, some of which may be more resistant or less pathogenic.

If there is resistance or recurrence, combination therapies or a re-evaluation of the diagnosis may be considered to rule out other infections or functional disorders.

It is essential that treatment is supervised by a healthcare professional, as not all cases require medication or the use of antiparasitics, which if used incorrectly can cause side effects or lead to resistance.

It is also important to understand that symptom relief may not be immediate and requires clinical follow-up to assess the effectiveness of the treatment and the potential need to repeat studies.

Beyond providing treatment for Blastocystis hominis, it is also important to implement preventive measures that focus on improving personal hygiene and basic sanitation. Washing hands with soap and water before eating, after using the restroom, and when handling food is essential, along with drinking safe water and avoiding raw or poorly washed foods.

At the Internal Medicine department at ABC Medical Center, we can provide you with specialized care. Contact us!