blastocystis hominis – intestinal parasite

blastocystis hominis

blastocystis hominis

Blastocystis homis is the most common intestinal parasite. About half of people with chronic intestinal symptoms and / or irritable bowel syndrome (IBS) are contaminated with Blastocystis homis. For online laboratory testing for Blastocystis hominis, please contact or Both websites offer high quality DNA tests. DNA research (with the qPCR technique) is about 10% more reliable than the microscopy techniques still used by smaller laboratories.

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Blastocystis hominis, single celled intestinal parasite.

Blastocystis hominis is a single-celled intestinal parasite and is very common in both humans and animals. It is estimated that 25% of people are infected with this parasite.

For a long time it was believed that Blastocystis hominis was harmless. Today we know that this is not the case. There are about 10 subspecies of Blastocystis hominis. Of the 10 subspecies, 2 or 3 subspecies are known to cause complaints. The other subspecies may cause no complaints, although it is possible to be allergic to Blastocystis hominis and the parasite may pose a problem to those people with the allergy. New techniques are being developed to distinguish the harmful variants of Blastocystis hominis. The Blastocystis hominis intestinal parasite does not cause serious illness, but can cause chronic intestinal symptoms. The most common symptoms are abdominal distention and flatulence.

What does Blastocystis hominis look like?

Blastocystis hominis appears to be a blank cell, and looks like a yeast cell under the microscope. For this reason it took a long time before scientist finally concluded that Blastocystis is in fact an intestinal parasite. Even though Blastocystis hominis does look like a yeast cell, it is nevertheless remarkable that it took so long to reach the conclusion that it is a parasite, because Blastocystis hominis features the typical parasite properties. The cells of the parasite which can only be grown on a culture medium for parasites, and not to a yeast culture medium. Moreover, Blastocystis hominis makes cysts (also this is a typical characteristic of parasites). Finally, Blastocystis hominis can only be killed with paracidal medications.

The size of Blastocysts may range from 2 microns to 100 microns. The yeast-like form is the most common. The cell can accumulate starch and is then filled with granules. Blastocystis hominis may even take the form of an amoeba. When this happens,  they look so much like white blood cells that they hardly can be distinguished. This form is rarely seen.

New methods of Blastocystis hominis detection

Thanks to improved analytical methods and studies of the DNA of the parasite, recent research done in the past years have shown that Blastocystis hominis, counts 10 genetically distinct subtypes. This is partly due to the fact that both animals and humans can become infected with Blastocystis hominis.

Until recently, only microscopic examination was available (the so-called TFT, triple faeces test). This test has limitations. The stool can also be examined for parasites by means of DNA techniques. This analysis method can replace microscopic examination. Only by making use of genetic techniques, can one identify the different subtypes of Blastocystis hominis. DNA techniques have a high added value.

Up to now, has shown that there are two subtypes that are harmful to the health. These variants of Blastocystis hominis can cause many symptoms.

Intestinal Complaints caused by Blastocystis hominis

Dientamoeba fragilis and Blastocystis hominis cause abdominal distension
Dientamoeba fragilis and Blastocystis hominis can cause intestinal complaints such as abdominal distension.

Besides the most common symptoms – abdominal bloating accompanied with flatulence – Blastocystis hominis infection causes many more irritable bowel symptoms. Among the symptoms are included: abdominal pain, diarrhea, nausea, fatigue, insomnia and even fever. If allergic to Blastocystis hominis, itching can also be caused by the allergic reaction.

Blastocystis hominis infection often causes irritation of the intestinal mucosa. One reason for this is that Blastocystis hominis infections are caused by bacteria.

Like other single celled intestinal parasites, Blastocystis hominis produces a type of alcohol. The body metabolizes alcohol into acetaldehyde, a substance that contributes to stomach aches and fatigue. A large stock of publications on Blastocystis hominis indicates that approximately 1 in 3 people infected with the parasite experience chronic irritable bowel symptoms. But it is still a relatively new discovery that there are 10 different variants, of which only two are harmful: this may explain why not everyone experiences symptoms.

It is noteworthy that Blastocystis hominis infection occurs more frequently among people who arealso infected with Dientamoeba fragilis. Upon discovery of a Blastocystis hominis, it may make sense also for testing to be undertaken for Dientamoeba fragilis.

Diet for Blastocystis hominis

Once infection with a harmful variant of Blastocystis hominis occurs it is usually necessary to make adjustments to the diet. Most important is that the consumption of sugar and starch are omitted as much as possible. This is because most symptoms are caused by the intestinal parasite turning sugar and starch into a toxic alcohol.

Converting sugar into alcohol is a form of fermentation – the process is similar to brewing beer for example. During the fermentation gasses are released. This is the cause of bloating and flatulence. The internal pressure of the gasses cause an uncomfortable feeling, and flatulence. The symptoms can be embarrassing and debilitating.

Intestinal parasites convert sugars into alcohol as one of the consequences of the cell division of Blastocystis hominis. So by eating a lot of sugar and starch increases not only the symptoms, but also the numbers of intestinal parasites. It is of importance to avoid as much as possible sugar, bread, potatoes, and pasta. This will slow down the cell division.

Blastocystis hominis does not disappear completely, simply by adjusting the diet. There are also medications needed. Nowadays, many harmful microorganisms have become resistant to the medication, so it is very important to combine medication with the right diet: diet and medication can work complementary to each other. It’s a shame to take medication, while the growth of intestinal parasites is simultaneously stimulated with the wrong diet.

Laboratory testing for infection with Blastocystis hominis

Blastocystis hominis is a very simple, one-celled organism. It looks a bit like an “empty” cell. The name Blastocystis hominis also alludes to this: blasto means “cavity”. The intestinal parasite can only be detected via stool sample examination by a specialized laboratory.

Few laboratories have the correct techniques to detect Blastocystis hominis. The intestinal parasite can only be detected by means of genetic testing, such as qPCR. The different types of Blastocystis hominis are difficult to identify under the microscope.

The most reliable method (qPCR) makes no use of microscopy. Instead,  special equipment is used to search for the DNA of the parasite. Although the intestinal parasite sometimes cannot be identified under the microscope, it’s DNA can still be found.

More importantly, DNA helps by determining the subtype of Blastocystis hominis which is present. Since only 2 of the 10 known variants have been proved harmful, the laboratory must be able to distinguish between the different variants of the DNA – this is nearly impossible by means of microscopy alone. The laboratory that is the most specialized in the Netherlands is MGlab.