TRICHOMONAS HOMINIS: CHARACTERISTICS, MORPHOLOGY, LIFE CYCLE - BIOLOGY - 2025

Trichomonas hominis is a multiflagellate protozoan that lives as a commensal in the intestinal tract of some mammals. It was observed and described for the first time by the English physician Casimir Devaine in 1854. It is also known as Pentatrichomonas hominis due to its structure having five flagella.

It is considered a non-pathogenic organism for the human being since, despite being with certain frequency in the intestine of this, in very few occasions it causes damage and stimulates the appearance of symptoms. However, it is more frequently found in populations settled in warm places and within these, in children under 10 years of age.

Trichomonas hominis. Source: CDC

Taxonomy

The taxonomic classification of Trichomonas hominis is as follows:

• Kingdom: protista
• Edge: metamonada
• Class: parabasalia
• Order: trichomonadida
• Genus: Pentatrichomonas
• Species: Pentatrichomonas hominis

General characteristics

It is single-celled eukaryotic

Trichomonas hominis is a unicellular organism, which means that it is made up of a single cell. That cell is of the eukaryotic type. This implies that their genetic material is bounded by a membrane, enclosed in a cellular organelle known as the nucleus.

Is a parasite

Being a parasite, this protozoan necessarily needs another living being in order to survive. In this case, it lodges in the intestinal tract of some mammals and benefits from the products of their digestion.

Despite this, it could almost be said that he lives under a commensal relationship, since there are very few occasions in which he triggers a pathological reaction.

Habitat

Trichomonas hominis is found in the large intestine of some mammals such as man and some rodents. The area of ​​the large intestine in which this protozoan tends to be located is in the cecal area.

From a geographical point of view, the protozoan is abundant in places with a warm climate.

Nutrition

Trichomonas hominis is a heterotrophic organism. It feeds on the substances that circulate through the digestive tract of mammals that it parasitizes.

Feeding is carried out via phagocytosis. Through this process, the protozoan surrounds the food particles with its plasma membrane and incorporates them into its cytoplasm so that they can be processed by the digestive enzymes inside the protozoan.

Reproduction

In this type of protozoa, the reproduction that is observed is asexual, it does not require the union of gametes.

The process by which Trichomonas hominis reproduces is longitudinal binary fission. In this, the duplication of protozoan DNA occurs. Subsequently each copy goes to one end of the cell and it begins to lengthen.

Finally, the cytoplasm undergoes a strangulation along the longitudinal axis, until the cell divides completely, originating two cells that are genetically identical to the progenitor.

Morphology

The protozoan Trichomonas hominis only has one life form in its life cycle, the trophozoite <that is, it does not present cysts.

The trophozoite has a shape similar to that of a pear. It has approximate measurements between 5-15 microns, although some have been recorded that have reached up to 20 microns. Likewise, it is a cell with a single nucleus, which is located towards the anterior pole of the cell.

The nucleus is associated with an endosome; a set of vesicles that have been generated through endocytosis that contain material that has been captured outside the cell.

Seen under the microscope, it can be seen that it has a total of five flagella, of which one is on the cell surface, forming a kind of undulating membrane. The rest of the flagella are arranged oriented towards the anterior pole.

They have a structure known as axostyle, a set of microtubules that are very close together. These run through the entire axis of the cell and can even extend beyond it.

These microtubules are surrounded by a sheet that forms a tube that may or may not be hollow. This structure has a function in relation to locomotion.

Scheme of a Trichonomas hominis trophozoite. (1) Anterior flagella. (2) blepharoplast. (3) Parabasal body. (4) coast. (5) Parabasal fibers. (6) Wave membrane. (7) Posterior flagellum. (8) Hydrogenosomes. (9) Axostyle. (10) Core. (11) pelta. Source: Franciscosp2

Likewise, structures known as blepharoplasts, basal corpuscles from which flagella originate, are observed.

In its cytoplasm it does not present mitochondria, but a Golgi apparatus, which is called the parabasal body.

Biological cycle

This protozoan has several possible hosts, all mammals: rodents, dogs, and primates, like man. However, flies can sometimes act as indirect vectors, as they frequently carry fecal remains on their limbs.

The site of the human body where this protozoan is found is the large intestine, mainly the cecum. There it feeds on intestinal contents. It is always in the trophozoite state, since it does not present cysts.

Trophozoites are released through the feces. They can be ingested by a new host when he ingests food or water contaminated with fecal particles infested with Trichomonas hominis trophozoites.

Once inside the organism of the new host, the trophozoites are transported through the digestive tract to the large intestine, finding their ideal habitat. There they begin to reproduce and spread through the large intestine, although their favorite site is the cecum.

Later they are expelled with the feces so that the cycle continues.

Infection

Trichomonas hominis is a protozoan that generally does not cause any pathology. However, when for some reason it begins to reproduce in an uncontrolled way, considerably increasing its number in the intestine with the consequent irritation of the intestinal mucosa.

Transmission

The main mechanism of transmission of Trichomonas hominis is through the ingestion of food and water contaminated with stools containing trophozoites.

Symptoms and signs

An individual can be infected with Trichomonas hominis without presenting any type of symptoms. This is what happens most frequently, since this is a non-pathogenic protozoan for humans.

Despite this, when the number of parasites is very abundant, they tend to erode and inflame the intestinal mucosa, with the consequent diarrheal-like symptoms:

• Frequent, pasty-liquid stools
• General discomfort
• Abdominal cramps in extreme cases.

Diagnosis

The main way to diagnose Trichomonas hominis infection is through the study of fresh stool. Once the sample is obtained, it is observed under the microscope to identify the presence of protozoan trophozoites.

Stool tests are the best diagnostic option. Source: Bobjgalindo

Likewise, there are other diagnostic methods, among which the stool test or stool culture stands out. In this, a culture with stool samples is carried out in order to detect any microorganisms that grow there.

Treatment

The finding of Trichomonas hominis in the stool may be accidental in some routine examination. Doctors choose not to prescribe any treatment if the individual does not present any symptoms.

However, if your finding is linked to the persistence of any intestinal symptoms such as diarrhea or colic, it is necessary to use some medication.

In this case, the drugs to treat intestinal parasites are almost always the same. Among the most used is metronidazole, an antiparasitic whose mechanism of action focuses on nucleic acids, inhibiting their synthesis and therefore, preventing the multiplication of protozoa.

Other treatment options are tinidazole, secnidazole, and ornidazole.

References

1. Aucott, J., Ravdin, J. (1993). Amebiasis and "nonpathogenic" intestinal protozoa. Infect Dis Clin North Am. 7 (3). 467-85
2. Becerril, M. (2014). Medical parasitology. Mc.Graw-Hill / Interamericana Editores.
3. Bishop, A. (1931). The Morphology and Method of Division of Trichomonas. 23 (2). 129-156
4. Markell, E., Voge, M., and John DT (1990). Medical parasitology. Interamerican. McGraw-Hill. Madrid.
5. Pereira, A. and Pérez, M. (2003). Trichomonosis. Offarm. 22 (4). 11-186
6. Zerpa, R., Huiza, A., Paucar, C., Espinoza, I. and Cabezas, C. (2016). Predatory ability of Trichomonas hominis trophozoites to destroy and / or engulf Blastocystis hominis. Peruvian Journal of Experimental Medicine and Public Health. 33 (1).