TRICHURIS: CHARACTERISTICS, MORPHOLOGY, HABITAT, SPECIES - BIOLOGY - 2025

Trichuris is a genus of parasites belonging to the phylum Nematoda that is made up of round worms. These lodge in the intestines of some mammals such as humans and some domestic animals such as dogs and cats. They have blood-sucking habits and are sexually dimorphic.

The genus was described for the first time in 1761. It is made up of about 20 species, of which the best known is Trichuris trichiura, which parasitizes the large intestine of humans.

Trichuris trichiura specimen. Source: Delorieux for Johann Gottfried Bremser

Despite the fact that these organisms are pathogenic parasites, they have also been used in various therapeutic treatments to treat ailments that have to do with the gastrointestinal system, the nervous system and the immune system.

Taxonomy

The taxonomic classification of the genus Trichuris is as follows:

- Domain: Eukarya.

- Animalia Kingdom.

- Phylum: Nematoda.

- Class: Enoplea.

- Order: Trichocephalida.

–Family: Trichuridae.

- Genus: Trichuris.

characteristics

Individuals of the genus Trichuris are eukaryotic multicellular organisms. This means that they are made up of various types of cells, and that in these the genetic material is enclosed in a structure known as the cell nucleus.

Similarly, the different species that make up the genus are triblastic. During the stages of embryonic development, the so-called germ layers appear: ectoderm, mesoderm and endoderm. From each layer develop the different organs that will make up the structures of the adult specimens.

On the other hand, the organisms of the species that are grouped in the genus Trichuris are dioecious. This means that they have separate sex: there are male and female specimens, with their respective morphological differences.

Members of this genus are considered pseudocoelomates. The general cavity does not originate from the mesoderm. In addition, being filled with water, it can even function as a hydrostatic organ, facilitating the displacement of the parasite.

If an imaginary line is drawn along the entire longitudinal plane, it can be seen that both halves of the animal are exactly the same. This allows us to affirm that these animals have bilateral symmetry.

Likewise, they are endoparasites, since they are housed inside a host, on whose blood they feed.

Morphology

Members of the genus Trichuris are also known as "whipworms." Like the rest of the members of the phylum Nematoda, the genus Trichuris is made up of round worms.

Likewise, most of the species present a marked sexual dimorphism. Generally, the adult female specimens are larger than those of the male gender. For example, in the Trichuris suis species, the female can measure up to 8 cm, while the male is about 4 cm.

The body of the female has a straight rear end, while the rear end of the male is spiral shaped (in most species).

Similarly, the anterior end of the parasite is thin and represents a high percentage of the total body of the adult animal.

Eggs

The eggs of members of this genus are barrel-shaped; that is to say, widened in the center and with the ends of reduced width. At these polar extremes, mucous plugs are observed that have the objective of protecting the interior of the egg. They also have a coloration that is between brown and honey.

Trichuris egg. Source: PD - DPDx Image Library;

Habitat

Parasites of the genus Trichuris are found in the intestines of some mammals. The habitat of most species is the large intestine of different animals. Some are located at the level of the cecum, such as Trichuris vulpis; and others at the level of the colon, such as Trichuris trichiura.

Representative species

The genus Trichuris encompasses approximately 20 species. However, not all have been studied to the same depth. The best known species, especially for the role they play in some human and animal parasites, are the following: Trichuris trichiura, Trichuris serrata, Trichuris suis and Trichuris vulpis.

Trichuris trichiura

It is the best known species of the genus Trichuris. This is because this parasite is responsible for one of the most studied parasites in man.

This animal is also known as the whipworm, due to its shape. Like all members of the genus Trichuris, this species is sexually dimorphic, with the female being much larger than the male.

Likewise, it colonizes the colon of human beings, generating inflammation and feeding on the blood of its host, since it is hematophagous. Because of this, one of the most obvious signs of infection is anemia.

Trichuris serrata

This is an almost exclusive species of domestic cats. Its geographic distribution is believed to be limited to South America, North America, the Caribbean Islands, and Australia. In this species, the female can reach up to 5cm in length, while the male is only about 4cm long.

Although Trichuris serrata infects cats, it does not generate a significant infection in them, since it does not even cause the appearance of symptoms.

Likewise, it has a certain relationship with another species of this genus, Trichuris campanula, which also affects felines. However, thanks to the morphological differences between their specimens, a differentiation can be made between both species.

Trichuris suis

It is the so-called pig worm. The parasite is located in both the small and large intestines, although they are more frequently found in the latter, specifically at the level of the cecum and colon.

A curious fact about this species is that it is widely used in some experimental therapies to treat certain intestinal pathologies, such as Crohn's disease and colitis.

In these cases they act by reducing the inflammation of the tissues affected by these pathologies, as well as regulating the immune response. However, this treatment is still in the experimental period.

Trichuris vulpis

This species infects members of the Canidae family such as wolves, foxes, and especially dogs. As with the rest of the parasites of the genus Trichuris, it lodges in the large intestine of its host, specifically in the cecum. These parasites have a pale coloration, and the female can reach up to 9 cm.

References

1. Botero, D. and Restrepo, M. (1998) Human parasites. Corporation for Biological Research. 3rd edition.
2. Curtis, H., Barnes, S., Schneck, A. and Massarini, A. (2008). Biology. Editorial Médica Panamericana. 7th edition.
3. Mehlhorn, H. (2015). Trichuris, chapter of Encyclopedia of Parasitology.
4. Stephenson, L., Hollad, C. and Cooper, E (2000) The public health significance of Trichuris trichiura. Parasitology 121 (1) 573 - 595
5. Summers, R., Elliot, D., Urban, J., Thompson, R. and Weinstock, J. (2004) Trichuris suis therapy in Crohn's disease. BMJ Journal. 54 (1)