TAENIA SOLIUM: CHARACTERISTICS, MORPHOLOGY, LIFE CYCLE, SIGNS - BIOLOGY - 2025

Taenia solium is a parasite belonging to the phylum of flatworms, specifically to the Cestoda class. It is commonly known as tapeworm and it is located in the intestine of the human being. It can reach measures of up to 4 meters and is responsible for the development of taeniasis and cysticercosis (rare).

In its life cycle it presents an intermediate host, which is often the pig. Thanks to this, the consumption of undercooked pork is one of the main sources of infection. Taeniasis is an easily treatable and eradicable disease. However, it can sometimes become chronic and even cause intestinal obstruction, the consequences of which can be very serious.

Specimen of Taenia solium. Source: Delorieux for Johann Gottfried Bremser

Taxonomy

The taxonomic classification of Taenia solium is as follows:

• Domain: Eukarya
• Kingdom: Animalia
• Phylum: Platyhelminthes
• Class: Cestoda
• Order: Cyclophyllidea
• Family: Taeniidae
• Genus: Taenia
• Species: Taenia solium

characteristics

Is a parasite

Taenia solium is an organism that establishes a relationship of parasitism with others, because it needs another living being to be able to survive. It is an endoparasite because it lodges inside the human body and there it obtains the nutrients it needs, thus harming its host.

Habitat and distribution

This parasite is cosmopolitan. It is present throughout the world. It is especially abundant in those places where pork and beef are frequently consumed. Likewise, in places where brackish conditions are deficient, they are ideal for the proliferation of this parasite.

Now, within the body, the parasite is located in the small intestine. There it develops by absorbing the nutrients from the food that the host eats.

It is hermaphrodite

Both male and female reproductive organs can be seen in the proglottids of Taenia solium. These communicate so that the process of fertilization and egg formation occurs.

Feeding

Taenia solium is a heterotrophic organism. This means that it does not have the ability to synthesize its own nutrients, so it must feed on substances made by other living beings.

When found in the human intestine, the parasite feeds on the intestinal chyme through osmosis. It mainly absorbs carbohydrates. Likewise, it is important to mention that through the microvilli that surround your body, they optimize this absorption process.

Is pathogenic

This parasite, like all parasites, causes an imbalance in the body, leading to disease. Taenia solium is responsible for two diseases: taeniasis, which is caused by the adult parasite, and cysticercosis, caused by cysts that form in various tissues of the body, such as the brain, muscles, and lungs.

Morphology

The specimens of the Taenia solium have a coloration that ranges between white and ivory. In terms of length, they are quite long, and can reach up to 8 meters. This organism is made up of a body and a head or scolex.

The scolex is generally pyriform in shape and is characterized by four round structures known as suction cups. At the anterior end of the scolex a protuberance can be seen with a double ring of hooks. This structure is called a rostellum. Between the scolex and the body of the parasite there is a space known as the neck.

Taenia solium scolex. The suction cups and the rostellum are observed. Source: 커뷰

Like all plateminths, Taenia solium has a flattened body, which is divided into segments called proglottids. Proglottids that are mature are quadrangular in shape and also exhibit genital pores that are unilateral. They present both types of reproductive structures, both female and male.

The proglottids that are in a more distal position are the gravid. Morphologically, in them the length predominates over the width. These proglottids have a large uterus that has a central branch with several branches. These are full of eggs, between 50,000 and 60,000. The last proglottid ends in a hole known as the foramen caudale.

The eggs have a spherical shape, and are approximately 31 to 41 microns in diameter. Structurally, they have several membranes, including yolk, present only in immature eggs. The yolk is covering the embryophor. Likewise, there is the oncosferal membrane that is covering the Hexacanto embryo.

The Hexacanth embryo is simply the larval stage of the cestodes. In this, the presence of three pairs of hooks can be seen.

Lifecycle

Taenia solium has two hosts, an intermediate host, which can be a pig or a cow, and the definitive host, which is humans.

Humans become infected in two ways: when they consume infected and poorly cooked pork or when they directly eat the eggs. Cysts or cysticerci found in pork are evacuated and the larvae adhere to the walls of the small intestine through the hooks of the scolex.

Here, it takes about two or three months for the worm to fully mature. An adult worm is made up of several segments or proglottids, within which eggs are generated.

The proglottids that are farthest from the scolex are known as gravid proglottids. Inside each one are thousands of eggs, ready to find a new host.

Proglottid. The reproductive system is observed. Source: See page for author

The eggs are able to survive harsh conditions. This is because they are covered by a cementitious type substance. When ingested, inside its hosts, the cementitious layer is digested thanks to the flora of the intestinal tract.

After this process, the embryo is released, which later becomes an oncosphere. Oncospheres penetrate the intestinal wall and enter the bloodstream. Through the blood they are transported mainly to the muscles, the liver or to the central nervous system.

Finally, whatever your destination, you stop and settle down. Here it begins to develop until it reaches the larval stage, known as cysticercus. Within this is the scolex, which contains the cephalic part with the characteristic hooks to attach to the intestine at any time. In these people, the disease known as cysticercosis may develop.

Pathogeny

Taenia solium is a parasite that can generate various pathologies. When it is in adulthood, it causes taeniasis. On the contrary, if it is in its larval stage (cysticercus), it causes a disease known as cysticercosis, which can be fatal.

-Teniasis

It is a parasitic infection that can be caused by several species of the genus Taenia: T. saginata, T. asiatic and T. solium. People with this disease harbor adult Taenia solium in the intestine. These are attached to the intestinal walls through the hooks of the scolex and the parasite absorbs the nutrients that the individual ingests.

Symptoms

Symptoms of Taenia solium intestinal infection are as follows:

• Loss of appetite
• Sickness
• Frequent liquid stools
• Weight loss caused by decreased absorption of nutrients.
• Strong desire to consume salt
• Weakness
• Dizziness

Diagnosis

There are several diagnostic tests to establish whether an individual is infected with Taenia solium. Some of these involve imaging and others collecting samples.

Blood tests

By analyzing a blood sample, the presence of antibodies produced by lymphocytes to fight infection with this parasite can be determined. The presence of antibodies is an unequivocal indication of the presence of the parasite in the body.

Stool analysis

This is a test whose results are quite accurate. Because the parasite lives in the intestine, the proglottids and eggs are shed through the feces.

By microscopic examination of the stool, the eggs and fragments of the parasite can be identified. This is indisputable evidence of Taenia solium infection. However, to establish the diagnosis correctly, it is necessary to collect several stool samples (approximately 3) at different times.

Collection of eggs

It is common that during the medical consultation for these symptoms, the doctor decides to check the anal sphincter, since there it is possible to find parasite eggs. In order to collect the eggs, the doctor takes a transparent adhesive tape designed for this purpose and presses with the adhesive part to the anus to remove the eggs that are there.

Imaging exams

When the parasitosis is very severe and the individual has many parasites in the intestine, tests such as CT scan, ultrasound, MRI, and X-rays can show images of the parasites obstructing the intestine.

Treatment

After evaluating the case, the doctor will decide which are the most suitable medications to eliminate the infection. Antiparasitics are generally prescribed that attack the adult tapeworm, but not the eggs.

These drugs include albendazole and nitazoxanide. Once the treatment is completed, it is necessary to repeat stool tests to verify that the parasite was really eradicated.

-Cysticercosis

Cysticercosis is an invasive infection caused by ingestion of Taenia solium eggs. In the intestine, once they transform into the oncosphere, they invade the bloodstream and are transported to other organs of the body where they form cysts.

Symptoms

Symptoms depend on where the cysts have formed.

Cerebral cysticercosis

• Severe headaches
• Blurry vision
• Seizure episodes
• Alterations when walking

Ocular cysticercosis

• Point vision
• Photophobia
• Blindness
• Blurred or cloudy vision
• Swelling of the retina that can lead to detachment

Cardiac cysticercosis

• Abnormal heart rhythm
• Heart failure

Musculocutaneous cysticercosis

• Localized pain radiating to nearby organs.
• Presence of lumps or lumps under the skin.

Diagnosis

To diagnose cysticercosis, several tests are necessary, in order to reach an accurate diagnosis.

First, blood tests are performed, the most widely used being the so-called western blood. This test uses purified glycoprotein antigens from the cyst; It is very reliable, as it has a sensitivity percentage close to 98% and a specificity percentage of almost 100%.

Likewise, parasite DNA detection tests can also be carried out using the polymerase chain reaction (PCR) technique. The results of this test are quite reliable, but sometimes they turn out to be very expensive, so sometimes they are not available to everyone.

Other very useful diagnostic methods are those that use images. Among these, the one that is most specific is magnetic resonance, since it shows images of lesions that do not even appear on computerized axial tomography (CT).

However, on CT, the cysts are visualized as hypodense images that have very well defined boundaries. On the other hand, calcifications are dot-shaped and hyperdense lesions.

Treatment

The treatment of cysticercosis is much more complex than that of taeniasis. This will depend on the severity of the case. Likewise, the treatment covers various aspects that include eradicating the parasites (as long as the cysts are not calcified) and treating the derived symptoms, such as inflammation and seizures.

Antiparasitic drugs

The medications used are specifically called anthelmintics, such as albendazole. This medicine can help shrink cysts.

Anti-inflammatories

These drugs are used to reduce the inflammation caused by cysts in the tissues in which they are found. Corticosteroids such as dexamethasone are generally used.

Anticonvulsants

If cysts of the parasite are found in brain tissue, seizures may occur. Because of this, anticonvulsant medications are prescribed to solve these episodes.

Surgical excision of cysts

When cysts are in areas that are accessible through surgical interventions, they can be removed. This treatment is especially recommended in cysts found in the liver, eye, or lungs because they can eventually greatly compromise the functioning of these organs.

If the cysts are in the brain, surgery is highly risky, since some area of ​​the cerebral cortex could be injured, with serious repercussions for the individual.

Prevention

The measures to prevent infection by Taenia solium are quite simple:

• Avoid consuming pork or beef undercooked or of doubtful origin. It is important to buy meat from sites that have proper quality control.
• Wash your hands after using the bathroom. In this way infection can be avoided.
• Cook meats to a suitable temperature. For whole cuts, the ideal temperature is around 63 ° C and for ground meat it is up to around 71 ° C. This is a very important point, since these high temperatures help to kill any microorganisms present there.
• Wash your hands before handling and cooking any food.
• Wash and peel fruits and vegetables before consuming them.
• If you travel to places where infection by the parasite is frequent, only drink bottled water.

References

1. Basualdo, J. (2006). Biomedical Microbiology. Editorial Atlante. 1241-1246
2. Del Brutto, O. and García, H. (2015). Taenia solium cysticercosis - The lessons of history. Journal of the neurological sciences. 359 (1-2)
3. Escobedo, A. (2015). Taenia saginata and Taenia solium. Medical Microbiology and Parasitology. 1st edition.
4. García, H., González, A. and Gilman, R. (2003). Diagnosis, treatment and control of cysticercosis by Taenia solium. Journal of the Bolivian Society of Pediatrics. 42 (3).
5. Pradilla, G. (1986). Cysticercosis: clinical, diagnosis and treatment. Uninorte Health. 3 (2). 115-125
6. Sánchez, A., Santiago, J. and Villacastín, B. (2002). Musculocutaneous cysticercosis. REEMO 11 (6). 189-223