TAPEWORM SAGINATA: CHARACTERISTICS, LIFE CYCLE, EPIDEMIOLOGY - MEDICINE - 2025

The saginata is a parasite flatworm of the class Cestoda is acquired through ingestion of meat (raw or undercooked) of infected cows.

This parasite is also known as Taeniarhynchus saginatus or beef tapeworm. The infection of cows is produced by the ingestion of forage or water contaminated by human feces that contain parasite eggs and that, once ingested, are located in the cardiac and skeletal muscles of the animal.

When a person eats meat from infected cows, the tapeworm reaches its reproductive adult stage in the small intestine within 2 to 3 months, and can measure up to 25 meters, although its usual length is usually 4 to 10 meters. It is the largest species in the genus Taenia.

The tapeworm saginata is very closely related to the tapeworm solium, which comes from eating infected or undercooked pork, both tapeworms being commonly known as tapeworms, since usually only a single adult worm is found in the intestine of the infected person, producing a disease called taeniasis.

The first reports regarding the tapeworm saginata date back to 1700 and the first in-depth studies on the subject and its distinction from the tapeworm solium were given to the German zoologist Johann Goeze in 1782.

Both tapeworms, along with the more recently differentiated Asian tapeworm, exhibit many similarities to each other, both in structure and biology, and they all cause tapeworms within the human intestine. However, Tapeworm saginata is larger and longer and, unlike Taenia solium, it does not cause cysticercosis.

Description, physiology and structure of the tapeworm

Tapeworm eggs are found in the feces of infected cattle. They are spherical, 30 to 40 mm in diameter, with a thin yellowish-brown layer and a 6-hook embryo (oncosphere).

It is impossible to distinguish between the eggs of different species of tapeworms. The eggs turn into cysticerci by encysting in the tissues of the infected animal.

The cysticercus is a scolex measuring about 4-6 mm by 7-10 mm and has the appearance of a pearl. Tapeworm in its adult form is only found in humans. It is a parasite with an elongated, segmented worm and generally whitish in color.

Your body is divided into three areas: scolex or head, neck and strobilus (set of rings or proglottids). The scolex is 1–2 mm, has 4 powerful hookless suction cups, a slender neck, and multiple proglottids (chains of multiple body segments) with 20–35 uterine branches each.

The interior of each mature proglottid is filled with muscle layers and entire male and female reproductive systems (hermaphrodites). The most common form of fertilization is self-fertilization.

Once self-fertilized, the male genital tract atrophies and eggs develop inside the uterus, eventually emerging through the excrement or by detaching small segments and exiting through the anus.

Lifecycle

The life cycle begins when the bovine ingests the embryonic egg. This egg can be found in feces, water or sewage or feed and can survive winter in grasslands and in fresh, brackish and salt water, and even survive sewage treatment.

Once in the intestine of the infected animal, the larva passes through the intestinal mucosa and moves through the blood until it remains in an organ or tissue. This cysticercus can remain viable for more than 600 days.

When a person ingests meat with the cysticercus, it is released into the intestine, maturing and reaching its adult form. After this process, they fertilize and release proglottids through the feces, which in turn contaminate the vegetation or water, thus closing the cycle.

epidemiology

Although tapeworm saginata is common worldwide, especially in areas where livestock are raised and their meat is consumed, the incidence has increased in sub-Saharan Africa, Central and South America, Asia and some European countries.

This boom is directly related to the habit of consuming raw or undercooked meat. In some African countries, high percentages of infected cattle in the larval stage have been reported.

Although cattle are the most common intermediate host, tapeworms can also be found in reindeer, llamas, antelopes, wildebeest, giraffes, lemurs, gazelles, camels, and sheep.

Symptoms

The developed and mature parasite remains in its human host throughout its life, constantly absorbing the nutrients from each intake that the person makes.

It can live between 30 and 40 years in the small intestine of the person and, in most cases, there are no symptoms.

The infected person may perceive the spontaneous movement of the proglottids through the anus or expel some segment of the tapeworm in the stool.

The symptoms are not specific or frequent, and may present nausea, headache, epigastric pain, diarrhea, anorexia or pictures of anxiety, dizziness and malaise.

Treatment, prevention and control

In infection with tapeworm saginata, man is the mandatory definitive host, spreading the infection to intermediate bovine hosts.

It is not transmitted from person to person and there are no immunization routes yet, although vaccines to combat the infection in cattle are still being experimented on.

Among the labor sectors at risk are livestock, zoos, veterinary medicine, animal welfare and shops, as well as the processing and preservation of meat and the production of meat products.

The cysticercus dies when the meat is subjected to temperatures greater than 60ºC or when it is kept for at least 10 days at a temperature of -10ºC. As for the eggs, they remain inactive when they remain for a few hours at 55ºC.

Regarding its detection, it is very important to monitor the symptoms. There is currently no quick and easy way to diagnose human taeniasis. Coproscopic examination is usually used, looking for eggs in the stool and in the migration of the proglottids that are expelled through the anus.

Other identification methods include PCR (polymerase chain reaction) of species specific sequences of mitochondrial DNA, detection of coproantigens, and immunosorbent assays.

The treatment to eliminate the adult parasite is identical to that used for Taenia solium. It consists of a single dose of praziquantel or niclosamide, although the latter is a lower-spectrum anthelmintic that is not commercially available in some countries.

As preventive measures, it is essential to inspect meat and confiscate infected meat, as well as avoid eating raw or poorly cooked meat, washing hands thoroughly after using the bathroom and before handling and eating food.

References

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