The continuous life cycle of the pork tapeworm is a closed chain that can be easily broken if you thoroughly examine the weaknesses of each link. A dangerous parasite during its life goes through several phases of development, changing the environment and its carriers. The main habitat of the tapeworm is the human small intestine, in which adult helminth parasites up to 20 years. The larval form lives in pigs and other animals.
Main stages of the cycle
Due to the presence on the head of the parasite and its larvae of a large number of swiveling hooks, which allow to securely attach themselves to the host's epithelial tissues, the pork tapeworm is briefly called armed tapeworm. Experts attribute it to the class of Cestoda parasitic tapeworms, which are extremely common in nature.
Among the stages of the life cycle of the helminth can be identified:
- formation of the reproductive system in proglottids of an adult individual;
- egg formation and fertilization;
- bringing them together with the strobilae to the external environment;
- intermediate host infection;
- development of the larva and its encapsulation in the form of cysticercus;
- Cysticercus in the body of a permanent carrier (person);
- tapeworm growth and the formation of breeding proglottids.
The development cycle of the pork tapeworm envisages the presence of the larval phase, which passes through the muscle tissue of the intermediate host, which is the pig or other animals. In the small intestine, the acidity of the environment is optimal for the life of this parasite, and the presence of a large amount of nutrients allows it to grow at a rate of 5-8 cm per day.
Permanent and temporary hosts
The size of an adult worm can reach 8 m (usually 2-3), and its lifespan can last for 20 or more years.
The parasite produces a huge number of eggs, which, along with fecal masses, are excreted into the external environment, infecting the soil and water.
Eggs of pork tapeworm are spread by small animals and insects, along with food, into the stomach of an intermediate carrier. Wildlife and domestic pigs, dogs, camels, hares, rabbits, and people can become owners of the larval form of the parasite.
Due to the presence of special hooks, the larva that emerged from the egg, along with the blood, is spread through the tissues and organs. The intermediate host is infected with cysticercosis, in which cysticists accumulate in its muscle tissues, which are hidden in the chitin capsule of adult individuals.
No sex required for sexual reproduction
The scheme of the life cycle of the pork tapeworm is great for a parasitic lifestyle, allowing it to spread a huge number of eggs and larvae, some of which are necessarily found intermediate or final hosts.
The adult worm living in the human intestine consists of about 1 thousand proglottid segments that have their own reproductive system.
Each proglottid, formed by the neck of the scolex, begins to grow with distance from the parasite's head, constantly improving its own genitals.
The parasite that has found the host for the first 2-4 months simply grows, and its sexual reproduction does not occur, since at the first stage the developing proglottids have only male reproductive organs in the form of testicles.
It is only after reaching a length of 1 m in the terminal segments that the female reproductive organs begin to form, including triple ovaries and the uterus, which has the appearance of a long hollow tube. More information can be found in the article "On the structure of the pig chain".
As the adult worm grows, the terminal proglottids are drawn out, the size of each fragment reaches a length of 11-15 mm and a width of 6-7 mm. Fertilization takes place inside the segments, and the uterus of the strobila may contain up to 50 thousand fertilized eggs by the time of separation from the maternal individual.
Eggs are spread passively.
After separation from the worm, filled with eggs, the strobila along with the fecal masses from the main carrier come out, getting into public toilets and other places. They do not have devices for movement, but are sufficiently resistant to the influence of the external environment and retain their viability for a long time. They are carried only by other living creatures that have access to human waste.
That is why it is necessary to send the natural needs only in specially designated places in which systematic cleaning and disinfection is carried out.
Together with contaminated water or food, the parasite eggs enter the gastrointestinal tract of the intermediate host, which is mainly a pig (hence the name Pig Chain).
The gastric juice dissolves the protective chitinous shell of the egg, releasing the larva, which has two rows of powerful near-X-ray hooks. Gnawing into the walls of the small intestine, the Finn pork tapeworm punches them, penetrating into the lymphatic fluid or blood, with which it spreads throughout the body.
Getting into the muscle tissue of the larvae of the pork tapeworm absorb the host nutrients, going through a cycle of reincarnations, culminating in the formation of cysticercus.
In most cases, at the intermediate stage of pork chain development, tapeworm larvae are localized in the muscle tissue of animals.
Development in intermediate and mainstream media
Once in the body of animals and humans, the Finns can infect not only the connective tissue, but also other vital organs. Quite often, the parasite is found in the heart, liver, eyes and nervous system.
In the body of an intermediate carrier, the reproduction of a tapeworm does not occur, and its development is limited to the formation of a capsule in which the head and oral organs of the adult worm are located.
The larval form retains its viability for several months, after which it dies without activating the development of the pork chain from the cysticercus.
The chitinous cover of its capsule can be destroyed by an exceptionally high temperature, and then the parasite itself dies, or by the acidic environment inside the body when the cysticercus gets there with food or water.
To move to the next stage, it is necessary that the meat infected with the parasite is eaten without carrying out the necessary processing. Read more in the article "Pork tapeworm: ways of infection and symptoms."
The main feature of the human body is that it can be both the main and intermediate carrier of the pork tapeworm. Consuming along with poorly roasted or raw meat cysticercus parasite, a person becomes infected with an adult form of tapeworm, which is localized in its small intestine.
The tapeworm is constantly growing, reaching a size of 2-3 m.
In the tapeworm, hermaphroditic strobila segments are formed, in which the formation of eggs and their fertilization take place, after which the cycle of reincarnations of the pork tapeworm repeats.
Possible infection by the larval form of the disease
Infection with an intermediate form of the disease or cysticercosis most often occurs when sanitary and hygienic norms are not observed. The eggs of the parasite fall on the hands, through which, together with food, penetrates the gastrointestinal tract. It is possible that eggs are introduced into the mucous membrane by rubbing the eyes with unwashed hands after visiting a public restroom.
This form of the disease is called cysticercosis, and the parasite that does not reproduce in the human body dies after a few months, filling the vital organs of the host with toxic substances.
Particularly dangerous infection with cysticercus of the brain, which leads to serious headaches and can provoke increased carrier aggressiveness.
There are cases when human cysticercosis was self-infecting. As a rule, this leads to improper treatment of teniasis, in which the patient does not restrain gag reflexes, and the parasite's eggs leaving the small intestine re-enter the stomach.
Prevention at all stages of helminth development
The pork tapeworm that has entered the carrier never leaves it alone. Therefore, it is necessary to conduct timely diagnosis and proper treatment, ensuring disposal of the adult helminth, its larval form and eggs.
More information about this can be found in the article "Methods of treatment of pork tape".
Knowing the life cycle and stages of development of the armed chain, it is quite easy to understand that prevention and compliance with sanitary and hygienic standards are the best way to protect against it.
If you wash your hands thoroughly after visiting the restroom, talking with animals and before eating, and also carry out regular cleaning and disinfection of your toilet, then the risk of infection with cysticercosis decreases to zero.
To protect against infection by the adult form of the parasite, you should abandon the use of raw, dried and poorly roasted meat, especially very popular steaks with blood.
It is necessary to acquire pork only in specialized stores and markets that have their own veterinary laboratory and carry out regular carcass tests for the presence of helminth pathogens.
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