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Video: The Developmental Cycle Of A Tapeworm: Stages, Types Of Parasites
Adult tape parasites most often infect the human intestine, in some cases they can be found in the pancreas and gallbladder. It is in the host's organism that the life of parasitic forms is divided into several periods, which determine the characteristic development cycle for each group of helminths separately.
- 1 Stages of development of tapeworms
2 Development of various types of parasites
- 2.1 Pork and bovine tapeworms
- 2.2 Dwarf tapeworm
- 2.3 Wide tapes
Stages of development of tapeworms
The life cycle of helminths in most cases is based on infection of the intermediate and final host. The exception to this are Dwarf tapeworms, which are able to actively develop and reproduce in the conditions of only one organism.
There are several life stages in the development of tapeworms.
- The first stage is characterized by the presence of parasitic forms in the organism of the final host. At this time, adults reach their maturity and actively reproduce. Helminth eggs, along with feces, enter the environment.
- The second period is characterized by the formation of larvae in the aquatic environment or on land. The habitat is determined by the individual characteristics of the parasitic forms.
- At the third stage, the larvae enter the organism of the intermediate host along with the contaminated food. After an intermediate lesion, the larva forms into a Finn, which is a worm-shaped bubble, inside which parasitic heads are formed.
- The fourth stage consists in the entry of the helminth into the body of the final host, where the parasitic membrane dies off, segments grow from the heads, with the help of which the worm is attached to the walls of the intestine or internal organs.
Different types of tapeworms have different Finns. There are 5 types of Finn:
- echinococcus - is a large bubble, which contains a huge number of daughter bubbles;
- cysticercoids, which have a body consisting of two parts - front and back. The front part is characterized by a convex wall with a scolex, the back part is characterized by the presence of a small tail;
- cysticercus, which is a fluid-filled bladder. One of its walls is necessarily turned outward and equipped with a scolex;
- cenuras have a structure quite similar to cysticercus, with the exception of the presence of many scolexes;
- plerocercoids - characterized by a longer body, equipped with a scolex on one side.
Development of various types of parasites
Among the most common tape parasitic forms are dwarf tapeworms, tapeworms (pork and bovine), wide tapeworms. Therefore, each developmental cycle of these tapeworms should be considered individually.
Pork and bovine tapeworms
These parasitic forms most often infect the human body. According to statistics, more than 60 million people on the planet are infected with this tapeworm. Most of the infections are observed:
- in developing countries;
- in countries with low hygiene standards;
- in territories where it is customary to eat meat raw or insufficiently thermally processed;
- pork tapeworm most often affects people in Asia, Latin America and Africa.
The development of a worm is determined by several stages.
- Helminth eggs end up in the environment.
- The intermediate host animal absorbs the grass along with the parasitic eggs.
- A person eating raw or incompletely cooked meat becomes infected with a parasite.
- Helminth larvae enter the human body, which provokes an infectious lesion called teniidosis. At this time, the symptoms of the parasitic presence are usually absent or mild. Among the possible symptoms, diarrhea, constipation or other sluggish disturbances in the gastrointestinal tract are sometimes observed.
- Further, in the human body, the release of larvae from eggs begins. With the help of the intestinal walls, the larvae begin to migrate and enter the bloodstream.
- With the help of blood flow, the larvae are carried throughout the body, deposited in internal organs and tissues. Often it is the muscle fibers, subcutaneous tissues that are affected, and in some cases, organs are also infected.
Swallowing pork tapeworm eggs provokes the development of cysticercosis. The development of this pathology usually does not show any symptoms.
This type of parasite is the smallest representatives of the Tsepney genus. The dwarf tapeworm infects the human body. This worm has individual characteristics, among which the most characteristic is the presence of hooks, their number does not exceed 30 pieces. Adult worms are distinguished by the presence of 3 large testes and a sac-shaped uterus.
Dwarf tapeworms can be active in any part of the world. In most cases, children are infected with this helminth, but infection is sometimes observed in adults. Usually, the defeat of the human body with these parasitic forms is asymptomatic. In some cases, the patient may experience:
- decreased appetite;
- pain in the abdominal region.
Features of the life cycle of a tapeworm of this species:
- Dwarf tapeworm eggs are released into the environment together with feces. Under these conditions, parasites can maintain vital activity for 10 days. They are then swallowed by humans, the ultimate host, or insects, the intermediate hosts. Human infection occurs through dirty hands, water, food.
- The larvae are located in the area of the human small intestine. There they gradually penetrate into the intestinal villi, where they provoke the development of cysticercoids. After the villi rupture, the cysticercoids mix into the intestinal lumen, where they bulge the scolexes and attach to the intestinal wall. This is how the parasites develop into adults.
- Eggs laid by adults are released into the environment with feces.
Parasitic forms of this species choose organisms of fish and birds as intermediate hosts. Wide tapeworms are characterized by the presence of a scolex with two shallow slits that are elongated and located on the back and belly. Proglottids are characterized by dorsoventral flattening from the back to the belly.
Broad tapeworms are the largest tapeworms that can infect the human body. The name of the parasites comes from the peculiarities of their structure. It is interesting that the width of proglottids at any stage of their development exceeds the length of the parasite.
Such helminths are common in many countries, the most common infection occurs in Russia, Switzerland, North America and Finland. This spread is due to the addiction of the inhabitants of these countries to eat not fully cooked poultry and fish.
Broad tapeworms have a complex development cycle.
- Helminth eggs are regularly excreted from the affected organism into the environment along with feces.
- Further eggs develop in freshwater reservoirs. After 6–16 weeks, under favorable environmental conditions, larvae emerge from the eggs. The larva of the broad tapeworm is a six-haired embryo.
- Then the larva is swallowed by freshwater crustaceans, where the parasite develops into a procercoid, which is half a millimeter in size.
- Infected crustaceans serve as food for fish. This is how procercoids enter the muscle tissue of fish and their internal organs. After 3-4 weeks, the larvae form into plerocercoids, which are 4 centimeters long.
- A person eats infected fish, and his body becomes infected with helminths. In the human body, the plerocercoid becomes a mature individual, which is localized in the area of the small intestine.
- Eggs begin to be excreted from the human body along with feces after 4-6 weeks after infection.
The development cycle of tape parasites has a similar structure. Most of them infect the human body with insufficient heat treatment of food. Also, infection is possible with neglect of personal hygiene rules. It is possible to block parasitic cestodes from entering the body, knowing about the developmental cycle of helminths, proper cooking, refusal to eat raw or bleeding meat, as well as careful observance of hygiene standards by adults and children.