Bovine tapeworm message on biology. Stages of development of the bovine tapeworm

Bull tapeworm is also called unarmed tapeworm. This is due to the fact that there are no hooks on the head of the worm, while the pork (armed) tapeworm has them. The bovine tapeworm is attached to the intestinal walls only by suckers. The word "tape" comes from the word "chain". The body of the worm consists of individual segments, which makes it somewhat similar to a chain.

Intermediate host is the cattle in which the larvae develop bovine tapeworm.

Taeniarinhoz is most common in those areas where people eat poorly cooked beef (Latin America, Africa, etc.).

The structure of the bull tapeworm

By external structure The body of an adult tapeworm consists of a head ( scolex), neck and many segments ( proglottid). New segments form in the cervical area. As you move away from it, larger and more mature proglottids are found. “Maturity” is determined by the maturation of the eggs in the segment. At the posterior end of the worm, the proglottids break off and exit the intestines along with the feces or simply crawl out.

The body length of an adult bull tapeworm varies greatly. Can reach more than 10 m, but usually less. The length of mature segments is about 2 cm. The number of segments is more than 1000. One individual lives about 18 years.

On the scolex there are 4 suckers without hooks.

Internal structure bovine tapeworm is in many ways characteristic of flatworms: a skin-muscular sac, parenchymal tissue instead of body cavities, absence of blood and respiratory systems, hermaphroditic reproductive system, the presence of an excretory system consisting of protonephridia. However, tapeworms are characterized by the absence of an intestine and mouth opening, i.e., a general absence of a digestive system.

The worm's body is covered tegument, in which the outer cytoplasmic layer has projections, due to which food is absorbed. Since the adult bovine tapeworm lives in the small intestine, where food has already been digested, then digestive system in fact he doesn't need it.

The life cycle of the bovine tapeworm includes a change of two hosts (humans and cattle) and consists of the following stages: egg → larva I ( oncosphere) → larva II ( Finn) → adult.

The detached segment ends up outside, where it can crawl and disperse its eggs containing oncospheres.

If an egg enters the digestive tract of, for example, a cow, then the larval stage of the bovine tapeworm, the oncosphere, already formed in the egg, comes out of it. It is equipped with hooks, with the help of which it drills through the intestinal wall and enters the cow’s circulatory or lymphatic system. Oncospheres are carried with the blood to the muscles and connective tissues host animal. Here the oncosphere turns into Finn (Finnish). It can be considered the second larval stage of the bovine tapeworm.

A Finn cow can live for many years in its body.

If a person eats uncooked beef meat containing finca, then the heads of a young bovine tapeworm unfold in his intestines. They adhere to the intestinal wall, begin to feed and form segments.

Each segment (proglottid) of the bovine tapeworm includes male and female genital organs. The head (scolex) is located in the center in the photo

History of discovery

Morphology

Proglottids. The strobila consists of a chain of proglottids (segments), which are mainly filled with eggs. New proglottids are produced at the neck and this growth pushes the more mature segments towards the posterior end, where they break off and thus release thousands of eggs. This process is very important in the complex life cycle of this tapeworm. The bovine tapeworm is the largest human helminth of its kind, consisting of 1,000 to 2,000 segments, which can remain viable in the human intestine for up to 25 years.

Scolex. The scolex of the bovine tapeworm has a diameter of 1.5 - 2 mm and consists of four suckers at the anterior end of the flatworm, which are used as a means of attachment to the intestinal wall of the host. The bovine tapeworm lacks hooks on the scolex, unlike its close relative the pork tapeworm, which infects domestic pigs and then humans. The eggs of both types of tapeworms are indistinguishable. They have a round or oval shape, covered on top with a thin (approximately 31-43 microns), colorless shell.

The egg contains the larval form (oncosphere) of T. saginata, surrounded by a double-edged yellowish-brown shell, which is destroyed after the eggs are released. The oncosphere has 6 hooks.

Life cycle

1. Mature, egg-filled segments (proglottids), located in the intestines of the final host (human), are excreted into environment along with feces. Each such segment contains up to 100 thousand eggs, which already contain infective larvae.
2. These proglottids are able to move through the grass and soil for some time, spreading eggs, which are then absorbed by large horned cattle (cattle) along with contaminated vegetation and enter the gastrointestinal tract of their intermediate host.
3. Enzymes and intestinal acids destroy the egg shell and release oncospheres (larvae), which, damaging the intestinal epithelium, can be transported through the bloodstream throughout the body of the cattle. After this, the larvae penetrate into muscle tissue, the oncosphere fills with liquid and turns into a fin (cysticercus).
4. To complete the complex developmental cycle, raw or poorly cooked beef must be eaten by a person (the definitive host) and then enter the human digestive system. Digestive enzymes destroy the cysticerci, the larval cysts are released, and their inverted scolex is able to come out and attach to the walls of the host’s intestine.
5. Next, the maturation of adult individuals occurs, during which the head and neck begin to grow rapidly, producing more and more new proglottids. The bull tapeworm increases in size, and within three months it can reach a length of up to 5 meters. After maturation, mature egg-containing proglottids separate from the tapeworm, and the life cycle restarts.

Routes of infection

Bovine tapeworms enter the human body by consuming raw or undercooked beef. On average, 2-3 months pass from the moment of infection to the formation of a sexually mature individual. Helminths can maintain their vital activity in the body of the definitive host for up to 25 years.

Cases of the disease are more common in adults than in children, which is explained by dietary habits. It is also noted that people working in meat processing plants, slaughterhouses or in various food establishments (cooks) suffer from teniarinhoz more often than others.

Geographical distribution

Signs and symptoms

Most people infected with bovine tapeworm do not experience any symptoms unless the tapeworm grows quite large. In such situations, a person may experience a feeling of fullness, and sometimes (rarely) even nausea to the point of vomiting. The worm or worms can rarely cause acute intestinal obstruction, and individual proglottids can block the lumen of the worm, causing acute appendicitis.

In addition, with teniarynchosis the following may be observed:

• loss of appetite;
• weight loss;
• headache;
• general weakness;
• itching in the anus.

Often patients become aware of the infection by finding a proglottid (or large segment of the worm) in the stool during bowel movements. These proglottids sometimes crawl down the thighs, usually when a person is active, and produce a tickling sensation.

Elevated levels of eosinophils and immunoglobulin E (IgE) may also indicate the presence of infection.

It should be noted that a significant difference between pork and bovine tapeworms is that the cysticercus stage does not occur in humans with T. saginata when eggs are ingested. Therefore, infection with a bovine tapeworm is less dangerous than with a pork one, since in the latter case cysticerci can enter the central nervous system, eyes and other organs, developing into small subcutaneous cysts. Then they talk about cysticercosis.

Treatment and prevention

As with most cestodes, treatment involves the use of. Niclosamide is also effective in this situation.

Among the folk methods of getting rid of worms, the most popular are pumpkin seeds and garlic-milk mixture.

The body (strobilus) of a tapeworm has a ribbon-like shape. Consists of individual segments - proglottids. At the anterior end of the body there is a head (scolex), followed by an unsegmented neck. On the head there are attachment organs - suckers, hooks, suction slits (bothria).

Diseases caused by tapeworms are called cestodiases.

Bovine tapeworm (Taeniarhynchus saginatus) is the causative agent of taeniarynchosis. There are only 4 suction cups on the head.

The final host of the bovine tapeworm is only humans, intermediate hosts are cattle. Animals become infected by eating grass, hay and other food with proglottids, which, along with feces, get there from humans. In the stomach of livestock, oncospheres emerge from the eggs, which settle in the muscles of the animals, forming fins. They are called cysticerci. A cysticercus is a fluid-filled sac with a head with suction cups screwed into it. Finns can be preserved in the muscles of livestock for many years.

Able to actively crawl out of the anus one by one.

A person becomes infected by eating raw or half-raw meat from an infected animal. In the stomach, under the influence of the acidic environment of gastric juice, the shell of the finna dissolves, and the larva emerges and attaches to the intestinal wall.

The effect on the host is:

1) the effect of food withdrawal;

3) imbalance of intestinal microflora (dysbacteriosis);

4) impaired absorption and synthesis of vitamins;

5) mechanical irritation of the intestines;

6) possible development of intestinal obstruction;

7) inflammation of the intestinal wall.

Prevention.

1. Personal. Thorough heat treatment of meat.

2. Public. Strict supervision over the processing and sale of meat. Carrying out sanitary education work with the population.

44. Dwarf pork tapeworm

Porcine, or armed, tapeworm (Taenia solium) is the causative agent of taeniasis. The final owner is only human. Intermediate hosts are pigs and, occasionally, humans. The segments are excreted in human feces in groups of 5–6 pieces. When the eggs dry out, their shell bursts and the eggs scatter freely. Flies and birds also contribute to this process.

Pigs become infected by eating sewage, which may contain proglottids. The egg shell dissolves in the stomach of pigs, and six-hooked oncospheres emerge from it. Through the blood vessels they enter the muscles, where they settle and after 2 months turn into fins. They are called cysticerci and are a bubble filled with liquid, inside of which a head with suction cups is screwed.

Human infection occurs when eating raw or insufficiently heat-treated pork. Under the influence of digestive juices, the cysticercus membrane dissolves; The scolex is everted and attached to the wall of the small intestine.

With this disease, reverse intestinal motility and vomiting occur quite often. In this case, mature segments enter the stomach and are digested there under the influence of gastric juice. The released oncospheres enter the intestinal vessels and are carried through the bloodstream to organs and tissues. They can enter the liver, brain, lungs, eyes, where cysticerci form.

Treatment of cysticercosis is only surgical.

Diagnostics. Detection of mature segments in the patient's feces.

Prevention.

1. Personal. Thorough heat treatment of pork.

2. Public. Pasture protection - strict supervision over the processing and sale of meat.

The dwarf tapeworm (Hymenolepis nana) is the causative agent of hymenolepidosis. The head is pear-shaped, has 4 suckers and a proboscis with a corolla of hooks. The strobila contains 200 or more segments; only eggs enter the environment. Egg size is up to 40 microns. They are colorless and have a round shape.

Man is both an intermediate and a final host. Oncospheres penetrate into the villi of the small intestine, where cysticercoids develop from them. Young individuals attach to the intestinal mucosa and reach sexual maturity.

Pathogenic effect. The processes of parietal digestion are disrupted. The body is poisoned by the waste products of the helminth. Intestinal activity is disrupted, abdominal pain, diarrhea, headaches, irritability, weakness, and fatigue appear.

Diagnostics. Detection of dwarf tapeworm eggs in the feces of a patient.

Prevention.

1. Compliance with personal hygiene rules.

2. Public. Thorough cleaning of child care facilities.

Figure: development and structure of the bovine tapeworm

Features of the structure of the bovine tapeworm

Bovine tapeworm nutrition

Reproduction of the bovine tapeworm

Like most other flatworms, tapeworms are hermaphrodites. In each of its segments, except for the youngest, there is one ovary and many testes. The eggs mature only in the oldest, posterior segments. These segments break off and come out with feces.

Bovine tapeworm development

Cattle can ingest tapeworm eggs in grass. In the stomach of the animal, microscopic larvae with hooks emerge from the eggs. With their help, the larvae burrow into the wall of the stomach, enter the bloodstream, spread throughout the animal’s body and penetrate the muscles. Here the six-hooked larva grows and turns into Finnish- a pea-sized bubble, inside of which there is a tapeworm head with a neck.
In undercooked or undercooked meat, tapeworm larvae are kept alive. If a person eats such meat, he becomes infected with it. Bovine tapeworm secretes toxic substances, which cause intestinal disorders and anemia in humans.