Life cycle of bovine tapeworm. The structure of a bull chain

Parasites are an important health problem in many countries. Band worms infect people around the world. The most common of these are bovine and pork thistle. As adults, these worms live in the intestine and usually do not do much harm. But if people become infected with cysts (immature stage), then cysticercosis can develop - a disease that can lead to brain damage.

What is a parasite?

A parasite is an organism that lives inside the host organism and at its expense. Viruses are the smallest of all infectious agents, they average about 100 nanometers (100 billionths of a meter) in length. They have so few genes and protein of their own that in order to produce offspring, they need to invade another's cell structure. Bacteria vary widely in size and shape, but tend to be at least 10 times greater than viruses. They are single-celled organisms that reproduce themselves. Multicellular parasites can be so large that they can be seen with the naked eye. Tape worms, for example, can reach 6 meters or more in length. Food and water are the most common sources of transmission of parasites. Since most of us eat three meals a day and drink water throughout the day, the influence of these sources is constant. Animals, like humans, can get infected by parasites. And they are the main carriers of parasites. Experts believe that of the 110 million domestic dogs and cats in our country, more than half can be infected with at least one or more types of parasites. Given these data, the potential for transmission of parasitic infections from animals to humans is extremely high. Parasites are classified by structure, form, function and reproductive capacity. These include microscopic organisms, roundworms, pinworms and worms (nematodes), tapeworms (cestodes) and flukes (trematodes).

History of the discovery

Bovine tapeworm is considered one of the earliest human parasites. To tapeworms it began to be attributed in the late 1700s. However, the exact life cycle of the bull's chain was examined in detail in 1863, when the cattle were directly identified as the direct owner.

Morphology and bovine tapeworm: photo

The parasite has the form of a long, flattened, ribbon-like chain in white. Its diameter is about 6 to 7 millimeters. An adult worm, as a rule, has about 1000 segments, called proglottids. In contrast to the scolex with 4 suckers, this is a relatively harmless body of a bull's eye. Each proglottid contains both male and female reproductive organs, through which eggs are produced with embryos, each of which has a size of 31-43 micrometers. The incubation period takes 5 to 12 weeks.

Conditions for the successful completion of the life cycle

The life cycle of a bovine chain includes one or more intermediate hosts. The distinctive morphological and physiological properties of the adult parasite reflect, on the one hand, their striking ability to survive in the intestines of vertebrates, and on the other, their ability to reproduce offspring. The life cycle of bovine chain is complicated and has a number of essential conditions for successful completion:

1. Proglottids filled with eggs enter the environment through feces.

2. These "pregnant" segments penetrate the body of cattle eating the infected vegetation, so they enter the digestive tract of the intermediate host. Enzymes and acids, which are contained in gastrointestinal juice, break down the protective barrier and release up to 100,000 eggs.

3. Eggs develop into larvae, which break through the epithelium of the intestine and travel through the body of cattle. Then the larvae enter the muscular tissue, their oncosphere is filled with liquid, forming cysts.

4. To complete the complex life cycle of a bull tart (the diagram clearly shows this), contaminated, undercooked beef meat should be eaten by a person (the final master) to get into his digestive system. Digestive enzymes break the membrane, the larvae are released, and the inverted scolex is able to exit the capsule. Then it is attached to the intestinal wall. After that the parasite starts to grow and within three months can reach 5 meters in length. At this point in maturity, he is already capable of releasing proglottids to resume the life cycle of the bovine tapeworm.

Life Cycle Scheme

The dimensions of the parasite in the adult stage are usually colossal and range from 4.5 to 9 meters. The worm bovine tapeworm lives in the small intestine. An infected person usually has only one or two individuals. To attach to the intestinal wall, tapeworms use their head, which is called scolex. They have from 1,000 to 2,000 body segments, called proglottids, each containing 80,000 to 100,000 eggs that can survive for months or years in the environment. When cattle eat up contaminated larvae, eggs enter through their intestinal walls looking for peculiar holes in muscles and remain there in the form of a fluid-filled cyst that is a protective capsule for them. If people eat raw or half-baked beef, containing cysts, cysts develop in adult tapeworms for 2 months. An adult bovine tapeworm can live more than 30 years.

Classification

Tape worms, including bovine tapeworm (see photo in the review), belong to the class of cestodes. This is a group of parasitic flatworms, which includes about 5000 species. Tape worms are found all over the world and have a range of sizes from 1 mm to more than 15 m. They are internal parasites of individual species of invertebrates and all kinds of vertebrates, including humans, domestic animals. Some worms exist separately, others require one or more intermediate hosts during their life cycle. The structure of a bull chain, like other tapeworms, assumes bilateral symmetry (i.e., the right and left sides are identical). Some consist of one long segment, others have a prominent head, followed by a series of identical segments, called proglottids.

The body of the chain

The body of the bovine chain is represented in the form of a tape, flattened both from the top down and bilaterally (symmetrically). It is characterized by the presence of three embryonic leaves (ectoderm, mesoderm and endoderm), the respiratory and circulatory systems are not developed. The body is covered with a rigid and simultaneously flexible cuticle, there are also no cardiovascular and respiratory systems, but there is a bilateral nervous system. Even large tapeworms consist almost entirely of reproductive structures with a small "head" for attachment. Adult individuals usually have the same body structure. The latter consists of scolex, cervix and a large number of proglottids, which are sometimes called segments. The neck of the chain is a clearly defined, short, narrow and un-segmented area behind the scolex. It consists of a relatively undifferentiated mass of cells. This is the zone of growth and expansion of the segmentation area, since it is here that new proglottids are formed. The structure of the bovine chain also includes nerve rings and lateral nerve endings that extend along the entire length of the body. Pre-digested in the small intestine food is the main source of food for the chain. The overall surface area of the parasite is significantly increased due to the presence of microvilli.

Reproduction

Like any other, the life cycle of a bull's chain has its main task to continue its kind. Tape worms are hermaphrodites, since they contain both male and female genital organs in one organism, and male maturation comes first, therefore the anterior part of mature proglottids consists only of male genital organs. Thus, they are a full-fledged reproductive unit that produces eggs either by self-fertilization or cross-fertilization with other mature proglottids. After that, a detachment from the rest of the body occurs. This phenomenon serves to limit the length of the parasite. The developing embryo comes out with the stool of the host.

Signs, symptoms and diagnosis of infection

Infection with a bull chain is accompanied only by mild symptoms, including diarrhea, constipation, flatulence, abdominal pain and weight loss. How do doctors diagnose and treat the infection? Eggs and proglottids can be seen in feces samples during microscopic examination. To accurately determine that the tapeworm is bovine or porcine, it is necessary to remove and study their scolexes. This is rarely done, since doctors usually prescribe the same medicines for both types of infection. Larvae of helminths in the cysts of tissues tissues can be detected using the method of radiography, as well as computed tomography (cysts of the brain). Control is also performed at 3 and 6 months after treatment to ensure that the infection has gone completely.

Bovine tapeworm causes shadowiarinosis

The bovine tapeworm belonging to the group of tapeworms is a fairly large specimen that causes an infection called shadowarhynchosis. He got his name because he uses cows as intermediate hosts. People are only final carriers. The disease often occurs asymptomatically. In a severe stage, it can sometimes cause inflammation of the appendix and bile ducts. Infection can also compromise the immune system. Especially deep impact of the consequences of infection can have on the health of young children. Teniarinhoz is found everywhere and is relatively common in Africa, Eastern Europe, Latin America and the Philippines.

Treatment

Treatment is traditionally carried out with special medications. This is, as a rule, "Fenasal", "Prazikvantel", "Nichlosamide." Endoscopic treatment is the introduction of the drug directly into the small intestine. This causes the parasite to come out completely naturally.

Prevention

Tape worms can cause intestinal diseases and other severe pathologies. Infestation by bulbar can be prevented by careful preparation of meat, this serves as a guarantee that any cysts of the chain are destroyed. Alternatively, you can freeze the meat and hold it at a temperature below -5 ° C for several days. Prevention of infection of cattle is also food in those areas where vegetation can not be contaminated by human feces. A reliable method of preventing endemic distribution is the detection of infected cattle. It is also important to follow the rules of hygiene and maintain cleanliness, which involves regular hand washing, especially after going to the toilet. Adequate sanitation is the key to eliminating the infection around the world.