Echinococcosis disease: stages. Life Cycle of Echinococcus

Echinococcosis is one of the most severe chronic helminthiasis for humans, caused by a tapeworm of the species Echinococcus granulosus, namely one of its life stages is the larva. From it, in turn, there is such formation as the Finn, which is a bubble, which can reach a sufficiently large size and weigh several kilograms due to the content of liquid in it.

Intermediate and final host

The intermediate owner of this helminth can be not only man, but also cattle, different rodents and other animals. Let us consider in more detail the life cycle of echinococcus. The parasite can begin its development in almost any organ or tissue, but most often this place is the liver and lungs. As a rule, echinococcosis is detected already in the late stages of development, since the first few years there are no clinical signs, which is the main problem of this disease. Sexually mature helminth parasitizes in the intestines of dogs, for example wolves, hyenas, jackals, dogs, so they are his ultimate master.

Brief characteristic of Echinococcus granulosus

First of all, it is necessary to understand what is echinococcus, and also what are the characteristics of its structure. From other representatives of the class it is distinguished by a small size: from 2 to 11 mm - the length of the strobila (chain segments of an adult tapeworm). It also has a cervix, a scolex (head), equipped with a proboscis and a halo of hooks, and four suckers serving to attach to the organ wall. Strobila includes only, as a rule, 3-4 proglottids (joint), of which only the latter contains the yolk, in which up to 800 eggs are formed.

Infection and epidemiology

The person (intermediate host) is infected by the oral route. It is known that the greatest spread of echinococcus occurs in the southern regions. In Australia, a significant number of infections. In addition to the climatic factor, livestock plays a role. So, at least the disease occurs in Kazakhstan, where sheep breeding is widespread. Echinococcosis is affected by people who work in this field of activity, when eating contaminated meat or liver. In addition, you can get sick because of unwashed vegetables and fruits, untreated water, in which viable eggs of echinococcus can appear. Now, for example, in a country like ours, a person can become infected with close contact with dogs, on the wool of which there may be eggs or segments of the parasite after defecation of the animal.

Life Cycle of Echinococcus

Let us consider this question in more detail. The life cycle of echinococcus (the scheme of its development) is simple. It all begins with the fact that the parasite develops in the small intestine of animals belonging to the dog family (dogs, less often wolves). When the individual reaches full maturation, its segments, which are capable of self-movement, come out with the feces of the animal, causing it to have severe itching. At the same time, the segment, which contains a huge number of eggs, bursts. Thus, the eggs of the parasite are in the external environment: on the animal's fur, grass, water, surrounding objects.

It should be noted that the eggs of echinococcus, like other helminths, are resistant to the environment: they tolerate low temperatures, drying out, and their viability, for example, remains in the grass for up to 1.5 months. Thus, the life cycle of echinococcus begins in eggs, which then enter the human body or other animal through water, fruits or unwashed hands. In the infected organism, an invasive stage occurs, a stage of development taking place in a new host. Here from each egg comes a larva named oncosphere, which loses its thick shell and, with the help of its hooks, penetrates through a thin wall into a blood vessel, entering with a current of blood into the liver, then into the lungs. Then, on a large circle of blood circulation, the oncosphere can penetrate into this or that organ, into the muscle or bone tissue.

The new phase

Further, the life cycle of echinococcus enters a new phase, and the oncosphere turns into a Finn. Finn is a fluid-filled bladder containing a large number of scolexes. Here the Finn grows, receiving nutrients from the tissue in which it parasitizes.

Echinococcosis is a disease caused precisely at the final stage of the development of the worm. Echinococcus bladder can be either single-chambered or multi-chambered. In humans, most often the first species that has on the surface smaller bubbles - the daughter. Thus, the echinococcal bladder by its pressure on surrounding tissues disrupts the proper operation of neighboring internal organs and affects the body with secreted toxins.

Also, the bubble can break or start to fester, which is extremely dangerous and can even lead to the death of the patient. In this case, the released scolexes and small bubbles will give an even wider spread of the disease. Only at this stage, because of the size, it becomes possible to identify the disease. In earlier phases, the newest method is used, for which the parasite value-the chaining-does not matter.

For many years, surgical intervention did not lead to a cure, since it breaks the Finns, and then intoxication, which leads to an even more serious, i.e., ubiquitous infection. After considering the life cycle of echinococcus briefly, it is obvious that it continues in the body of the final (primary) host, which becomes infected by eating intermediate meat in which the echinococcal cysts are located.

So, after getting it into the body of the main host, the walls of the bubble dissolve under the action of digestive enzymes, resulting in multiple scolexes being released, and with the help of their two suckers they attach to the mucosa of the intestine. Here the individual becomes sexually mature, which is the end of the life cycle of the helminth. Thus, it is important to understand that if the intermediate owner was a person, then the life cycle of echinococcus finds its development in his body. It becomes a dead end in the cycle of development of echinococcus.

Main clinical signs

Expanding the concept of what is echinococcus, the life cycle, the structure, the scheme of its development, it is important to point out the symptoms of this helminthiasis. It is accepted to distinguish three stages of the disease course, which do not depend on the localization of infection by the parasite. The exact duration of the course of the stages can not be determined due to the slow growth of the echinococcus cyst. It should only be noted that it is the localization of the parasite that is associated with the rate of increase in symptoms. The very first, latent or asymptomatic, stage begins with the penetration of the helminth (invasion of the oncosphere) and lasts until the appearance of the first signs, symptoms of echinococcosis. Characterized by the absence of any complaints of the patient.

Echinococcus cyst is usually found during this period accidentally, for example, in various operations not associated with this parasite, or during preventive examinations. However, sometimes the infected can experience periodic itching, that is, urticaria or other allergic and general toxic reactions indicating an echinococcus whose structure and development life cycle are characterized above.

The next phase

Then follows the so-called stage of the onset of symptoms of the disease, which is characterized by mild signs of parasite infection. Here the echinococcal cyst is already significantly enlarged, it compresses adjacent tissues, which leads to the corresponding symptoms: dyspeptic disorders and, if the infection is localized, for example, in the liver, with periodic blunt drawing pains and liver enlargement (hypatomegalia). So manifests itself in the initial stage of echinococcosis. What is it, the species, the life cycle of this helminthiosis, the prevention of its occurrence - the answers to all these questions are set forth in our article.

Then comes the stage of development of complications, characterized by pronounced objective symptoms, which happens in 10-15% of cases of infection. As already described above, suppuration of the echinococcal bladder (cysts) can occur, its rupture with the ingestion of the contents into hollow adjacent organs or the abdominal cavity. It can also be accompanied by mechanical jaundice arising from the obstruction of the bile duct, portal hypertension and other symptoms that depend on the location of the helminth (lungs, liver, brain). For example, if the parasite has settled in the liver, weight loss, decreased appetite, vomiting, heartburn and belching can be noted.

All this ends with a stage of complicated invasion.

Forms

Having understood what is echinococcus, the disease of echinococcosis, the stage of development of helminthiasis, it is necessary to dwell in more detail on the forms of its manifestation. There are two types of echinococcus: hydatid and alveolar. Gidatidosis often affects the liver and forms a single-chambered bladder. Alveolar, in turn, affects the lungs and has a multi-chambered bladder. The symptomatology of echinococcosis does not depend on the form of the disease: in any case, the helminth develops and exerts pressure on neighboring organs, increasing in size. However, it is known that because of its simpler structure, single-cell cysts are easier to treat. To get rid of a multi-chambered bladder, surgical intervention is required, the success of which directly depends on the degree of cystic enlargement.

Treatment of echinococcosis

Among the main methods of therapy can be identified the following: surgical treatment, antiparasitic and symptomatic therapy. When surgical intervention, the patient is removed echinococcus bubbles, then restore the affected organ or tissue. In this case, a method of radical echinococcectomy is used, in which the cyst is completely removed along with the fibrous membrane.

Sometimes a direct cyst is performed, removing all the fluid and thoroughly disinfecting and cleaning the cavity and previously damaged tissues to avoid repeated, more global infection. In the case of massive organ damage, the operation is not performed. Instead, antiparasitic treatment with special drugs is prescribed. In addition, in the fight against the symptoms of the disease use antihistamines, antitussives and others, depending on the form of echinococcosis.

For 8-10 years after the operation, follow-up at least twice a year is necessary.

Prophylaxis of echinococcosis

Having thoroughly studied what is echinococcus, as well as the symptoms of the development of the disease, it is important to remember that it is easier to prevent an ailment by following recommendations on preventive measures. For this purpose, special veterinary measures are carried out to prevent infection of animals. It is also necessary to pay special attention to people at risk, ie hunters, slaughterhouse workers, livestock keepers and others. As an individual prevention, first of all, you should follow the rules of personal hygiene, drink only from proven sources, thoroughly wash before eating vegetables, fruits and berries, and also limit yourself from contact with stray dogs.