The pygmy chain is the causative agent of hymenolepidosis

Among the numerous intestinal parasites of humans, the dwarf tapeworm or Hymenolepis is known for its particular infectiousness and tenacity, since – unlike most other helminths, in particular nematodes – it is able to reproduce in the human body, and it is not so easy to cleanse the intestines of this flatworm.

The causative agent of hymenolepiasis, according to the taxonomic status accepted in parasitology, belongs to the type Plathtlminthes, class Cestoidea (tapeworms), subclass Cestoda (cestodes), order Cyclophyllidea (cyclophyllides), family Hymenolepididae (hymenolepidids).

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Structure of the dwarf tapeworm

Describing the structure of the dwarf tapeworm, parasitologists note that its morphology is no different from the structure of other representatives of the class of tapeworms - intestinal anaerobic parasites of vertebrates.

The length of the body of an adult, i.e. ready for reproduction, dwarf tapeworm does not exceed 40-50 mm, and the width is 1 mm. The body of the parasite is a strobila - a chain of two to three hundred repeating segments or segments (proglottids). Also in the front part of each worm there is a scolex (head) and a neck. The scolex of the dwarf tapeworm has four bothria (slit-like suckers), and between them - a retractable rostellum (proboscis), "armed" along the entire upper edge with about three dozen hooks. Thanks to this "equipment" the tapeworm easily attaches to the mucous membrane of the small intestine. Here, in the scolex, is the main nerve center (ganglion), from which sensory and chemoreceptor nerve cords extend along the entire strobila.

Immediately after the scolex comes the neck of the worm, during the growth of which new proglottids are separated. That is, the maturing segments are gradually pushed to the end of the chain by the younger ones. Moreover, each segment feeds independently and has its own hermaphroditic reproductive system, which works hard. And by the time the mature proglottid reaches the end of the worm's body, it becomes a sac filled with eggs. Then the segment simply detaches from the worm's body and, having fulfilled its function, collapses, releasing the eggs.

The eggs of the dwarf tapeworm (0.03-0.05 mm in diameter) are covered with a thin hyaline membrane on the outside and have a thickened internal membrane. Each egg contains a hooked embryo of the larva (oncosphere) with a diameter of up to 0.015-0.018 mm.

The dwarf tapeworm has no digestive system, and ready-made nutrients from the host's small intestine are simply absorbed by the cells of the worm's tegument - a multilayered surface tissue (7-15 µm thick) consisting of syncytium (multinuclear tissue), distal cytoplasm (containing plasma membranes), glycocalyx (a layer of carbohydrate-containing macromolecules), and proximal cytoplasm (the inner layer that contains nuclei, endoplasmic reticulum, mitochondria, ribosomes, etc.).

The inner layer of the surface tissue of the dwarf tapeworm strobila is limited by the basal plate, under which are muscle fibers that provide the body with the ability to move. Nature took into account that the nutrition of this type of cestodes occurs through endocytolysis, therefore the release of metabolic products occurs through special cells - protonephridia.

By the way, it has been established that the complete dependence on the host, in whose intestines this parasite settles, is connected with its inability to synthesize lipids. Moreover, lipids are necessary for the dwarf tapeworm and other cyclophyllides not as a source of energy, but exclusively for strobilation - asexual reproduction.

Life cycle of the dwarf tapeworm

In the vast majority of cases, the life cycle of the dwarf tapeworm, which lasts approximately 30-45 days, occurs in one organism.

The causative agent of hymenolepiasis enters the body of a healthy person in the form of eggs, which come out of the intestines of an infected person with feces. Outside the host's body, eggs with oncospheres do not remain viable for long, but this time is enough for some of them to "settle" inside another host. The intermediate host of the dwarf tapeworm is a person in whose intestines the hymenolepis undergoes an intermediate stage of its development. And a person in whose intestines this worm reproduces is the definitive or final host of the dwarf tapeworm.

In the mouth of a person (and then in the intestines) the parasite eggs can end up together with food products on which flies (mechanical carriers of any helminths) have sat, with contaminated water, from unwashed hands, from dishes, in general, from any objects. If the habitat of adult tapeworms is the upper sections of the small intestine, then the eggs may not get into the feces, and then constant self-infection occurs. So the routes of infection with dwarf tapeworm, in the first case, are fecal-oral, and in the second - autoinvasive. Children are especially often infected with hymenolepiasis.

In the intestine of the final host - under the action of digestive enzymes - the hyaline membrane of the cestode eggs dissolves, and the embryo of the larva is released. Then comes the invasive stage of the dwarf tapeworm, during which the oncosphere with its hooks clings to the mucous membrane of the small intestine (to the loose tissue at the base of the intestinal villi) and within a few days the finna of the dwarf tapeworm or cysticercoid is formed. For some time the finna matures until the appearance of a scolex buried in the body and a body with a tail appendage.

But when the intestinal stage begins, the cysticercoid loses its tail appendage, straightens the scolex, leaves its "familiar" place and bites into new intestinal villi to get more nutrients and develop further. After two weeks, the mature segments of the strobila of the dwarf tapeworm are filled with eggs, and everything starts anew.

Symptoms of Dwarf Tapeworm

The symptoms of dwarf tapeworm, or more precisely, the symptoms of hymenolepiasis, are related to the fact that both adult worms and their larvae damage a large number of intestinal villi with their suckers and hooks - outgrowths covering the entire mucous membrane of the small intestine walls. This leads to ulceration and necrosis of not only the border epithelium of the villi, but also to damage to the deeper layers of the intestinal walls and intestinal capillary vessels. In this case, general malaise, abdominal pain (sometimes intense), diarrhea or constipation, mucous-bloody particles in the feces are noted. Due to disturbances in the intestinal microflora, the digestion process is also disrupted, causing nausea, vomiting, heartburn and belching.

Moreover, due to damage to the lymphatic and blood capillaries inside the villi by the parasite, the flow of proteins, lipids and carbohydrates necessary for the body into the bloodstream is disrupted. And dwarf tapeworm in a child (in addition to nausea and pain in the abdominal cavity) often leads to dizziness, fainting, loss of appetite and body weight, anemia, decreased activity, and sleep problems.

The metabolic products of the dwarf tapeworm lead to general intoxication of the body, which manifests itself in convulsions, deterioration of the ability to remember, increased nervousness, etc.

Parasitic invasion also causes allergic reactions, since the human immune system (in the intestines, these are lymphoid follicles and Peyer's patches) cannot help but react to foreign protein as an antigen. As a result, when infected with this helminth, skin rashes, conjunctival inflammation, and allergic rhinitis can be observed.

Diagnosis of dwarf tapeworm

Considering the non-specificity of the symptoms of hymenolepiasis and the fact that in a third of cases the symptoms are practically not manifested, the diagnosis of dwarf tapeworm is carried out on the basis of coproovoscopy - a laboratory analysis of feces for the presence of eggs of this type of tapeworm. Moreover, the analysis is taken three times - every 14 days (which is associated with the life cycle of the parasite).

An enzyme immunoassay of blood (for the presence of antibodies) may also be required. And in severe cases of invasion, hardware diagnostics are used - ultrasound or CT of the intestines and abdominal organs.

Treatment of dwarf tapeworm

In order to completely expel the parasite from the small intestine, treatment for dwarf tapeworm should be prescribed by a doctor, since in some cases the course of taking anthelmintic drugs must be repeated repeatedly - with a control stool test.

The most commonly used drugs against dwarf tapeworm are Phenasal (other trade names are Niclosamide, Niclosamide, Yomesan, Cestocide, Devermin, Gelmiantin, Lintex) or Biltricide (synonyms Praziquantel, Azinox, Cesol).

Phenasal (in 0.25 g tablets) does not enter the bloodstream from the gastrointestinal tract and acts directly on the parasite, disrupting its intracellular metabolism, which leads to the death of the worm.

The tablets are supposed to be taken 4 times a day; the daily dose for adults and children over 12 years is 8-12 tablets (2-3 g). If a dwarf tapeworm is detected in a child aged 5-12 years, then 6 tablets (1.5 g) are prescribed during the day, 2-5 years - 4 tablets (1 g). A child under two years old needs 2 tablets (0.5 g). The tablets are chewed or crushed, mixed with a small amount of water, and drunk an hour before meals, and then every two hours. The first course of treatment lasts 4 days, and after a 4-day break, a second course of taking Phenasal is carried out. Coproovoscopy is mandatory exactly two weeks after the second course.

Treatment of dwarf tapeworm is also carried out with Biltricide (available in 0.6 g tablets). This drug paralyzes intestinal parasites, and they fall off the intestinal mucosa. Tablets are taken orally after meals (without chewing and with water). The dose is calculated depending on body weight and age (20-60 mg / kg). The intake can be either single (before bedtime) or multiple - at 5-hour intervals. Biltricide is contraindicated for children under 4 years old, pregnant and lactating women, and side effects of the drug are nausea, vomiting, diarrhea, headache, increased drowsiness and lethargy; blood pressure and temperature may temporarily increase, and a rash may appear on the skin.

Treatment of dwarf tapeworm with folk remedies

Parasitologists, for obvious reasons, are quite skeptical about treating dwarf tapeworm with folk remedies. For example, advice to do garlic enemas, or eat more sauerkraut or hot peppers...

However, some folk methods have a right to exist. Such phytotherapeutic means include decoctions of wormwood or tansy. An infusion of tansy flowers is prepared at the rate of 10 g (a teaspoon) per glass of boiling water. In large doses, the plant is poisonous, so this decoction can only be taken by adults - a sip three times a day half an hour before meals.

Wormwood decoction (a dessert spoon of dry plant per 250 ml of water) is recommended to drink 60 ml three times a day. But the greatest antihelminthic effect will be achieved by using wormwood powder, which is very easy to prepare from a dry plant using an electric coffee grinder. This powder should be taken by teaspoon 4-5 times a day, mixed with honey or washed down with a small amount of water.

Herbalists advise preparing a powder from three ingredients at once: dry wormwood herb, tansy flowers, and the culinary spice cloves (taken in equal quantities).

The phenolic compound eugenol, which is abundant in cloves, has biocidal properties. And tansy contains monoterpine (thujone), which stimulates intestinal peristalsis, which is most likely why it is famous as a powerful remedy for fighting pinworms and roundworms.

Prevention of dwarf tapeworm

Prevention of dwarf tapeworm is possible and necessary. The main preventive measure is clean hands, eating only thoroughly washed fruits and vegetables, and identifying patients with hymenolepiasis and treating them.

The eggs of the dwarf tapeworm can only be neutralized by treating the dishes (in kindergartens, in the public catering system) with boiling water. The dishes should be stored dry and in closed cabinets - so that flies do not sit on them, which have no place in the kitchen of a kindergarten, or in a cafe, or in an apartment.

Vegetables and fruits can be kept in hot water (+65-70°C) for 10-15 minutes, or washed well in running water, allowed to drain, and then put in the refrigerator for 40-45 minutes (with a temperature no higher than -3-4°C).

And patients with hymenolepiasis must be identified and treated. And when going on holiday to countries with a hot climate, you should be especially careful and observe the rules of personal hygiene. For example, in Egypt, 22% of children aged 5 to 16 are found to have dwarf tapeworm, which leads to anemia and a deficiency of vitamins B9 and B12 in the body.