Infective stage for humans of the liver fluke. Invasive stage for humans when infected with opisthorchiasis Pathogenesis, diagnosis and preventive measures

For successful reproduction, the trematode lays up to 40 thousand eggs.

The liver fluke cycle goes through transformations. The sequence of development of the liver fluke: marita – miracidia – sporocysts – redia – circaria – adolescaria.

The liver fluke, in the form of a fertilized marita egg (an adult), along with feces, is excreted from the intestines of the final host (farm animal) into the water. A little more than a month later, the miracidium appears in the egg. From the egg it moves into the water, where it moves with the help of the ciliated cover. The development of miracidium occurs exclusively in the body of an intermediate host - a mollusk (small pond snail Limnaea truncatula). After being eaten by a mollusk, it loses its ciliated cover and becomes a sporocyst.

In a sporocyst with a sac-like structure, redia develop. After leaving the sporocyst, they remain in the liver of the mollusk. In front, the redia has a mouth opening leading to the pharynx and an unpaired food tube. Cercariae form in the redia.

The cercarium is hatched from the mollusk and remains in the water for some time thanks to the tail, which performs a motor function. Once on plants, cercariae change their structure. They are equipped with cystogenic glands that secrete a secretion that envelops the larva and, when solidified, forms a spherical cyst around it, called adolescaria.

Development of helminthiasis

Infection of humans (facultative host) occurs through the nutritional route. In the human stomach, under the influence of gastric juice, adolescaria cysts dissolve, and adolescaria begin to actively move towards the bile ducts. After penetrating through the intestinal walls into the abdominal cavity, the larvae of the liver fluke perforate the liver lining and enter the bile ducts through the liver parenchyma.

Along with established allergic, mechanical and neurogenic factors, infection of the bile ducts plays a major role in the pathogenesis of fascioliasis, especially with long-term progression and complications. The development of acute cholestasis is explained by impaired patency of the common bile duct. In addition, there are pronounced cholangiectasia, sclerosis and atony of the gallbladder.

In liver biopsies in the acute stage of fascioliasis, microscopic signs of abscesses and necrosis with infiltration of eosinophils, lymphocytes, macrophages, and giant cells are observed. The liver fluke takes on a form that is invasive for humans and herbivores only at the stage of development of adolescaria. For the mollusk, the miracidium is the invasive form.

Clinic

The disease can be acute or chronic. It develops in a certain sequence:

Incubation period – acute stage – chronic stage.
The incubation period lasts from 1 week to 2 months.

The main symptoms of the acute stage are the sequentially developing symptoms of intoxication and sensitization. The process begins with a fever of a constant type (the temperature rises to high levels and lasts for several days; daily fluctuations are within 1 degree) or remitting (consecutive significant daily fluctuations of more than 2 degrees) type with chills and myalgia. Fever may last 2–3 months. There are complaints of pain in the epigastrium and right hypochondrium, nausea, and vomiting. Sometimes signs of myocarditis of allergic origin develop.

Signs of diffuse liver damage appear: jaundice, hepatomegaly. The liver feels dense and painful. A characteristic symptom of fascioliasis is an enlargement of the left lobe of the liver, which occurs acutely and is accompanied by severe pain. The duration of the acute and subacute stages of fascioliasis is 2–6 months.

When making a diagnosis, it is necessary to differentiate fascioliasis from the acute phases of other helminthiasis (opisthorchiasis, trichinosis, clonorchiasis), viral hepatitis, leukemia, etc. However, it must be remembered that when eating the liver of an animal affected by the liver fluke, so-called transit eggs appear in the human feces, having passed through the human gastrointestinal tract. The detection of such eggs has no diagnostic value for a given patient. For a final diagnosis, a minimum of two examinations of stool and duodenal contents under a microscope are required with an interval of 1–1.5 weeks.

Laboratory diagnostics

When examining a microscopic specimen of feces or the contents of the duodenum under a microscope, eggs are found to be yellowish-brown, 135*80 microns in size, with a cap at one of the poles. In doubtful cases, a week after the first examination, a repeat examination of the bile is performed, followed by microscopy.

Immunological examination (detection of specific antibodies in blood serum) is highly effective.

A complete blood count shows a significant increase in leukocytes and eosinophils.

In the chronic stage, normal levels of leukocytes or moderate leukocytosis are detected in the blood, eosinophilia is generally insignificant.

When a bacterial infection is added, leukocytosis is detected in the peripheral blood, and ROE increases.

With intrahepatic cholestasis and moderate cytolysis, the level of alkaline phosphatase and transaminases increases. Changes in the protein spectrum of blood serum are observed: hypoproteinemia, hypoalbuminemia.

Treatment regimen

In the acute stage, detoxification therapy is carried out first. Hepatoprotectors, enzymatic, and choleretic drugs are also prescribed.

Therapeutic diet No. 5 is also prescribed.

Antihelminthic drugs are prescribed only after the condition has eased.

Triclabendazole is considered an effective drug. Bithionol is also used in the treatment of fascioliasis.

In the chronic stage of invasion, treatment of cholangitis and biliary dyskinesia is first necessary. If bacterial infections occur, treatment with antibiotics is necessary.

A control examination of stool or bile is carried out 3 and 6 months after the final course of treatment.

Epidemiology

This is a zoonotic invasion. The definitive host and source of infection are herbivorous mammals; the mollusk is only an intermediate host. Human infection is a rare event.

In humid conditions they can survive up to 2 years, but when dried out they quickly die. Distributed in Latin America, Africa, as well as in the South Caucasus and Central Asia (Tajikistan, etc.), Australia, Russia.

Helminthiasis is rare. Small outbreaks of the disease are possible.

Prevention

Types of prevention are divided into personal and public. Actions for personal prevention must be carried out consistently and constantly.

In order to prevent helminthic infestation, it is prohibited to eat unwashed vegetables, berries, and herbs, especially those watered with stagnant water.

To avoid liver damage from this type of helminth, it is recommended to boil raw water from standing reservoirs. In extreme cases, you can filter through a thick cloth.

For the purpose of prevention, the veterinary service should regularly identify and treat sick animals. On private farms, it makes sense to carry out the prevention of liver fluke diseases in livestock. The fight against mollusks in water bodies can also be considered a preventive measure.

It is also important to remember that prevention is always cheaper than treatment.

It is impossible to become infected with fascioliasis by eating shellfish, since they are the intermediate host of the helminth.

Forecast

A timely diagnosis and timely treatment guarantee a favorable prognosis.

After the disease, stable immunity remains.

Attention! Information about drugs and folk remedies is presented for informational purposes only. Under no circumstances should you use the medicine or give it to your loved ones without medical advice! Self-medication and uncontrolled use of drugs are dangerous for the development of complications and side effects! At the first signs of liver disease, you should consult a doctor.

The use of site materials is permitted only with prior approval from the editor.

The skin-muscular sac of flukes includes epithelium and two layers of muscles (Fig. 1). Epithelial cells do not have cilia and are partially buried under the basement membrane. In this case, under the basement membrane there are parts of cells with nuclei, and parts of cells located above the basement membrane merge with each other, forming a nuclear-free cytoplasmic layer - the tegument.

The digestive system begins with the mouth, located at the bottom of the oral sucker. Then there are the sucking pharynx, the esophagus and the intestine, which in most species has two branches. Undigested food remains are eliminated through the mouth.

Excretory system of protonephridial type.

Most flukes are hermaphrodites (with the exception of schistosomes). The male reproductive system includes: paired testes, vas deferens, ejaculatory duct and cirrus (copulatory organ). The ejaculatory duct penetrates the cirrus. The female reproductive system includes: an unpaired ovary, an oviduct extending from it, highly developed vitelline sacs, a spermatic receptacle, shell glands and an ootype. The oviduct, ducts of the vitelline, spermatheca and shell glands flow into the ootype. Fertilization, as a rule, is “cross”: during reproduction, flukes, joining in pairs, exchange male reproductive cells.

rice. 1. Scheme of the structure of the skin

muscle sac of flukes

1 - tegument, 2 - basement membrane,

3 - submerged areas of the cytoplasm

with nuclei, 4 - circular muscles,

5 - longitudinal muscles.

Flukes are characterized by a complex life cycle with a change of hosts and several generations of larval stages. The definitive host is vertebrates. The first intermediate host is necessarily a gastropod. Sexually mature flukes are called marites. The life cycle includes larval stages (sporocysts, redia) capable of reproduction.

The liver fluke, or fasciola (Fasciola hepatica) has a leaf-shaped body, reaches a length of 3–5 cm. The disease causes fascioliasis. The final hosts of the liver fluke are ungulate mammals (horses, sheep, pigs, goats, deer, etc.) and humans. The intermediate host is the freshwater gastropod mollusk small pond snail (Fig. 2).

rice. 2. Life cycle of the liver

1 - marita, 2 - egg, 3 - miracidium,

4 - sporocyst, 5 - redia,

6 - cercaria, 7 - adolescaria.

In the body of the definitive host, fasciola is localized in the bile ducts of the liver. Fertilized eggs pass through the host's bile ducts into the intestines and then through feces into the environment. When released into water, the egg hatches into larvae called miracidium. The miracidium has a ciliated cover, two inverted ocelli, protonephridia, actively searches for an intermediate host (small pond snail) and invades its body. Here the miracidium transforms into a larva - a sporocyst. The sporocyst has a sac-like shape and contains special “germ” cells. From each germ cell in the body of the sporocyst, the following larvae develop - redia. Redia also contains “germ” cells, has a mouth opening, a digestive system, and protonephridia. From the germ cells of the redia, cercariae are formed that have a long tail, two suckers, and a digestive and excretory system. Some scientists consider the method of reproduction of sporocysts and redia to be parthenogenesis, while others consider it a variant of polyembryony.

The stages of the life cycle of Fasciola can be arranged as follows: marita (definitive host) → egg (water) → miracidium (water) → sporocyst (intermediate host) → redia (intermediate host) → cercarium (water) → adolescarium (water).

The invasive stage for humans is also Adolescaria. Human infection occurs by drinking raw water containing adolescaria, or by eating unwashed vegetables and herbs watered with water from reservoirs containing these larvae.

The cat fluke (Opisthorchis felineus) has a lanceolate body shape and reaches a length of 13 mm. Causes the disease opisthorchiasis. The definitive host is representatives of the order Carnivores (foxes, dogs, cats, etc.) and humans. The first intermediate host is the freshwater gastropod Bitinia. The second intermediate host is fish of the Cyprinidae family (roach, carp, ide, etc.) (Fig. 3).

rice. 3. Stages of the life cycle of the cat fluke.

A - the first intermediate host - the mollusk Bitinia, B - the second

intermediate host - fish, 1 - marita, 2 - egg, 3 - sporocyst,

4 - redia, 5 - cercaria, 6 - metacercaria in fish muscles.

The stages of the life cycle can be arranged in the following chain: marita (definitive host) → egg (water) → miracidium (first intermediate host) → sporocyst (first intermediate host) → redia (first intermediate host) → cercaria (water) → metacercaria (second intermediate master).

In the body of the definitive host, the feline fluke marita is localized in the ducts of the liver, gall bladder, and pancreas. For further development, the eggs must fall into the water and be swallowed by the mollusk. In the body of Bithinia, a miracidium emerges from the egg, which transforms into a sporocyst. The sporocyst reproduces to form redia, and the redia reproduce to form cercariae. The cercariae leave the mollusk and enter the body of the fish. In the muscles or subcutaneous tissue of fish, cercariae transform into metacercariae. Metacercaria is the invasive stage for the definitive host.

Human infection occurs when eating poorly fried, poorly cooked, raw or dried fish containing metacercariae. The cat fluke has approximately the same pathogenic effect on the human body as the liver fluke.

The lanceolate fluke (Dicrocoelium lanceatum) causes the disease dicrocoeliasis. The life cycle of this helminth is not associated with water. The definitive host is sheep, humans, etc. The first intermediate host is terrestrial gastropods, the second intermediate host is ants. Life cycle stages: marita (definitive host) → egg (soil, plant surface) → miracidium (first intermediate host) → sporocyst I (first intermediate host) → sporocyst II (first intermediate host) → cercariae in “collective cysts” (soil surface , plants) → metacercaria (second intermediate host). Cercariae, leaving the mollusk, first accumulate in its mantle cavity, secrete a common shell around themselves, forming a “collective cyst”. It is this “cyst” that falls out of the mantle cavity of the mollusk onto the soil or grass, where it is eaten by ants. In the body of ants, cercariae transform into metacercariae.

Human infection occurs through accidental ingestion of ants with metacercariae. Localization and pathogenic action are the same as those of the liver fluke.

The section Bilaterally symmetrical (Bilateria) subkingdom Multicellular also includes:

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Liver fluke: life cycle of development, diagnosis and treatment

According to the classification of Carl Linnaeus, the liver fluke belongs to trematodes (flatworms), which in turn, in addition to the liver fluke, contain several subspecies, the most common of which are the cat fluke, schistosome and pulmonary fluke.

The structure of the liver fluke

Visually, the helminth has the appearance of a narrow leaf; the oblong body of the liver fluke reaches 50 mm in length and 13 mm. 13 in width. On the ventral surface there are two suckers - abdominal and oral, with the help of which the fluke is retained in the host’s body.

The full development cycle of the liver fluke consists of several stages: marites → miracidia → sporocysts → redia → circaria → adolescaria.

Infection of the biliary tract plays a major role in the long-term course and development of complications in the disease fascioliasis. Impaired patency of the biliary tract causes the development of cholestasis. In addition, sclerotic changes in the gallbladder and its atony, as well as severe cholangiectasia, can be observed. In the acute period of fascioliasis, liver biopsy reveals signs of abscesses and necrotic processes. In a form dangerous for animals and humans, helminths are found only at the adolescaria stage. In relation to mollusks, this form is the miracidium.

Main symptoms of fascioliasis

Fascioliasis caused by the liver fluke can occur in acute and chronic forms, each of which has a gradual development:

Symptoms of acute fascioliasis

The latent period of fascioliasis can last from 1 to 8 weeks. The main manifestations of the disease in acute form are the consequences of intoxication and sensitization of the body. There is a constant or debilitating fever. With a constant type of fever, the temperature remains at a high level for a long period, with daily fluctuations not exceeding 1 degree.

For remitting (or relapsing) fever, daily temperature fluctuations of 1.5-2 degrees are typical. Body temperature does not decrease to normal values and may remain elevated for 8-12 weeks. Patients may complain of pain in the epigastric region and right hypochondrium. Nausea and vomiting may occur. The development of myocarditis of allergic origin is possible. Diffuse changes in the liver occur, hepatomegaly and jaundice develop. On palpation examination, the liver is painful and dense. When a liver fluke is present in the body, the symptoms are accompanied by significant pain and an increase in the size of the left hepatic lobe. Subacute and acute stages of fascioliasis can last from 2 to 6 months.

Symptoms of chronic fascioliasis

Modern methods for diagnosing liver fluke

After clarifying the diagnosis, it is extremely important to differentiate fascioliasis. However, we should not forget that when eating animal liver (with insufficient heat treatment) infected with liver fluke, “transit eggs” enter the human body. Their detection is not diagnosed at the initial stage, therefore, to clarify the diagnosis, you need to undergo a double examination of the stool using a microscope. The interval between studies is 1-2 weeks.

Diagnostics in laboratory conditions

Upon careful examination of the stool, and in some cases the contents of the duodenum, specialists discover yellowish-brown eggs, the size of which is 135x80 microns. There are times when the examination has to be repeated.

An immunological study detects specific antibodies in the patient’s blood serum. The doctor prescribes a general blood test, which reveals a significant increase in leukocytes and eosinophils.

In cases where fascioliasis is in the chronic stage, the patient's blood contains a normal number of leukocytes, and eosinophilia is insignificant. If, during an illness, a bacterial infection enters a weakened body, leukocytosis may be detected in the peripheral blood, and the ROE increases. When the disease occurs, a significant increase in the level of alkaline phosphatase occurs, and changes in the protein spectrum occur in the blood serum.

The main methods of treating fascioliasis

In the acute stage of the disease, patients initially undergo detoxification therapy. To relieve symptoms, enzymatic and choleretic medications are prescribed. For the purpose of prevention, the patient is recommended to have a therapeutic diet number five.

When the patient's condition has stabilized, the attending physician prescribes anthelmintic drugs. The most effective of them are triclabendazole and bitinol.

In the chronic form of the disease, biliary dyskinesia is initially treated. When a bacterial infection enters the body, antibiotic treatment is prescribed. The patient should be kept under control until the end of the full course of treatment, after which the doctor will order a stool or bile test. This usually occurs 3 and 6 months after treatment.

Prevention of liver fluke infection

Prevention of liver fluke infection can be of two types: personal and public. For personal prevention purposes, consistent actions should be carried out regularly. To prevent helminthic infestation, it is strictly forbidden to eat unwashed berries, vegetables and fruits. Before eating, they must be thoroughly rinsed under running water.

For preventive purposes, medical examinations of animals should be periodically carried out. Private entrepreneurs engaged in breeding livestock for sale to the public should conduct preventive examinations of animals with the involvement of veterinary workers. Remember that preventive measures will cost much less than treatment. If detected in a timely manner, the disease can be easily treated. After carrying out the necessary procedures, patients develop stable immunity to the development of liver fluke in the body.

Liver fluke: symptoms of presence in humans

How can you become infected with liver fluke?

Infective stage for humans of the liver fluke

and adolescent gynecology

and evidence-based medicine

and medical worker

Type flatworms

Class flukes (Trematodes)

Body coverings and movement apparatus. The body in most cases has a leaf-like shape and sizes from 2 to 80 mm. The body wall of trematodes is made up of a skin-muscular sac. Until recently, it was believed that the body of flukes was covered with a dense cuticle. However, using an electron microscope, it was discovered that their outer cover is a tegument. It consists of a layer of cells fused together so that a total mass of protoplasm (syncytium) is formed. The outer part of the tegument is an anucleate cytoplasm containing a large number of mitochondria. The deep inner part of the tegument contains nuclei. Under the tegument there is a basement membrane, behind which there are smooth muscles, consisting of circular, longitudinal and diagonal muscle fibers.

They have special organs of attachment (fixation) to the host’s body or suckers. Each sucker is a circular muscle with a cavity inside. Usually there are 2 suckers - oral and abdominal. The oral is located at the anterior end of the body, terminally, and is connected to the oral opening, the ventral is on the ventral side and serves only for fixation.

Digestive system. The mouth opening leads to the muscular pharynx, which is a powerful sucking apparatus. The pharynx is followed by the esophagus and usually a branched, blind-ending intestine. The digestive canal opens to the external environment with a single opening - the oral opening, which also serves as the anal opening.

Nervous system consists of a peripharyngeal nerve ring and three pairs of nerve trunks extending from it, of which the lateral ones are better developed. The nerve trunks are interconnected by jumpers. This makes the nervous system resemble a grid.

Excretory system represented by powerfully developed protonephridia. The central excretory canal runs down the middle of the body. Dissimilation is carried out anaerobically, energy is released due to glycogen of parenchyma cells.

Reproductive system reaches exceptional development and is very complex. All trematodes, with the exception of schistosis, are hermaphrodites.

The male reproductive system consists of two compact testes, from each of which vas deferens extend. At the anterior end of the body they connect and form an unpaired compound - the seminal vesicle, which passes into the ejaculatory canal. The distal section of this canal passes inside the copulatory organ - the cirrus. Male reproductive cells are formed in the testes, then enter the cirrus through the vas deferens. When the worms mate, the cirrus bulges outward and is inserted into the vagina of another worm.
The female reproductive system is complex. All its organs are interconnected into a single system. Contains:
- The ootype or central chamber is a small cavity into which the ducts of all organs of the female reproductive system open and where the process of fertilization and egg formation occurs. From the ootype, the eggs move into the uterus and are released through the genital opening.
- The uterus is represented by a narrow tube forming numerous loops. One end of it opens into the ootype, the other ends at the anterior end of the body with the female genital opening next to the opening of the cirrus. In the uterus, the embryo develops in the egg. In addition, in flukes, the uterus simultaneously performs the function of a vagina - through it, male reproductive cells enter the ootype.
- The spermatheca is located next to the ovary and also opens into the ootype. It collects sperm, which subsequently periodically enters the ootype and fertilizes the eggs. In some flukes, fertilization occurs in the spermatic receptacle.
After fertilization, the egg is surrounded by yolk bodies and covered with a dense shell.
Zheltochniki are rounded vesicles located in the lateral parts of the body and opening into ducts into the ootype. In the vitelline cells, yolk-rich cells are formed - vitelline bodies, which are used by the developing embryo.
Melisa corpuscles are small unicellular glands located near the ootype. The liquid secretion secreted by them fills the ootype and, possibly, participates in the formation of the shell (shell) of the egg.
Laurer's canal - extends from the ootype to the dorsal side. It is believed that it serves to remove excess reproductive products.

Fertilization and egg formation. Fertilization, as a rule, is cross-fertilization, i.e., during reproduction, the worms unite in pairs and exchange male reproductive cells. Sperm from the cirrus enter the partner's uterus and pass into the ootype, where they unite with the eggs. The fertilized egg is surrounded by yolk cells, which adhere to its surface, after which a shell is formed on the outside. The formed egg enters the uterus from the ootype and moves towards the external genital opening, while the embryo develops in the egg. The ripe egg comes out through the opening of the uterus.

The egg has characteristic features: its shape is oval, at one pole there is a cap through which the larva emerges.

Life cycle. Flukes are characterized by complex life cycles that include a number of stages. At these stages, sexual reproduction occurs both with and without fertilization, that is, parthenogenetically, which provides a huge number of descendants necessary to maintain the existence of the species.

The final hosts are vertebrates and humans, the intermediate, obligatory hosts are mollusks. Some trematodes, in addition, have a second intermediate host, which can be lower vertebrates and representatives of various groups of invertebrates.

A characteristic feature of the life cycle is the reproduction of larval stages through parthenogenesis.

The sexually mature hermaphroditic stage of flukes is called marita. The body of marita is flattened in the form of a leaf. The mouth is located terminally at the anterior end of the body and is armed with a powerful, muscular sucker. In addition to this sucker, there is another one on the ventral side, which serves to attach to the host’s organs. Marita lays eggs that are carried outside. For further development, the egg, as a rule, must be placed in water.

The first larval stage emerges from the egg - an oval-shaped miracidium, ciliated cover, 2 pigment ocelli at the anterior end of the body and protonephridia. At the back of the miracidium's body are the so-called germ cells, which give rise to the next generation of larval forms. Miracidium floats in water and actively penetrates the body of the mollusk - the intermediate host. Here the miracidium turns into a sac-shaped sporocyst, within which the germ cells are preserved. After some time, from each germ cell inside, sporocysts develop without fertilization, i.e., by parthenogenesis, the next larval stage is redia.
The second larval stage - redia - has an elongated body, pharynx, rudiments of the intestine, nervous and excretory systems and also contains germ cells. The number of redia developing in a sporocyst depends on the type of trematode (from 8 to 100). The redia emerge from the sporocyst into the surrounding tissues of the mollusk. In the body of the redia, the next generation of larvae, cercariae, is also parthenogenetically formed from the germ cells.
Cercariae have a body with a tail appendage, 2 suckers, an intestine, a formed excretory system, and sometimes a rudiment of the reproductive system. At the anterior end of the body, some forms have a sharp stylet or a bunch of spines that perform a perforating function, and a group of penetration glands. Cercariae emerge from the redia and then from the body of the mollusk and float freely in the water.
In most trematodes, the cercariae subsequently penetrates into the second intermediate host (vertebrates, invertebrates) and there they transform into an encysted form - a metacercaria. In those trematodes that have one intermediate host, the cercariae encyst directly in the external environment. This stage is called adolescaria.

Metacercaria and adolescaria are invasive for the final host, in whose body they turn into marita.

Due to the complexity of the development cycle, a significant part of the larval stages of trematodes die before reaching a mature form. Indeed, development will be interrupted if the egg does not get into the water; if the miracidium does not meet a mollusk of the corresponding species or the mollusk is destroyed by other animals; if the cercariae do not meet a definitive host, etc. As a result, only a tiny percentage of larvae reach the marita stage. The above enormous loss is compensated for in two ways: 1) the powerful development of the reproductive system in marita and the production of a huge number of reproductive products (thousands and tens of thousands); 2) reproduction in the stage of larval forms; each sporocyst produces from 8 to 100 redia, each redia, in turn, produces from 20 or more cercariae. As a result, the progeny of one miracidium can be from 600 precercariae.

Trematodes are distributed throughout the globe. The class includes a large number of forms that are pathogenic for humans. Diseases caused by flukes are collectively called trematodes.

Trematodes

Feline or Siberian fluke (Opisthorchis felineus)

. In our country, foci of opisthorchiasis are located along the banks of Siberian rivers, especially the Ob-Irtysh basin. In some settlements of this geographical region, the incidence of opisthorchiasis in the population reaches 100%. Individual outbreaks have been registered in the Baltic states, along the banks of the Kama, Volga, Dnieper and its tributaries, the Southern Bug.

. The cat fluke is a flat, bilaterally symmetrical worm of pale yellow color, 4-13 mm long. At the anterior end there is an oral sucker; somewhat behind it on the ventral side there is a ventral sucker. The outside of the body is covered with a cuticle, under which lie layers of circular, diagonal and longitudinal muscles.

The internal organs are immersed in loose tissue - parenchyma. A muscular pharynx extends from the mouth opening, playing the role of a pump that sucks in food. The short esophagus leads to the midgut, which consists of two branches running along the sides of the body. Excretory organs of protonephridial type. In the back of the body, the excretory “bubble” is clearly visible in the form of a wide winding tube.

The nervous system is represented by a paired head node with trunks extending from it. Two main trunks stretch along the body, and peripheral nerves arise from them.

Opisthorchis is a hermaphrodite. In the middle part of the body there is a branched uterus, followed by a rounded ovary. In the back of the body there are two rosette-shaped testes. The eggs of the cat fluke are x microns in size, yellowish, oval in shape, and have a cap at the front end.

Thus, fish serve as the second intermediate host of opisthorchis. The most common hosts are bream, ide and roach.

Thus, for the first intermediate host the invasive stage is an egg containing a miracidium, for the second it is a cercariae, and for the definitive host it is a metacercariae.

. Opisthorchiasis is a serious disease. With massive infection, opisthorchiasis leads to death. There are known cases where these flukes were found in the human liver. Some patients have liver cancer, the development of which may be, to some extent, provoked by systematic irritation of this organ by flukes. A laboratory diagnosis is made when eggs are detected in feces and duodenal juice. The eggs of the cat fluke are yellowish, oval in shape, tapering towards the pole on which the operculum is located. The second pole of the egg is expanded and has a slight thickening of the shell in the form of a spine.

Prevention. Eat only well-cooked or fried fish, and do not eat fresh frozen or dried fish. With intense salting, metacercariae die within a day. Hot smoking kills the larvae. They do not die during cold smoking. Metacercariae live in frozen fish for 2-3 weeks. Sanitary and educational work is needed aimed at introducing personal prevention measures, which are of primary importance. Public prevention - protecting water bodies from contamination by feces of people with opisthorchiasis.

Liver fluke, or liver fluke, or fasciola (Fasciola hepatica)

Localization. Fasciola is localized in the bile ducts of the liver, gallbladder, and sometimes in the pancreas and other organs.

Morphophysiological features. The body of fasciola is leaf-shaped, 3-5 cm long. In order to distinguish it from other flukes, you should first of all pay attention to the size of the body, as well as the structure of the genital organs. The multilobed uterus is located directly behind the abdominal sucker, behind the uterus, in the anterior third of the body on the right side, lies an unpaired, branched ovary, numerous vitelline cells are located on the sides of the body, and the entire anterior part of the body is occupied by highly branched testes. The eggs are about 135 x 80 µm in size, yellowish-brown, oval; on one pole there is a cap, on the opposite - a tubercle. The intestine has a large number of lateral branching outgrowths.

Life cycle. Fasciola develops with a change of hosts. Its definitive hosts are herbivorous mammals (cattle and small cattle, horses, pigs, rabbits, etc.). Rarely, fasciola is found in humans. The intermediate host is the small pond snail (Galba truncatula).

The Fasciola egg begins to develop only when it gets into the water, where, under favorable conditions, a larva, the miracidium, emerges. Miracidium has a nerve ganglion, a light-sensitive organ “eye”, and excretory organs. In the back part there are germ cells. The anterior end of the body is equipped with a gland that produces an enzyme capable of dissolving living tissue upon penetration into an intermediate host. The miracidium is covered with cilia, thanks to which it actively floats in water. It does not feed, but exists due to the nutrients accumulated in the egg. Inside the body of the miracidium there are special germ cells capable of parthenogenetic development.

Thus, in the life cycle of Fasciola, the invasive (i.e., capable of infecting) stage for the intermediate host is the miracidium. For the definitive host, this stage is adolescaria.

Livestock most often become infested by eating grass in flooded meadows and by drinking water from reservoirs where Adolescaria may be present. People usually become infected through vegetables (usually lettuce) that are watered with water from bodies of water containing adolescaria.

It is interesting to note that in the life cycle of Fasciola there is a free-living stage - the miracidium, which is morphologically close to ciliated worms, which serves as one of the proofs of the origin of flukes from ciliated worms.

Pathogenic significance and diagnosis. Fasciolae, with spines located on the surface of the body and suckers, destroy liver cells, which causes bleeding and degeneration of the tissue of this organ, which can result in the development of cirrhosis. The liver enlarges and becomes lumpy. When the bile ducts are blocked, jaundice appears. The severity of the disease depends on the intensity of the lesion and the individual sensitivity of the patient’s body. Laboratory diagnosis is made based on the presence of Fasciola eggs in feces. They can also be found in the feces of healthy people after eating the liver of animals with fascioliasis (transit eggs). In this regard, when examining for fascioliasis, it is necessary to exclude the liver from the patient’s diet.

Prevention. Knowledge of biological characteristics and life cycle is necessary for organizing control and developing rational preventive measures. A person becomes infected with fascioliasis only by ingesting the invasive stage - adolescaria. This occurs when drinking pond water or eating raw greens from gardens watered with pond water. Because of this, personal preventive measures come down to the following:

do not use raw, unfiltered water for drinking from reservoirs that are dangerous in this regard, and
Thoroughly wash vegetables eaten raw, since greens may contain adolescaria as a result of watering with pond water.

Public prevention measures consist of the destruction of gastropods in water bodies and veterinary measures to deal with fascioliasis in farm animals. To protect livestock from infection, pastures are changed and intermediate hosts are destroyed. To prevent people from becoming infected, sanitary education is of great importance.

Lance-shaped fluke, or lance-shaped fluke (Dicrocoelium lanceatum)

Geographical distribution. Everywhere.

Morphology. The length of the lanceolate fluke is about 10 mm, the body shape is lanceolate. It differs from Fasciola hepatica in the structure of the intestines and reproductive apparatus. The intestine has two unbranched trunks that stretch along the sides of the body to the posterior end, where they end blindly. Two round testes are located behind the ventral sucker. The female apparatus consists of a small rounded ovary located behind the testes, paired vitellines lying on the sides of the body, a spermatic receptacle and a highly developed uterus occupying the posterior part of the body. The eggs of this helminth vary in color from yellowish to dark brown, are oval in shape, and have a small cap on one side.

Life cycle. Development occurs with the change of two intermediate hosts. The definitive hosts are herbivorous mammals. The first intermediate host is terrestrial mollusks of the genera Zebrina, Helicela and some others, the second is ants of the genus Formica.

The eggs of this fluke enter the external environment with the feces of the definitive host. By this time, the already developed miracidium is contained inside the egg membranes. For further development, the egg must be swallowed by the first intermediate host - a terrestrial mollusk. In the digestive tract of the mollusk, the miracidium is released from the egg membranes, penetrates the liver and turns into a first-order sporocyst, in which second-order sporocysts develop. In the latter, cercariae develop, which emerge from the sporocysts and penetrate the respiratory organs of the mollusk, where they encyst, stick together several at a time, forming collective cysts. The latter are released with mucus and fall on the plants.

The second intermediate host, the ant, is invaded by eating prefabricated cysts. Each cercariae, emerging from the shell, turns into the next larval stage - a metacercaria. Metacercariae invade the definitive hosts when ants are ingested along with grass. When the air temperature drops, infected ants move to the tops of plants and fall into a kind of torpor, which facilitates their consumption by their final hosts.

Pathogenic significance and diagnosis. The nature of the course of dicroceliosis is similar to fascioliasis. For the purpose of laboratory diagnosis, feces are examined. At the same time, it is necessary to remember about the possibility of transit eggs entering the human intestine along with the eaten liver of domestic animals suffering from dicroceliosis.

Prevention. Measures to prevent dicroceliosis have not been sufficiently developed. Sometimes ants are controlled in areas where livestock is grazed. However, such measures can lead to other undesirable consequences, since ants are important soil formers and human assistants in the fight against insect pests. The destruction of shellfish and deworming of livestock are also important.

Pulmonary fluke (Paragonimus ringeri)

Geographical distribution. The main focus is some areas of Southeast Asia: China, Korea, Japan, etc. In the USSR, isolated cases have been registered in the Far East.

Localization. Marites live in small branches of the bronchi, causing the formation of cystic cavities.

Morphophysiological characteristics. Characteristic ovoid body shape, red-brown color. Dimensions 7.5-12.0×4-6 mm. The oral sucker is located terminally, the ventral sucker is located approximately in the middle of the ventral side of the body. The intestinal canals are wide, unbranched, and form numerous bends along the way. On the sides of the abdominal sucker lie a lobular ovary on one side and the uterus on the other. The zheltochniki are located in the lateral parts. Several lobed testes are located slightly posterior to the uterus and ovary. The genital opening opens behind the ventral sucker.

Life cycle. Definitive owners are humans, dogs, cats, tiger, leopards, pigs. The first intermediate host is freshwater mollusks of the genus Melania, the second is freshwater crayfish and crabs.

Sexually mature forms live in pairs in bronchial cysts and the laid eggs are released along with sputum into the external environment. Some eggs may be ingested and excreted in the feces. For further development, the egg must be placed in water. The miracidium emerges from the egg and actively penetrates the mollusk, in which the larval stages (sporocysts, redia, cercariae) develop. Cercariae invade river crabs or crayfish, where they transform into metacercariae.

A person becomes infected by eating raw and poorly cooked crayfish and crabs with live metacercariae. Paragonimus emerge from the shell, penetrate through the intestinal wall into the abdominal cavity, and from there through the diaphragm into the pleura and lungs.

Pathogenic effect. In lung tissues, helminths cause inflammation, hemorrhages, and later formation of cystic cavities. Fever, cough with sputum and blood appear, which can simulate tuberculosis. Eggs can be carried through the bloodstream into various organs. Eggs entering the brain are especially dangerous.

Laboratory diagnostics. Detection of helminth eggs in sputum or feces. The eggs are quite large, yellow in color, with a lid.

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Bovine tapeworm is a type of biohelminthiasis, caused by cestodiasis of the Taeniarhynchus saginatus type. You can become infected if you eat meat (in particular beef) without the required heat treatment. The tapeworm that provokes the development of helminthic infestation is a tapeworm.

As mentioned above, the body length of the helminth (as in the photo) can reach up to 12 meters in length. The worm looks like a tapeworm, but has a head, a neck, and segments.

Human tapeworms live in the intestines, where they are attached to the mucous membrane using four suckers. It is these same suckers that help the tapeworm move when it comes out.

Human.
Animal.

You can become infected if you eat a contaminated meat product, provided that the meat contains larvae with embryos. Helminth development cycle:

Tapeworms (as in the photo) have their own incubation period, which lasts up to 100 days. During this period, the small tapeworm turns into a sexually mature adult.

There are many videos about the life cycle of tapeworms that demonstrate the features of their structure, life in and outside the human body.
Signs that bovine tapeworm has settled in the human intestines:

Active segments, through their suction mechanism, contribute to disruption of the functioning of the gastrointestinal tract, resulting in signs of inflammation of the mucous membrane.

The worm, moving through the human body, causes painful spasms, in addition, it is able to suppress the enzyme system.

When a huge number of adult individuals accumulate in the intestines, intestinal obstruction occurs and an acute inflammatory process develops.

Human tapeworms feed quite intensively on useful substances, which leads to a person’s susceptibility to other diseases, bacteria, and so on.

The worm can poison the human body with decay products and toxic substances, resulting in allergic reactions in the form of rashes, eczema, and acne.

Teniarinhoz can be obtained not only by eating meat without proper heat treatment, but also through dirty hands, stale bed linen, and infected household items.

From the intestines, the larvae can penetrate the circulatory system, from there they move to various internal organs, carefully disguised as an intestinal infection, which really complicates and complicates the treatment of bovine tapeworm.

Teniarinhoz is characterized by an asymptomatic initial stage of the disease, and worms can only be detected by taking a stool sample. The danger of the disease lies in the fact that teniarhynchosis becomes chronic, which significantly complicates its course:

Diagnostics

Due to the fact that a person exhibits nonspecific symptoms, it is quite difficult to diagnose the disease. Therefore, an important part is devoted to interviewing the patient.

As a rule, the doctor is interested in the presence of symptoms, even the most minor ones, and asks which family members had helminthic infestations. And only after collecting anamnesis, tests are recommended.

Unfortunately, sometimes the disease is very difficult to cure because the person has not gone to the doctor for a long time, justifying this situation by saying that I am shy. In fact, there is nothing shameful here, and teniarhynchosis is better treated at an early stage.

If a patient suspects that he has a bovine tapeworm, and at the same time, he says, he is embarrassed to tell the doctor about his problem, he needs to familiarize himself with numerous videos that will fully demonstrate what colonies can settle in the human body if they are not gotten rid of in time .

Drug treatment

Biltricide.
Dichlorophen.

Tapeworm in the human body is a serious problem, ignoring which can lead to serious consequences and complications in the future.

The diagram showing the development cycle of the bovine tapeworm illustrates all stages of the disease teniarhynchosis (infection with the bovine tapeworm) from the moment it enters the body until the development of a mature individual capable of reproduction.

The figure shown below is the life cycle of the bovine tapeworm from the body of an intermediate host (cattle) to a permanent host (human).

What is bovine tapeworm

Bull tapeworm belongs to the class of tapeworms. The length of these helminths can range from 3 to 12 meters. The tapeworm has a small head (scolex), on which there are four suckers, with the help of which it is “fixed” on the intestinal walls.

The tapeworm is a hermaphrodite. Its structure is as follows:

scolex (head about 3-4 mm in size) with four suckers;
neck of the worm;
a body consisting of segments, the number of which can reach several thousand.

Bovine tapeworm develops in the human body for about 3 months until the formation of finn, which then comes out along with feces.

Methods of infection

The main method of infection is eating meat with helminth larvae that is not cooked correctly. Infection can occur if people consume raw or insufficiently cooked food.

The cut of meat contaminated with bovine tapeworm larvae shown in the photo makes it possible to avoid purchasing such a product at a spontaneous market, where the meat is unlikely to have passed the appropriate veterinary control.

But there are several more ways you can become infected with bovine tapeworm:

dirty hands;
bed and underwear of a sick person;
personal hygiene items, towels (especially for intimate hygiene);
eating unwashed berries and fruits.

The human small intestine is the “kingdom” of the bovine tapeworm, where it settles and causes irreparable harm to the body, the consequences of which very often become irreversible:

The earlier the worm is detected in the body, the more successful the treatment will be. Symptoms of bovine tapeworm are:

sudden mood swings, irritability, stress, depression;
wandering abdominal pain, the location of which can change every few minutes;
the occurrence of allergic reactions even in people who have not suffered from allergies until this moment;
change in taste preferences, fluctuations in appetite. There may be either a complete absence of it or an excessive desire to eat (“zhor”).

Methods for diagnosing and treating bovine tapeworm

Among the diagnostic methods there will certainly be the following:

fecal analysis for the presence of tapeworm eggs that are already coming out;
complete blood count - the number of red and white blood cells will be significantly reduced;
gastroscopy with examination of gastric juice. In the presence of helminths, acidity decreases;
X-ray of the intestine using contrast - the mucous membrane will be smoothed, the presence of small erosions is possible.

Anamnesis that looks like this indicates the presence of teniarynchosis, which must be treated immediately.

Treatment includes three main stages, on compliance with which the success of treatment depends:

preparatory – lasts approximately two weeks. During this period, the body is cleansed of toxins that the tapeworm releases during its life. Sorbents are used, for example Enterosgel. They can be replaced with pumpkin or flaxseed oil. They need to be drunk 1 tsp. before each meal;

restorative measures for the whole body - diet, vitamin complexes and herbal medicine to strengthen the immune system and restore the functioning of the gastrointestinal tract.

The bovine tapeworm is the most dangerous among helminths. The threat is posed not only by its size and duration of “residence” in the host’s body, but by the latent early period of progression, which makes treatment more difficult and lengthy.

Pathogenic effect. Clinical manifestations vary greatly. Many organs of the patient are involved in the pathological process. In children, the disease is acute. Inflammatory processes develop in the bite area, lymph nodes, liver, and spleen enlarge. Encephalitis and meningoencephalitis may develop. In adults, the disease is chronic and most often affects the heart muscle and central nervous system.

Source of infection- sick people and reservoir animals (armadillos, opossums, rodents, dogs, cats and some species of monkeys).

Prevention: a) public - improving social living conditions and preventing bedbugs from entering a person’s home; b) personal - protection from bedbug bites.

Leishmania tropica - Leishmania tropica- the causative agent of cutaneous leishmaniasis, Borovsky's disease, known in the CIS under the name "Pendinsky ulcer" - anthropozoonosis.

Countries of South Asia, North Africa and some areas of Southern Europe; in the CIS, the disease is most common in Turkmenistan and Uzbekistan.

Localization- skin cells.

There are several species and subspecies of Leishmania.

1. Leishmania tropica minor is the causative agent of the urban, chronic, dry form of skin leishmaniasis.

2.L.t. major is the causative agent of rural, acute, wet form of cutaneous leishmaniasis. 3. L brasiliensis - the causative agent of cutaneous leishmaniasis in the Western Hemisphere, etc. Their structure is similar. In the human body and reservoir animals, Leishmania develops intracellularly, forming a leishmanial, tissue (amastigote, flagellate) form. These are oval or round non-motile cells, from 2.8 - 6 µm in length and 1.2 - 4 µm in width. Inside, the centrally located nucleus and the kinetoplast are clearly visible. Motile, flagellated leptomonad (promastigote) forms are formed in the body of mosquito carriers, as well as in cultures on a nutrient medium. The cells are spindle-shaped, 10-20 µm long, 5-6 µm thick, with a nucleus located in the center, a kinetoplast and a free flagellum directed forward at the anterior end of the body.

Development cycle

Invasive form- promastigote. Leishmania enters human skin cells through the bite of mosquitoes of the genus Phlebotomus. In skin cells they turn into the amastigote form.

Pathogenic effect. Itchy ulcers form on the skin. The urban form has a long incubation period, up to six months. The slowly growing bump on the skin begins to ulcerate after 6 months. The ulcer is dry and usually affects the face. Scarring occurs on average after a year. The rural form has an incubation period from 2 weeks to 3 months. The disease begins acutely. The tubercle on the skin quickly ulcerates; weeping ulcers occur most often on the extremities. After 1-2 months they heal.

Source of infection- a sick person and reservoir animals (small rodents, gophers, hamsters, sometimes rats and dogs).

Prevention: a) public - sanitary and educational work; identification and treatment of patients; measures aimed at combating mosquitoes and destroying natural reservoirs - rodents around populated areas within a radius of 1-2 km; preventive vaccinations are used; b) personal - individual protection against mosquito bites (covering windows with nets, sleeping curtains).

Leishmania donovani- the causative agent of visceral leishmaniasis, which exists in several forms: Indian kala-azar, Mediterranean childhood leishmaniasis, East African leishmaniasis, etc. All geographical variants of the disease are anthropozoonoses.

Geographical distribution- Indian kala-azar - India, Pakistan, Nepal, China; Mediterranean childhood leishmaniasis - north-west China, Middle East, Latin America, Central Asia, Transcaucasia; East African - Sudan, Kenya, Ethiopia, Somalia and Uganda.

Localization- Leishmania affects cells of the reticuloendothelial system (spleen, liver, bone marrow, lymph nodes and gastrointestinal tract).

Morphological characteristics. Similar in structure to L. tropica.

Malarial plasmodia: plasmodium vivax, p. malariae, p. falciparum, p. ovale- pathogens of three-day, four-day, tropical and oval malaria - anthroponoses.

Geographical distribution- everywhere, especially often in countries with tropical and subtropical climates.

Localization- liver cells, red blood cells, endothelium of blood vessels.

Morphological characteristics. There are:

1. Sporozoites - formed in the stomach of a mosquito of the genus Anopheles in an amount of about 10,000 from one oocyst, penetrate the hemolymph and then into the salivary glands of the mosquito. This is the stage that is invasive to humans. Sporozoites are spindle-shaped, 11-15 µm long and 1.5 µm wide, motile.

2. Tissue trophozoites - round in shape, 60 -70 microns in diameter, located inside hepatocytes.

3. Tissue merozoites - elongated, 2.5 µm long and 1.5 µm wide, emerge from hepatocytes into the blood plasma.

9. Mature schizonts - endoerythrocytic stage. The schizont shares schizogony. Merozoites are formed inside the schizont. Depending on the species, they reach a certain number in one schizon (8-24). In P. vivax -12 -18, in P. malariae 6 -12, in P. falciparum 12 -24, in P. ovale 4 -12.

11. Mature gametes - are formed in the stomach of a mosquito from gametocytes. The macrogametocyte increases in size and turns into a macrogamete. Division and exflagellation (maturation) occur in the microgametocyte, resulting in the formation of 4 to 8 motile, rope-like microgametes.

12. Ookinete - formed from the zygote after copulation of macro- and microgametes, has an elongated shape and is capable of movement.

13. Oocyst - formed from an ookinete under the outer lining of the mosquito’s stomach. The oocyst is round, covered with a capsule, immobile.

14. Hypnozoites - found only in the developmental cycle of P. vivax and P. ovale. They are localized in liver cells, are capable of long-term persistence and cause relapses of the disease.

In the body of a new host, for example, cysts of dysenteric amoeba, sporozoites of falciparum plasmodium, eggs and fins of pork tapeworm.

1. Small medical encyclopedia. - M.: Medical encyclopedia. 1991-96 2. First aid. - M.: Great Russian Encyclopedia. 1994 3. Encyclopedic Dictionary of Medical Terms. - M.: Soviet Encyclopedia. - 1982-1984.

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