Hepatic fluke development cycle

Cycles of development of flukes are characterized by a change of owners. Hosts in which mature worms parasitize are called final. The hosts in which the larval stages of the fluke develop intermediate. In addition, in the development cycle of some flukes, there may be additional hosts containing the last larval stage of the development of the parasitic worm. The final host becomes infected by eating only last stage worm development.

Hepatic fluke development cycle

Liver fluke, or Fasciola parasitizes in the bile ducts of the liver of cattle, small cattle and other herbivorous mammals. The body is leaf-shaped, gray-white, size 2-5 cm. EggsLiver fluke enter the environment along with the excrement of the final host. For further development, the eggs must necessarily fall into a fresh water reservoir. In the water, a larva with cilia leaves the egg miracidium. Miracidium swims for a while, then finds an intermediate host for a freshwater gastropod mollusk Small pond and is actively being introduced into his liver. In the liver of a mollusk, miracidium turns into the following larval stage - sporocyst. Further, each sporocyst turns into numerous larvae of the next generation - radium and redia in cercariae. Cercariae have a stylet, they break through the body of the mollusk and go into the water. For some time, cercariae swim in the water, then attach to the near-water vegetation, become covered with a thick shell and turn into adolescari. Cattle, going to a watering place, eats grass with adolescari attached to it. In the intestines of the final host, the membrane of adolescari dissolves, and young Liver fluke penetrates the liver. Thus, ingestion of adolescari is the only way to infect the final host. It is necessary to treat animals with fascioliasis in order to exclude egg ingress. Fasciola into the environment.

Cycle of development of the Lanceolate fluke

Lanceolate fluke, or Dicrocelium parasitizes in the bile ducts of the liver of cattle, small cattle and other herbivorous mammals. The body is leaf-shaped, gray-white, size 0.5-1.2 cm. Eggs flukes enter the environment along with the excrement of the final host. The eggs already contain miracidia. Eggs must be swallowed by land gastropods Helicella, Zebrina or Chondrilloy. In the liver of these intermediate hosts, each miracidium turns into sporocyst sporocyst turns into numerous radium and redia in cercariae. Cercariae slip into the mucous lumps and fall through the respiratory opening of the mollusk onto the grass. These mucous lumps are sweet in taste and ants from the genus eat them with pleasure Mirmika. In the brain of an ant cercaria turns into metacercariae. Metacercaria, localized in the ant’s brain, causes a change in the ant’s behavior: the ant crawls on tall blades of grass and freezes in a motionless position. Cattle on a pasture swallows ants along with grass. In the intestines of the final host, metacercariae turns into an adult trematode and penetrates the liver of its host. In order to prevent infection of livestock with dicrocellosis, it is necessary to treat sick animals, thus excluding the ingestion of eggs of fluke into the environment.

Feline Fluke Development Cycle

Cat fluke, or Opisthorchis, parasitizes in the bile ducts of the human liver, dogs, cats and other carnivorous mammals. The body of the trematode is leaf-shaped, gray-white, size 0.7-1.2 cm. Into the environment the eggs flukes get along with the excrement of the final host. For further development, the eggs must necessarily fall into a fresh water reservoir. An egg that already contains miracidia to be swallowed by an intermediate host by a freshwater gastropod Bitinia. In the liver Bitinia every miracidium turns into sporocyst then the sporocyst turns into numerous larvae of the next generation radium and redia in cercariae. Cercariae have a stylet with which they break through the body of the mollusk and enter the water. Cecaria swim for some time in the water, find some cyprinid fish (carp, common carp, bream, crucian carp), through the covers of fish cercaria actively penetrate into the muscles of the fish, where they turn into a larva of the last age - in metacercariae. The final hosts become infected with a fluke by eating raw carp fish. In order for a person to avoid infection with opisthorchiasis, heat treatment of fish is necessary, in addition, salted fish, cold smoked fish and planer should not be consumed.

The development cycle of giant hepatic and hepatic hepatic

Adult worms parasitize in the biliary system of humans or animals, secreting eggs that enter the environment along with the feces of the final host.

When eggs fall into fresh water, larvae (miracidia) emerge from them. They penetrate the body of gastropods, where they are transformed into sporocysts, and then into cercaria. After 2 months, cercariae leave the body of the intermediate host and again fall into the water. Here they turn into adolescari, these larvae are ready for invasion of the final host. It is in this state that they attach to the water film, or to the surfaces of plants.

After getting into the digestive tract of an animal or human, the larvae penetrate through the walls of the stomach into the abdominal cavity. There they find the liver, invade its parenchyma, reaching the bile ducts.

Sometimes the larvae migrate through the circulatory system, reaching the bile ducts through the portal and intestinal veins. For 3-4 months, the larvae mature in the bile ducts, after which they begin to secrete eggs into the external environment.

Liver and giant fluke can parasitize in the human body for 10 or more years.

The development cycle of hepatic trematode causing opisthorchiasis

With the feces of the final host, which is an animal or human, the eggs of the parasites go into the external environment and enter the reservoir. There they are swallowed by freshwater mollusks, in the body of which the larvae undergo certain changes and turn into cercariae. Two months later, the parasite leaves the mollusk and independently penetrates the body of fish. Larvae of worms prefer fish of the carp family.

In the body of the fish, cercaria throws off its tail and becomes mobile, transforming into metacercaria. Already after six weeks from being in the body of the fish, the face becomes invasive.

After it enters the stomach and upper part of the small intestine of a permanent host (human or animal), the larva penetrates the gallbladder and the liver. The parasite will reach puberty in two weeks. Trematodes can exist in the human body from 10 to 30 years, eating red blood cells, epithelial cells and mucus secreted by the biliary tract.

Development cycle of a lanceolate fluke

In the body of a permanent host (human or animal), a mature parasite parasitizes, which, together with feces, secretes eggs to the external environment. They enter the soil and are swallowed by land mollusks. In their body, cercaria is formed, which goes into the external environment.

Cercariae is eaten by ants and is transformed into metacercaria in their body. After this, the ants become infectious. When the larvae enter the digestive tract (swallowed together with ants), they penetrate the bile ducts and the gall bladder of the final host, mature there and begin to secrete eggs into the external environment.

Who is the intermediate host for hepatic trematode?

The gastropod mollusks are an intermediate host of the hepatic trematode, namely, the giant and hepatic hepatic flukes. Most often it is a pond of the genus Galba. They live in large numbers in stagnant bodies of water, where the water warms up well. These may be low-lying swampy meadows and pastures. It is interesting that in Australia there are no mollusks of the species Lamnea truncaltula, however, hepatic trematode is quite widespread. The parasite was introduced into the continent with domestic animals and managed to find a new intermediate host - the mollusk L. Tomentosa.

Inside the mollusks, the larvae become sporocysts, and then the stages of caudate cercariae grow. In the body of gastropods, the liver fluke spends 1 to 2 months.

Hepatic trematode, provoking opisthorchiasis, requires a change of two intermediate hosts. The first of these is a freshwater mollusk of the genus Bithynia inflate, and the second intermediate host is fish from the cyprinid family (ide, roach, tench, top, etc.).

The intermediate host of the lanceolate fluke are terrestrial mollusks, and after them - ants.

Education: In 2008, a diploma was obtained in the specialty “General Medicine (General Medicine)” at the N. I. Pirogov Russian Medical Research University. An internship was immediately passed and a therapist diploma was received.

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Life cycle

The parasite begins its development in contaminated water bodies. The cycle of existence of the hepatic trematode is divided into the following stages of development:

  1. Starting with an egg that has fallen into water, the fluke develops for about 3 weeks.
  2. At the end of time, miracidium emerges from the eggs - the fluke larva. In this state, the parasite does not need food. During its existence in water, it leads a free-living lifestyle. During this period, the body reaches about 0.3 mm in size and begins to move at a speed of 2 mm per second. The ability to move appears due to cilia on the body. At this stage, the parasite has the only goal - to find the body in which it will continue its life.
  3. The search for an intermediate host begins. Such for the hepatic trematode is a mollusk. Once in it, the parasite continues its growth cycle. During this period, miracidium is converted into a sporocyst. In this form, his path continues.
  4. The sporocyst accumulates germ cells in itself and proceeds to a new stage - redia.
  5. Reds enter the mollusk's liver and begin to multiply. For this, fertilization is not required at this stage. Then the parasites are converted to cercaria.
  6. Cercariae are adults. They begin to move freely, exist due to the accumulated useful substances. After a certain period, cercaria migrate to the soil and grass adjacent to the reservoir. At this moment, they discard their tail.
  7. A new stage of the parasite is adolescaria. To continue the life cycle, the parasite at this stage must find the main host, which is affected through raw water or unwashed food. In the human body, it lays eggs that go out with feces, and the cycle starts anew when a change of owners occurs.

The development scheme is quite complicated. But, nevertheless, a person is not safe from the disease, although it is more characteristic of cattle.

Symptoms of the presence of fluke

The disease has a medical term - fascioliasis. Hepatic trematode is a source of infectious processes in the liver. The liver channel is clogged, which negatively affects the work of blood vessels. The primary stages of the disease are characterized by such signs:

  • a strong increase in body temperature,
  • violation of the respiratory system,
  • diarrhea or constipation
  • rashes and redness on the skin,
  • pain in the liver.

If the fluke develops in the human body for a rather long time, then the symptoms become more serious:

  • acute pain not only in the liver, but also in the pancreas,
  • severe colic in the abdomen
  • imbalance
  • severe and frequent migraines
  • fatigue, rapid fatigue of the body,
  • the appearance of a cyst on the organs.

Important to remember! When the liver is affected by this parasite, it increases in size! Concomitant organ diseases may develop. Therefore, timely treatment is very important for health.

Diagnostics

The diagnosis of this disease at an early stage of development can be established presumably, since the life cycle did not have time to reach its end. Therefore, eggs cannot be detected - they have not yet appeared. To clarify the diagnosis, you should take an analysis of feces several times with an interval of 1 week. Then the result will be more understandable for a specialist.

The most effective method for diagnosing this disease is an immunological study. It helps detect atypical antibodies in serum.

Important! A comprehensive study of feces and blood will help the doctor diagnose much faster! Timely detection of the parasite will help the favorable conduct of therapy.

Disease treatment

If you treat the disease on time, then you can get rid of complications such as acute peritonitis and liver tumor. To combat the hepatic trematode, a comprehensive treatment is carried out:

  1. Preparations against parasites. They directly affect the source of the disease, ensuring the rapid death of parasites in the body. Such drugs can be: Chloxyl, Vermox, Praziquantel and their analogues.
  2. Cholagogue medicines. Contribute to the removal of parasites from the body. Medicines of this group: Allohol, Cholenzym, as well as drugs with an identical composition.
  3. Enzymes that help restore the body. You can take: Festal, Mezim, Pancreatin.

Without fail, all medications should be prescribed by a specialist.

It is important to know! Ignoring the hepatic trematode in the body can lead to unpleasant consequences, even death! Therefore, an important point is the timely and productive disposal of this type of parasite.

Aloe vera and onion

Take the same amount of these components, mix. Add 1 tbsp. l honey, consume 3 times a day for 1 tbsp. l

It will take 1 tbsp. l tansy, which you need to pour 0.5 liters of water and simmer for about 10 minutes. The resulting broth should be filtered and applied in the form of an enema every day.

Important! Before using traditional medicine, you should consult a specialist so as not to harm your health!

Complications

Liver trematode can spread to many vital organs. So, parasites affect the lungs, brain, mammary glands, subcutaneous tissue. Treatment of complications is a very complex and long-term process.

Also, in rare cases, liver cirrhosis and chronic cholecystitis may develop. Therefore, the timely detection of fascioliasis will help to avoid fatal consequences.

Disease prevention

An important condition for preventive measures is their constancy. You should add these rules to your habit:

  • wash vegetables, fruits and herbs with boiled water before eating,
  • raw water must be boiled before use,
  • should be heat treated meat offal.

Subject to all precautions and prophylaxis, the risk of contracting a hepatic trematode is minimal.

The structure and development cycle of helminth

The hepatic trematode is a fairly large worm, which is a hermaphrodite. In width, it reaches 13 mm, and in length - 30 mm (rarely - 50). You can clearly see the parasite under a microscope (see photo).

The structure of the worm is quite simple:

  • head end in the form of a trunk with spikes and a suction cup (digestive system of the fluke),
  • extra abdominal suction cup,
  • dense multilayer cuticle (protection against bile).

Two helminth suction cups help him stay in place. The worm lays a large number of eggs, which are transferred into the intestine by the flow of bile, and from there into the external environment.

The life cycle of helminth development takes place in the form of alternation of the following stages:

The stages of development of the helminth are difficult and depend on 2 hosts - the intermediate (mollusk small pond) and the latter (herbivore). The intermediate host is a carrier of hepatic parasite larvae.

The worm cyst and a mature individual (hermaphrodite) contains the main host, in the body of which the cyst and individual are formed.

The development of hepatic trematode:

  1. Cysts enter the body of a pet. From the external environment (more often: when watering from rivers or lakes and eating coastal plants), the cyst by ingestion enters the body of a cow, sheep, pig, etc. In the digestive organs (intestines), a sexually mature parasite leaves the cyst, which travels to the liver and ducts.
  2. Fertilization and egg formation. The hepatic trematode is a hermaphrodite, that is, an adult individual fertilizes itself. The eggs exit the genital tract of the helminth, enter the intestines, and then are excreted into the external environment along with feces.
  3. Larva. The fluke egg must get into the pond in order to turn into a larva, and in the body of the mollusk - a small pond, go through the stages of its development. From an egg in the aquatic environment, a larva with cilia is first released. It is they who enter the mollusk body, where it develops and propagates asexually to other larvae, including those that have a tail.
  4. The formation of cysts. A larva with a tail gets to plants near a reservoir, attaches to it, surrounding itself with a high-density shell - this is a cyst, which then enters the body of a herbivore.

After this, the pattern is repeated first. The lifespan of a mature worm in the body of an animal or person is up to 5 years.

Infection of a person with hepatic hepatic flux with an incubation period of 1 to 8 weeks causes the development of a pathology such as fascioliasis.

Infection pathways

A liver fluke (cat fluke) can be infected from pets (cats). Many owners often offer cats raw fish (bream, dace, rudd, roach, carp), which often contains helminth eggs.

A person can become infected by the fecal-oral and contact route: by accidentally swallowing raw water from a reservoir, using poorly heat-treated fish or meat products, through unwashed hands, from another person, in contact with soil containing feces, non-observance of sanitary hygiene rules, eating infected animal liver with helminths, poorly washed greens from the garden, poor processing of kitchen tools, knives, cutting boards after cleaning products.

Infection with a fluke can:

  • people with special preferences in national cuisine where they eat raw foods,
  • fishermen
  • hunters
  • sellers
  • farm workers
  • children playing with land or sand.

Most likely, helminth infection will occur in a person who is irrationally eating, has weak immunity, chronic diseases and frequent stresses.

Symptoms of helminthiasis

Hepatic trematode causes the development of fascioliasis. The disease is characterized by the appearance of high fever, abdominal pain and right hypochondrium, signs of skin allergy, shortness of breath, tachycardia.

Quite often, there are also signs such as: slight yellowness of the skin, mucous membranes, enlarged liver, general malaise, aching joints, pain in the muscles, digestive tract problems (diarrhea, constipation, heartburn, nausea, unpleasant sensations in the stomach) . Choking may occur.

The disease can occur in complicated and uncomplicated forms. Actively develops chronic fatigue syndrome. The body weight of a person is reduced, and the state of the immune system is significantly worsened. In addition, causeless irritability appears, insomnia, and then headaches join. And as a result, human performance decreases.

The clinical picture is very difficult, because by common signs, infection with the hepatic trematode is very similar to other parasitic (and even viral) diseases. Therefore, proper diagnosis and qualified medical care are very important.

The fluke is dangerous for the human body because it causes pathological processes in the liver, clogs the ducts and negatively affects the blood vessels. A large blood vessel passes through the liver, from which the helminth takes away useful substances, and into it the worm gives off toxic substances formed as a result of parasitic activity.


Blood with toxins negatively affects the general condition of the body and the well-being of a person, since it does not contain in sufficient quantities the necessary trace elements and vitamins. The oxygen content is reduced. Nutrients in large quantities are absorbed by the hepatic trematode.

In addition, worms can clog the biliary tract, obstruct the outflow of bile, causing the development of diseases of the digestive tract in the human body.

Cirrhosis of the liver, caused by the presence of cat fluke, often leads to death. In addition, an infected person may develop biliary (or acute abdominal) peritonitis, purulent cholangitis, and malignant neoplasms.

Diagnostic methods

The detection of infection by the hepatic trematode is carried out according to the generally accepted scheme:

  1. History taking.
  2. Examination of the patient.
  3. Laboratory studies (feces and duodenal contents on helminth eggs, blood tests - general and ELISA).
  4. The use of instrumental methods (ultrasound, MRI, CT, pancreatocholangiography).

Accidental detection of helminth eggs in feces is not yet a fact of infection (this happens with the use of an animal’s liver). It will be necessary to repeat the analysis after 1 week with a vegetarian diet. Then the doctor allows you to eat as usual.

If a person suspects that he might have been infected with helminths, it is necessary not to delay the visit to the clinic, and quickly begin the examination. Early diagnosis allows you to stop the disease in the early stages.

Read more about methods for diagnosing helminthiases in the article http://otparazitoff.ru/glisty/diagnostika-gelmintozov.html

Infection treatment

It is advisable to get rid of the hepatic trematode as soon as possible in order to prevent large hepatic lesions. A doctor (parasitologist, therapist) prescribes drugs for helminths (Praziquantel, Chloxyl), choleretic (Allochol, Cholenzyme), antihistamines (Fenkarol, Calcium chloride) and drugs that positively affect the digestive tract (Festal, Mezim, Enzistal).

In addition, symptomatic therapy is prescribed, which fights against manifestations of allergies, inflammation, signs of chronic diseases that increase immunity and fortify the body. Sometimes antibiotics are prescribed, as well as corticosteroids (Prednisone).

With the development of complications (for example, purulent cholecystocholangitis, liver abscesses), surgery and the rest of the complex therapy are performed. Also, patients are recommended protein-vitamin nutrition and iron preparations. Herbal medicine (anthelminthic fees), the use of pumpkin seeds also helps.

With a timely medical course, the prognosis of the disease is favorable. The entire drug course should be prescribed by a doctor.

How not to get infected with a liver fluke?

In order not to become infected with a parasite, a number of rules must be followed. First of all, you need to observe personal hygiene (wash hands with soap after working in the garden, coming from the street, toilet), clean the house.

It is necessary to heat fish and meat semi-finished products well. In the kitchen, have different cutting boards that need to be carefully processed after each use. Do not drink raw water. On vacation or swimming in natural springs, you should be careful and try not to swallow water from rivers or lakes.

Observing all the rules of prevention, you can avoid infection by the hepatic trematode and maintain health. It will be necessary to get rid of the cat fluke for a long time, therefore it is better to follow preventive measures and not be afraid of helminthic invasion.

Video material about the fasciola life cycle:

First intermediate host

Where does the parasite live? It depends on the stage of development. Any fasciol chooses, as a first intermediate host, a mollusk, freshwater or land. Its specific appearance depends on the variety of the parasite itself. The larvae hatching from the eggs must invade the mollusk body within a few days or die if this is not possible. The lanceolate fluke is distinguished by the fact that snails swallow its eggs, and the larvae of them hatch already in their gastrointestinal tract.

In the body of the mollusk, the larva successively passes through several stages of “maturation”. She then leaves the intermediate host to find another. This happens on average after 2-3 months.

Second intermediate host

Fourth generation larvae swim freely until they meet the next intermediate host. Most often it is a freshwater fish. From liver flukes are particularly affected:

Having penetrated the muscle tissue, the larva becomes covered with a dense shell and falls into a kind of “suspended animation”. It comes out of hibernation when the gastric juice of a person or a mammal who has eaten fish that has not undergone a sufficiently lengthy heat treatment (raw, frozen, dried, slightly salted) dissolves the “capsule”. This is how infection occurs.

From the stomach with a blood stream, the parasite gets to where it originally sought - in the liver or bile ducts. What does fasciola eat? Blood and bile.

Larval stages

The life cycle of the hepatic trematode involves several transformations. From the embryo to the adult, the following stages of development of the hepatic trematode are successively changing. Reproduction occurs by parthenogenesis. The morphology of the hepatic trematode is rather primitive in comparison with the complexity of development.

  • Miracidium. Oval larva covered with “cilia” to help stay afloat. It possesses the rudiments of internal organs and two “eyes” (sensory organs) capable of perceiving light. The posterior end of the body consists of cells that begin to divide intensively when the first intermediate host enters the body.
  • Sporocyst. A kind of "bag" with an oral cavity. Inside - germ cells, which are preserved in the next stage.
  • Redia. The larva already has the rudiments of the gastric, excretory and nervous systems. The body lengthens, the oral cavity and pharynx are clearly outlined. From one sporocyst, depending on the type of hepatic trematode, 10 to 100 redia develops.
  • Cercarius. The presence of a “tail”, dorsal fins (organs of movement), and suction cups in the oral cavity is characteristic. Also at the front end of the body there is an acute “awl” (like a swordfish) for penetration into the body of a second intermediate host. The cercaria leaves the body of the mollusk and swims in the water, purposefully conducting an appropriate search.
  • Metacercariae. It is formed when the cercaria finds its target and “pupates”, being covered with a dense shell. The larva is in a passive state until it enters the digestive system of the final host.
  • Marita. A sexually mature hermaphrodite, capable of reproduction. The reproductive system of the hepatic trematode is the testes and unpaired ovary, concentrated on the "dull" end of the body. The body shape is leaf-shaped, the worm itself is almost flat. The oral cavity and abdomen are equipped with a powerful suction cup. The intestine in the hepatic trematode is absent. These are ideal adaptations to parasitism, allowing you to gain a foothold in the liver after traveling through the ducts of the vessels that surround it. The structure of the hepatic trematode is quite primitive. Excretory system - the outer integument.

The stages of the life cycle of the hepatic trematode are replaced by one another only when certain conditions are met. At any stage, “failures” are possible, leading to the death of eggs or larvae. This can explain the extraordinary fertility of the helminth and the preservation of the ability to reproduce throughout the entire period of life.

Liver flukes Are parasitic worms belonging to the type Flatworms. There are many types of liver flukes. Usually in the educational literature under this name the type of hepatic fluke is described.

The life cycle of the hepatic trematode is complex. It includes two hosts: the final (vertebrate herbivore) and the intermediate (mollusk small pond). In a vertebrate animal, sexual flux occurs, which is why such a host is considered final. Reproduction occurs in the cochlea, but it is asexual and proceeds at the larval stage. The life cycle of the hepatic trematode includes several larval stages.

If you describe the life cycle in multiple ways, then it looks like this:

Hepatic trematode cysts are swallowed by domestic animals (cows, sheep, etc.). This usually happens at a watering place, where animals not only drink, but also eat coastal grass, to which cysts attach.

In the digestive tract, an adult worm comes out of the cyst. They call her marita. It penetrates the bile ducts of the liver and parasitizes there, feeding on blood and tissues. Marita hepatic trematode has two suckers - oral and abdominal. They hold the worm. At the bottom of the oral sucker is the mouth. The structure of the hepatic trematode is similar to that of the white planaria. However, the adult fluke does not have cilia on the epithelium. His body is covered with a protective shell - tegument.

The hepatic trematode is a hermaphrodite. Cross fertilization (two worms fertilize each other). Sexually transmitted parasite the eggs enter the intestines of the host and go outside with bowel movements.

If the egg of the hepatic fluke enters the reservoir, then a larva emerges from it, which is called miracidium. She doesn’t eat, she has cilia with which she moves. Miracidium is looking for a small pond and is introduced into his body.

In the body of a small pond, several larval stages are replaced. In this case, their asexual reproduction occurs. That is, if the pond is infected with one larva of the hepatic fluke, then many new larvae will come out of it.

Larvae of the hepatic trematode, which are called cercaria. They have a tail with which they move. Having reached coastal vegetation, they attach to it, discard their tail, surround themselves with a dense shell, i.e., they turn into cyst. Further, these cysts infect vertebrates.

Thus, a brief life cycle of the hepatic trematode can be described by the scheme:

Worm in a vertebrate animal → Eggs → Free-floating larva (miracidium) → Breeding larvae in a mollusk → Free-floating larva (cercaria) → Cyst → Worm in a vertebrate animal.

But in fact, several generations of larvae are replaced within the mollusk. When miracidium enters the body of a small pond, it turns into sporocyst. She has no cilia, she looks like a shapeless bag. There are germ cells in the sporocyst, from which another generation of hepatic fluke larvae develops - redia. When exiting sporocysts, redia tear it. Then they penetrate into the liver of the mollusk, where they parasitize and reproduce asexually (through parthenogenesis). Several generations of radium can change until cercariae appear, which leave the body of the mollusk through the integument.

The cycle and stages of development of the hepatic trematode

Representatives of the Fasciola species - fasciola hepatica, or hepatic fluke, a class of trematode, are very interesting in the study. The uniqueness of the life cycle, the simultaneous development of hermaphroditic and parthenogenetic generations, the presence of several larval stages that differ from each other in physiological and morphological structure, puts the parasite in a completely separate row.

The systematic position of the hepatic trematode is determined by the Fasciolide family, Latin name Fasciolidae, and represents a type of flatworm. The hepatic trematode belongs to the class of digenetic trematode, which is headed by the order Echinostomatida, consisting of representatives of the genus Fasciola.

The taxonomy classifies the life cycle of development of the hepatic trematode as a complex type that includes several persons involved:

  • main host
  • intermediate host
  • free-living stage of the larval form.

The cochlea is an intermediate host for the hepatic parasite. Parthenogenetic generations of the flatworm develop in the liver of the mollusk, the small Prudovik.

Domestic ungulates and cattle are the main host of hepatic fluke. Flat worm-parasite lives in the ducts of the gallbladder, affecting the liver. In these organs, hermaphrodite develops - a sexually mature individual with the presence of female and male genital organs at the same time.

Liver flu morphology

The appearance of the hepatic trematode resembles a flat sheet. The body length can reach five centimeters, the body width of the parasite is not more than 13 mm. The fluke is very different from other flukes in its body size and the structure of the reproductive system.

Hepatic fluke is a hermaphrodite. Each individual has both female and male reproductive organs - the uterus and testes.

Consider the internal and external structure of the hepatic trematode. The body of the fluke is devoid of cilia. It consists of three layers of muscles that make up the muscular epithelial sac. The front of the parasite is equipped with a clearly visible narrow protrusion. This is the oral sucker used by the parasite to fix in the tissues of the internal organs of the body of its owner. The sharp posterior end of the body is also equipped with a suction cup, due to which the hepatic trematode parasitizes in the bile ducts and liver of the victim, sucking and penetrating deep into the tissues.

Marita of the hepatic trematode - a sexually mature individual, has a relatively developed digestive system. The front of the body is equipped with a mouth that passes into the throat. The muscular pharynx flows into the esophagus. The ramified intestines are blindly closed. Digestion is the only relatively developed function that the hepatic trematode is endowed with. The structure of the excretory system is of the protonephridial type, since it closes the central excretory channel passing along the entire body, and not the anus.

Peripharyngeal ganglion with three pairs of nerve trunks connected by jumpers from the nervous tissue form the primitive nervous system. The fluke is blind, only the free-floating larval stage of the flatworm is endowed with a photosensitive eye, because the development of the hepatic trematode and all stages of the parasite's life pass inside the victim’s body and do not need sense organs.

Physiology of the hepatic parasite worm

Most flukes, including fluke, are hermaphrodites. Reproduction and the sexual process occur in the internal organs of the final host, and the mollusk, the intermediate host, carries larvae that reproduce non-sexually.

The male reproductive system consists of a pair of vas deferens and a copulative organoid. When merging, the testes form the ejaculatory canal. The female genital organs are represented by the ovary, zheltochnik and testicular, leading to the ootype - a specific chamber for fertilizing eggs. It flows into the uterus, ending in a hole through which fertilized invasive eggs are brought out.

In its development, the hepatic fluke is much superior to other types of digenetic flukes.

Hepatica has well-developed functions:

  1. The digestive system - the parasite is fed not only by the oral cavity, but also through the entire surface of the body.
  2. Fixation organs, due to which the worm is firmly strengthened in the bile ducts and liver of the victim.
  3. The reproductive system is also highly functional, producing a myriad of eggs.

The posterior third of the body of the worm, immediately behind the abdominal sucker, contains the uterus with a multi-blade configuration. The location of the unpaired branched ovary is the right side of the upper third of the body. Multiple zheltochniki are located on both sides of an individual. The front of the body contains a highly branched network of testes.

The sexually mature form of the fluke is capable of producing a myriad of eggs, laying them in the bile ducts and the host liver. With the flow of bile, eggs are transferred to the intestines. One who is an intermediate host, produces eggs of the parasite along with feces to the outside. For humans, invasive eggs pose a great risk of infection.

The hepatic trematode causes a difficult to diagnose serious disease, Fascioliasis, which is difficult to treat by therapeutic methods.

Variety of larval stages of the parasite

The stages of development of the larvae and the phase of formation of the hepatic fluke are numerous. The scheme for reaching an adult of sexual reproduction is quite complicated. Let's try to illuminate the development cycles of larvae without complex turns. If you can simplify the material presented, describe the formation scheme in your comments on the article.

In size, the eggs of the hepatic trematode reach a size of 80x135 microns. Each egg is oval and brownish yellow. There is a lid from one pole, from under which under favorable conditions larvae emerge, on the opposite side there is a tubercle.

The egg of the hepatic trematode begins to develop only when it enters the aquatic environment with suitable conditions for the process. Sunlight acts as an activator, and, a month later, larvae, or miracidia of the hepatic trematode, emerge from the eggs.

The body of each miracidia is equipped with:

  • cilia, allowing larvae to move freely in the aquatic environment and confirming the family ties of the hepatic trematode with ciliary worms,
  • a single photosensitive peephole provides positive phototaxis, directing the larva to the light source,
  • nervous ganglion - the primitive nervous system,
  • excretory organs.

ads-pc-1In the tail section are germ cells responsible for parthenogenesis. The front end of the body is equipped with an enzyme-forming gland that allows miracidia to freely penetrate and develop in the intermediate host.

At this stage, the larva does not feed. It gets its development due to the nutrients accumulated in the previous stage. Her lifespan is limited, and is only a day. During this time, miracidium must find a snail and penetrate the body of a small Prudovik.

Having penetrated the mollusk, the larva loses cilia. A sporocyst is formed - the next stage of development of the hepatic trematode. A little more time passes, and sporocysts begin to multiply by parthenogenesis. As a result, the following larval form appears - redia. This generation is parasitic in one host, along with the sportsmen.

The sporocyst has a skin-muscular body in the form of a bag, filled with germ cells. She lacks the circulatory system and the digestive process, eating on the surface of the body. The nervous system and sensory organs are in their infancy. At this stage, the reproduction of the hepatic trematode is carried out by simply dividing the sporocysts - breaking up into parts, they form a myriad of individuals of the daughter generation.

In redia, the larvae of the daughter generation, unlike their previous stage, the formation of life-supporting functions is actively taking place:

  • digestive system, consisting of a digestive tube, pharynx and mouth,
  • pseudo-vagina - an embryonic reproductive system capable of hatching new larval generations.

Some stages of the life cycle of the hepatic trematode occupy a special place. During the period of migration, redia, localized in the liver tissue, in the same way by parthenogenesis, the following type of larva is formed - cercaria.

It should be noted some structural features of cercaria, significantly distinguishing it from previous stages of larvae. The body of cercaria is endowed with a brain, as well as a formed, but not involved digestive system and an eye - an organoid of vision. A well-developed function of fixation in the internal organs of the host, which is characteristic of marita.

The final larval stage of the hepatic trematode occurs in the mollusk liver. The body of the cercaria is endowed with a powerful tail, providing the larva freedom of movement. After the cercaria leaves the body of the pond, it tends to get to the shore from the water, where the last metamorphosis occurs.

Coming to land, the cercaria discards its tail. It goes into a cyst state, attaching itself to coastal plants, falling into the so-called stage of adolescaria. The cyst is able to maintain viability for a long time, until it is swallowed by the herbivore, which is the main host of the hepatic trematode.

This is the invasive stage of the larva, dangerous not only for animals, but also for people whose lifestyle is associated with water bodies.

Thus, in the hepatic trematode, there are two stages in which fasciol is considered infectious:

  1. Miracidium is a threat of infection of the intermediate host.
  2. Stage adolexaria, affecting livestock and people. It causes a disease leading to cirrhosis of the liver, which threatens the patient with a fatal outcome.

The life cycle of the hepatic trematode is designed in such a way that only after passing through each stage of development when the main host enters the body, the fluke becomes sexually mature. Only at this stage is the fertilization process possible, during which the formation of eggs laid by the parasite in the water takes place. From this moment begins a new cycle of development of the hepatic trematode.

Pathogenesis, diagnosis and preventive measures

It is typical for the hepatic trematode to localize and parasitize in the bile ducts and liver, attaching itself to tissues with the help of suction cups. The mouth opening is equipped with spikes that destroy the cells, which cause the degeneration of the organ. The characteristic of fasciola-affected liver is marked as tuberous. When lesions of the choleretic passages develop jaundice of varying severity. The general condition of the patient is individual, and depends on how intensely the organ is affected.

In one case, infection occurs after the patient consumes a poorly fried liver and the so-called transit eggs enter the body. In the other - vegetables not washed after irrigation grown in the coastal zone. Despite the types of lesions, Fascioliasis is considered one of the dangerous infectious diseases.

Preventive measures to prevent epizootic tension in certain regions boil down to disseminating knowledge among the population about the parasite, its biological characteristics, what the larva looks like and what is the appearance of the hepatic trematode. Health education is being carried out to increase personal preventive measures among the population.

Public prevention boils down to the destruction of mollusks along the banks of water bodies. Cattle grazing is of great importance - it is transferred to other pastures.

In conclusion, it should be noted that the life cycle of the hepatic trematode passes exclusively with changes in the intermediate and main host. Localized in the liver tissue and bile ducts of domestic ungulates, the fluke causes a disease that is very difficult. Livestock are rapidly losing their coat and body weight. Without appropriate treatment, exhaustion and death quickly ensue.

A person rarely becomes the target of a hepatic lesion. The larval stages that invade the liver tissue cause Fascioliasis, a dangerous disease for humans with damage to the liver, gall bladder, choleretic ducts, and often the pancreas.

Recommended: Pulmonary fluke - a causative agent of paragonimiasis.

Characterization and Life Cycle

The pulmonary trematode is a reddish-brown parasite of ovoid shape, measuring 1.5 by 1 cm. The thickness reaches up to 3-5 mm. Spines are located on the body, the abdominal and terminal parts are equipped with suction cups. Helminths-hermaphrodites. One individual contains the uterus with ovaries and testes. The eggs are small, golden, with a lid, filled with large yolk cells.

About 10 types of fluke are able to affect a person. Geography of the disease: South Asia, Central Africa and South America.

Helminth has several hosts:

  • freshwater mollusks Melania - the first intermediate host,
  • crabs and crayfish that live in fresh water - an additional intermediate host,
  • mammals (most often from the family of feline, canine, marten), as well as humans - the main host.

  1. In water from parasite eggs, miracidia appear that enter the body of the first intermediate hosts. There pass the first stages of proliferation of fluke: sporocyst, redia, cercaria.
  2. Cercaria falls into the water and invades the body of crayfish or crabs. It goes into the following form of development - metacercaria. It is he who is able to hit the final owner.
  3. The final host, eating arthropods, becomes infected with a fluke. Metacercaria migrates through the digestive tract. Here he is freed from the membranes, penetrates the lungs, less often - other internal organs. Favorite habitat are small bronchi. In the period up to 3 months, young parasites mature and reach puberty.
  4. Sexually mature flukes actively multiply, and the affected final host secretes their eggs with sputum and feces. When eggs enter the water bodies inhabited by the mollusks Melania, a new life cycle begins.

Invasive forms of the parasite infect humans by eating raw or poorly processed crayfish and crab meat. You can also become infected with a fluke when eating mammalian meat (for example, wild boar) containing parasite larvae.

Changes in the body caused by the parasite

The first 2-3 weeks after penetration of the trematode into the body are asymptomatic.

When the larvae move from the gastrointestinal tract to the abdominal cavity, the first manifestations of the disease occur. This period is called abdominal paragonimiasis. It is accompanied by signs of enteritis, hepatitis, sometimes aseptic peritonitis. There are severe abdominal pains, dyspepsia: diarrhea, vomiting.

Vital products of parasites can cause various allergic reactions.

When helminths enter the lungs, pleuropulmonary paragonimiasis begins.

Its acute period is accompanied by symptoms of general intoxication (fever up to 40 degrees, weakness), chest pain, cough with purulent sputum and an admixture of blood, shortness of breath. After a few months, the disease becomes chronic, which can last up to 4 years and is accompanied by periods of exacerbations and remissions.

The basis of changes in organs affected by the parasite is an inflammatory reaction. At the location of the helminth, edema is formed. Blood cells - eosinophils, which, when dying, form pus, accumulate there. Around this focus appears a capsule of connective tissue. Cysts form. They break into the adjacent bronchi. Sputum appears. If the cyst is emptied inside the pleural cavity, a complication arises - pleural empyema.

Later, acute inflammatory processes subside. The foci are sclerosed - replaced by dense connective tissue. With the appearance of a large number of sclerosed foci, the normal functioning of the affected organ is disrupted.

The most difficult is paragonimiasis of the brain.

  • pneumosclerosis
  • empyema of pleura,
  • cardiopulmonary failure,
  • brain abscesses
  • meningoencephalitis.

What is this parasite

The hepatic (Siberian) fluke is a helminth from the class of flukes (trematodes) belonging to the type of flatworms. All flukes are parasitic in the body of vertebrates and invertebrates. Their body shape has bilateral symmetry and resembles a flat leaf or tape flattened in the dorsal-abdominal direction, 1.5 to 3-4 cm long. The surface of the worms is covered with epithelium, under which there is longitudinal and transverse musculature. Inside the body is the parenchyma, which acts as a skeleton that maintains the constant shape of the worm, as well as distribution and excretory functions.

The structure of the hepatic trematode is characterized by the presence of a closed digestive tract, two suction cups on the abdominal side of the body, anaerobic respiration, hermaphroditic reproductive system, and high fecundity.

The insidiousness of the pathogens of opisthorchiasis is as follows:

  1. They are distinguished by a long life span - a parasitic worm can inhabit the human body for 3-4 decades. The first symptoms of the disease often appear in adulthood in people infected in childhood.
  2. They are characterized by extremely high fecundity - up to one million eggs can be laid per day with one mature trematode.
  3. The adult fluke does not live outside the host organism, and the larvae are very resistant to survival in the external environment - they are not destroyed by ordinary detergents, they are not afraid of drying out, water chlorination in water pipes.

Development chart

All stages of development of the hepatic trematode can be briefly represented in the form of successive stages:

  • initial larval phase - mobile forms of miracidia emerge from the eggs, which freely swim and enter the body of the first intermediate host (snails, mollusks),
  • the second larval stage - a different form develops in the body of the snails, it is called a sporocyst and can multiply by parthenogenesis (egg maturation without fertilization),
  • the final larval phase is motile larvae with a tail (cercaria), which leave the body of the intermediate host and attach to the surface of coastal plants,
  • on plants, cercariae lose their tails and become motionless cysts, which in this form can persist for a long time, waiting for the next host,
  • the final stage is the penetration into the body of a person or animal, where the larva settles in the liver and bile ducts, after a month an adult is formed that is able to lay eggs that go outside with feces.

If feces get into sewage and merge into reservoirs where there are freshwater mollusks and fish, then the whole cycle repeats. This scheme allows you to visualize how the formation of hepatic trematode and human infection occurs, which is the beginning of a serious disease, often leading to a sad outcome due to late diagnosis and untimely treatment. Describe yourself once again the path of development of the parasite, and you will understand how well it learned to adapt in the external environment and survive in the human body. However, it can be defeated with the help of modern drugs with the mandatory observance of hygiene rules, which the population needs to be trained from childhood. In addition, prevention plays an important role in preventing the infection of water bodies with sewage and increasing the level of the general sanitary condition of individual regions.

This video talks about the life cycle of the hepatic trematode:

Stages of development of hepatic trematode

The hepatic trematode is a parasite worm that lives in the human or animal body, affecting the liver and bile ducts. Hepatic trematode is widespread throughout the world; it causes a disease called fascioliasis. Most often, the worm parasitizes in the body of cattle and small cattle, although massive and sporadic outbreaks of invasion among people are known. Data on actual incidence vary widely. According to various sources, the total number of infected with fascioliasis ranges from 2.5-17 million people worldwide. In Russia, hepatic trematode is widespread among animals, especially in areas where there are swampy pastures. In humans, the parasite is rare.

The hepatic trematode is a trematode with a flat leaf-shaped body, two suckers are located on its head. It is with the help of these suction cups that the parasite is retained in the body of its permanent host. An adult worm can reach a length of 30 mm. and 12 mm wide. The stages of development of the hepatic trematode are as follows:

Marita stage of hepatic trematode

Marita is the sexually mature stage of the worm, when the parasite has the ability to secrete eggs in the external environment. The worm is a hermaphrodite. Marita’s body resembles a flattened leaf in shape. The sucker mouth is at the front end of the body. Another suction cup is on the abdominal part of the body of the worm. With its help, the parasite is attached to the internal organs of the host. Marita reproduces eggs on her own, as she is a hermaphrodite. These eggs go out with feces. In order for the egg to continue development and go into the larval stage, it needs to get into the water.

Larval stage of the hepatic trematode - miracidia

Miracidium leaves the egg. The larva has an oval oblong shape, its body is covered with cilia. On the front of miracidia are two eyes and excretory organs. The posterior end of the body is diverted under the germ cells, which will subsequently allow the parasite to multiply. With the help of cilia, miracidia is able to actively move in water and look for an intermediate host (freshwater mollusk). After the mollusk is detected, the larva penetrates into its body.

Hepatic fluke larva - Redia

At this time, the body of the parasite lengthens, it has a pharynx, the intestines, excretory and nervous systems are born. In each sporocyst of the hepatic trematode, there can be from 8 to 100 redia, which depends on the specific type of parasite. When the radii mature, they exit the sporocyst and penetrate the mollusk tissue. Within each redium there are germ cells that allow the hepatic trematode to proceed to the next stage.

Stage of circus hepatic trematode

At this time, the liver fluke larva acquires a tail and two suction cups. In cercariae, an excretory system has already been formed and the beginnings of the reproductive system appear. Cercaria leaves the shell of redia, and then the body of the intermediate host, perforating it. To do this, she has a sharp stylet or a bunch of spikes. In this state, the larva can move freely in the water. She attaches to an object and stays on it in anticipation of a permanent owner. Most often, aquatic plants become such objects.

Stage of adolescarius (metacercaria) of the hepatic trematode

This is the final larval stage of the hepatic trematode. In this form, the parasite is ready to penetrate the body of an animal or person. Inside the body of the permanent host, metacercariae turns into marita.

The life cycle of the hepatic trematode is quite complicated, so most of the larvae die, never turning into a mature individual. The life of the parasite can be interrupted at the stage of the egg, if it does not fall into the water or does not find the mollusk of the desired species. However, the worms did not die out and continue to multiply, which is explained by compensatory mechanisms. Firstly, their reproductive system is very well developed. Adult marita can reproduce tens of thousands of eggs. Secondly, each sporocyst contains up to 100 redia, and each redium can reproduce more than 20 cercariae. As a result, up to 200 thousand new hepatic flukes may appear from one parasite.

Animals become infected most often when they eat grass from water meadows, or while drinking water from open standing water bodies. A person will be infected only if he swallows a larva in the adolescari stage. Other stages of the hepatic trematode do not pose a danger to him. In order to prevent the possibility of infection, you should thoroughly wash vegetables and fruits that are consumed raw, and do not drink water that has not undergone the necessary treatment.

Once in the human or animal body, adolescaria penetrates the liver and bile ducts, attaches itself there and begins to reproduce offspring. With their suckers and spines, the parasites destroy the liver tissue, which leads to its increase in size, to the appearance of knolls. This, in turn, contributes to the formation of cirrhosis. If the bile ducts are blocked, then a person develops jaundice.

Hepatic fluke development cycle

Fascioliasis is considered a zoonotic biohelminthiasis, that is, a disease caused by animals. The word "biohelminthiasis" means that for the full development of the hepatic trematode you need to be in the host. Of course, this does not exclude the likelihood of infection when eating poorly washed products (which is typical, for example, for ascaridosis), but you need to keep in mind that staying in the soil is not necessary for the hepatic trematode.

The life cycle of the hepatic trematode is relatively simple and takes place in several stages.

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  1. Fluke eggs enter the environment with feces of livestock, pigs, horses and a sick person, because the worm parasitizes in the liver and biliary system.
  2. The eggs must enter a freshwater body of water (a pond, stream, lake, etc.), where microscopic larvae emerge from them, which penetrate the body of a small pond, a freshwater mollusk belonging to the subclass of snails. In the mollusk's body, larvae develop and divide.
  3. The newly formed larvae (cercariae) leave the body of the pond and settle on aquatic plants. At the same time, they are covered with a dense shell, turning into adolescari. The shell performs a protective function for the larvae - thanks to its presence, they can remain viable for two years.
  4. Infection of animals and humans occurs when freshwater vegetation is consumed, as well as when water is accidentally swallowed while swimming. Once in the intestine, the larvae are released from the membrane and exit through the wall of the intestine into the abdominal cavity.
  5. Due to the complex biochemical mechanisms, the larvae of the hepatic trematode “find” the liver and break through its fibrous capsule, plunging into the thickness of the organ and into the biliary tract.
  6. Not all larvae penetrate into the abdominal cavity: some of them are transferred through the portal vein system. As a result, parasites still get into the liver, because it is the portal vein that flows into it.
  7. Fixed in the liver and bile ducts, the larvae begin to develop in sexually mature individuals. This process takes an average of about 3-4 months, after which the parasites begin to secrete eggs, and the cycle repeats.

In accordance with the accepted biological and epidemiological terminology, humans and domestic animals are the final hosts for the hepatic trematode, that is, organisms in which the parasite larvae turn into mature individuals. In the body of the small pond, reproduction and transformation of larvae occurs, therefore, the mollusk is an intermediate host for the parasite.

Fascioliasis: general characteristic

The incubation period for fascioliasis is up to eight weeks, at which time the active migration of the larvae and their fixation in the liver tissue and in the biliary tract occurs.

The period of clinical manifestations proceeds in the acute and chronic stages.

  • In the acute stage of fascioliasis (which is not observed in all patients), an increase in body temperature occurs, accompanied by bone-joint pain and general malaise. As a result of the action on the body of the vital products of the larvae, a toxic-allergic syndrome develops, manifested by cough, dyspnea attacks, sometimes rashes like hives. Pain in the upper abdomen and in the right hypochondrium, nausea, intolerance to fatty foods are characteristic.
  • The chronic stage of the disease is established when the parasite becomes a sexually mature individual. Patients are concerned about dull pain in the right hypochondrium, complaints of nausea, indigestion, periodic loose stools.

The diagnosis of fascioliasis is established on the basis of serological research methods (RNGA, RIF, ELISA of blood serum), as well as stool microscopy. It should be remembered that the isolation of eggs begins only 3-4 months after infection, therefore, in the acute stage of the disease, fecal examination may be negative.

For the treatment of fascioliasis, praziquantel and triclabendazole are used. In most cases, one course of therapy is enough, after which there is a complete recovery.

DOES IT STILL SEE YOU THAT IT WAS DIFFICULT TO DELIVER FROM PARASITES?

Judging by the fact that you are reading these lines now - victory in the fight against parasites is not on your side.

Surely you have already studied information about antiparasitic drugs? It is understandable, because parasites are dangerous, they actively multiply and live long, causing irreparable harm to your health. Nervousness, impaired sleep and appetite, immune disorders, intestinal dysbiosis and stomach pain. All these symptoms are familiar to you firsthand.

But is it possible to treat the cause rather than the effect? We recommend reading the article by Elena Malysheva on modern methods of getting rid of parasites. Read the article >>

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Watch the video: Liver fluke life cycle explained in detail HINDI (January 2020).