Trematodes: Definition, Life Cycle, Causes, Symptoms, Diagnosis and Treatment

About forty species of flukes are dangerous to humans due to their infectivity.

Trematodosis is a group of diseases caused by tapeworms of one of four available classes, the class of flukes (flukes).

Life cycle

The trematode is very complex; it can happen by replacing an intermediate host. Almost all flukes are hermaphrodites, except schistosomes.

The existence of a class of flukes is associated with the fertility of a large number of offspring. The larvae of each stage can carry out the reproduction process not only by parthenogenesis but also by a cross-over method.

Causes of flukes

The class of flukes includes five species of sciatica:

  • Flaky
  • Pulmonary.
  • Felina.
  • Hepatic.
  • China.

Furthermore, schistosomes, also representatives of trematodes, can cause human trematodes.

Like most parasitic worms, trematodes have attachment organs that keep them on the wall of the affected organ; This is the abdominal and oral sucker that it takes to the mouth.


The anal opening is absent; the discharge is carried out through the excretory pore that occupies the position at the rear end of the body. The body of the flukes is a muscular sac of the skin that is leaf-shaped.

All stages of trematode development are capable of reproducing by parthenogenesis. They are hermaphrodites and also to cross the brood.

During the development of the larval specimen matures with the replacement of several intermediate hosts, most of the individuals of the larval stage die.

Therefore, nature has endowed them with a powerful ability to reproduce to maintain the optimal number of individuals in the trematode population.

The flukes deposit many eggs, which are found in the feces of the final host, and are released into the environment.

For the development cycle to continue, the eggs must fall under favorable conditions, that is, in the warm waters of the coastal zone, where the first larval form, the miracidium, emerges.

Miracidium can move in a warehouse. Its body is covered with a multitude of cilia.

In addition, miracidia are swallowed by the gastropod mollusk – this is the first intermediate host for trematodes.

For each type of trematode, a specific type of mollusk is needed as an intermediate host.

The parasites of cats and pigs are mollusks of the genus Bitinia; for the pulmonary parasite, there are mollusks of the genus Melania and Semisulkospir, for mollusks of the genus Planorbis, Fizopsis, Onkomelania, and others (for each species the schistosomes are different).

In the mollusk body, the miracidia reproduce and pass into the larval stage – sporocysts. They, in turn, mature and, by multiplying, give rise to the next larval stage of the larvae-rhodium (daughter sporocysts).

From the sporocysts, cercariae develop, emerging from the body of the freshwater mollusk.

In addition, cercariae can transform into a cyst form (adolescaria, an infectious form of the liver fluke) attached to the leaves of aquatic vegetation.

This, in turn, can be swallowed by a second intermediate host and pass to the metacercaria stage; then, the infection occurs through poorly processed meat, which is characteristic of lung and Chinese flukes.

When the final host (a vertebrate) enters the body from an invasive form (the proper one for each type of trematode), a mature individual emerges marita.

How does trematode infection occur?

Human fluke infection can occur from eating unwashed vegetables when improperly processed or unsalted thermally processed fish meat is eaten.

Symptoms and signs

For all flukes, two general syndromes can be distinguished:

  • Poisoning.
  • Allergic manifestations syndrome.

The intoxication syndrome is associated with allocating flukes to the host organism of poisonous products of their vital activity.

The symptoms of this syndrome are quite general and are not always noticed by a sick person.

These symptoms can include:

  • Headache.
  • Soft spot.
  • Decreased appetite.
  • Sickness.
  • Drowsiness.
  • Rapid onset of fatigue.

All are manifestations of intoxication.

The allergic syndrome is associated with sensitization of the products of the human body from the exchange of helminths and the effects of the destruction of the worm’s body after its death.

Clinically, the allergic organism manifests itself in the form of recurrent skin eruptions that are not very treatable.

In addition to rashes, allergization of the body leads to the appearance of vasculitis and eosinophilic infiltration of internal organs, which disrupts their normal functioning.

Human trematodosis manifests as damage to the liver, gallbladder, and their ducts, and obstruction of the respiratory tract, sometimes the pancreas.

The union of flukes with suction cups and hooks causes damage to the walls of the pancreatic and bile ducts with the development of hemorrhagic erosions and the accumulation of depleted epithelium and parasitic flukes in the ducts of the pancreas, and the gallbladder complicates the discharge of secretions from these organs.

This causes the development of pancreatitis, cholangitis, cholecystitis, and the expansion of the outflow ducts. This is manifested by acute pain in the right or left upper quadrant, possibly the appearance of ring pains.

The defeat of the flukes of the pancreas can provoke the manifestation of diabetes mellitus.

When fluke parasites in the liver, they can remain normal in size. More common is a moderate increase in the liver. Long-term irritation of liver tissue can lead to the development of malignant tumors.

In the case of trematodosis caused by lung flukes, the diaphragm, pleura, small bronchi, and lung tissue are affected.

In the affected organs, hemorrhages and inflammatory changes occur. Bronchitis, focal pneumonia, and pleurisy develop.

At this stage, helminth eggs are found in sputum, and the following symptoms:

  • Fever.
  • Cough with purulent sputum.
  • Difficulty breathing.
  • Chest pain.
  • Bleeding from the lungs

The process is completed with the formation of a fibrous capsule and its calcification.

Penetration of flukes into the brain is accompanied by abscesses, an inflammation of the brain’s substance, and the brain’s membranes developing.

The parasitization of flukes in the brain can provoke the appearance of epileptic seizures.

Diagnostic methods for flukes

The diagnosis of flukes begins with an anamnesis. Hygienic habits of the patient and food preferences or, more precisely, if the patient consumes freshwater fish and how it is prepared before serving at the table.

A general blood test can reflect the course of inflammatory processes in the body (accelerated SWR, leukocytosis), as well as the presence of sensitization in the body (eosinophilia).

In most cases, stool analysis for helminth eggs is crucial.

The biochemical blood test will show an increase in liver enzymes, dysproteinemia, alkaline phosphatase increases, and changes in the indices of catholic and school samples.

For the flukes caused by the schistosome, the definition of eggs is essential not only in the feces but also in the urine.

The type of eggs found in the feces determines the kind of helminths, and the corresponding diagnosis is made.

Fluke eggs can also be found in stool analysis. Egg detection is more likely than accidental.

Helminths can also be detected during duodenal probing. The three secretions received are subject to study. Duodenal probe results are not always reliable.

In patients with flukes, dyskinesia of the bile ducts is often seen, making it difficult for bile to escape. Before conducting a blind probing, patients require special training.

If the patient has a prolonged, untreatable cough, an X-ray examination of the chest is performed. In X-ray photographs, an increase in lung patterns can be seen in flying infiltrates.

In the sputum of such a patient, you can find helminth eggs. This becomes possible in the chronic stage of trematodes when the trematodes reach puberty.

An essential role in diagnosing flukes in humans is an ultrasound examination of the abdominal cavity. It is possible to detect adult parasites in the liver (chronic stage of trematodosis).

In the acute stage, parenchymal changes in the liver and pancreas, enlargement of the liver, gallbladder, and pancreas, expansion of their ducts, and inflammatory changes in these organs are determined.

ELISA, RNA serological reactions can be used in the acute trematode stage. However, they often give false-positive results.


Treatment of flukes in humans consists of eliminating the parasite from the body.

The training takes place in outpatient settings; its purpose is to achieve the normal functioning of the affected organs.

In the presence of dyskinesia of the bile ducts, therapy is performed that normalizes the outflow of bile from the gallbladder. Appropriate medications are prescribed depending on the type of dyskinesia (for hypertonic or hypotonic type).

To improve colic flow, we carry out Demyanov tests twice a week. It is recommended to drink warm mineral water 45 minutes before meals. The duration of use is one month.

In severe allergic manifestations, antihistamines (Suprastin, Loratadine, Catrin, etc.) and membrane stabilizers (lipoic acid, vitamin E) are prescribed in doses depending on age.

In the presence of inflammatory changes in the liver parenchyma, the treatment of flukes in humans requires the connection of hepatoprotective drugs (Essentiale-N, Korsil, etc.).

After training, the course of taking anthelmintic preparations is carried out. Treatment is done in the hospital to monitor the function of the major organs and systems.

Anthelmintic drugs like Praziquantel have excellent activity. The daily dose is sixty milligrams per kilogram of the patient’s body weight. The admission course is one day.

For children, the daily dose of the drug is divided into three equal amounts that the child receives twenty to thirty minutes after eating. The interval between taking certain parts of the drug should be four hours, but no more than six hours.

After taking anthelmintic drugs, the first stage is repeated for 12-14 days.

Human flukes caused by schistosomes can be treated with Metrolonate. It is an alternative drug with intolerance to Prazikvantel.