Paragonimiasis Or Pulmonary Fluke: Features Of The Disease

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Paragonimiasis Or Pulmonary Fluke: Features Of The Disease
Paragonimiasis Or Pulmonary Fluke: Features Of The Disease
Video: Paragonimiasis Or Pulmonary Fluke: Features Of The Disease
Video: What is Paragonimiasis ?? ( FAQ and Answers ) 2023, February

Paragonimiasis is a parasitic infection of humans and carnivorous mammals, in which the lungs, subcutaneous fatty tissue, skeletal muscles, and sometimes the brain are affected. Currently, there are more than 30 known species of flukes belonging to the species Paragonimus. However, only 10 of them are parasites in the human body. The most common species is Paragonimus westermani, which is widespread in the Far East.


There are statistics according to which in Korea, China and Japan, infection with pulmonary fluke is about 90% of the total population. Also, the level of infection is quite high in Asian countries and in some countries in West Africa.

This type of helminths parasitizes mainly in the lungs, but they are also able to localize in other organs. The carriers of the infection are not only humans, but also domestic and wild animals. Infection occurs as a result of poor-quality heat treatment of freshwater fish, crabs and crayfish meat.


  1. Description of the disease "Paragonimiasis"
  2. Pathogenesis
  3. Symptoms
  4. Pulmonary paragonimiasis
  5. Extrapulmonary paragonimiasis
  6. Brain damage
  7. Abdominal cavity
  8. Layering of paragonimiasis
  9. Treatment
  10. Forecast and prevention

Description of the disease "Paragonimiasis"

The causative agent of paragonimiasis is the tapeworm Paragonimus westermani (pulmonary fluke, paragonimus) from the Trematode class. The body of the parasite has a length of up to 13 mm by 8 mm, and a thickness of 5 mm. The parasite has a specific ovoid membrane and a red-brown color. The body of this helminth is covered with small thorns, and on its abdomen there is a significant suction cup that covers the middle of the body. The eggs of the parasite are up to 84 microns by 54 microns in size, oval and golden brown in color.

The pulmonary fluke has a very complex developmental cycle. For the maturation of the worm, a change of two intermediate and one final hosts is necessary. The final hosts of the parasite are both domestic cats, dogs, pigs, and wild animals, as well as humans. The route of transmission of the disease caused by parasitism of the pulmonary fluke is fecal-oral.

After the release of the eggs of the parasite together with the feces into the environment, they must enter the freshwater reservoir for the next stage of development. In the water inside the egg, a myracid larva forms, which penetrates into the body of the mollusk, where a number of metamorphoses take place with it. It undergoes successive transformation into sporocysts, redia, and cercariae. Cercariae, after five months of development and asexual reproduction, leave the body of the mollusk, being released into the water, where they penetrate into their next intermediate host, which is the body of a crab or crab. In their bodies, cercariae are encystised in muscles and continue their development, becoming metacercariae, actually invasive larvae. Such a larva needs a final host in order to become sexually mature and begin to reproduce.



This parasitic infection is highly susceptible in humans. Infection with paragonimiasis occurs as a result of eating infected freshwater fish and crayfish, as well as contaminated crab and meat. There is another way of infection - the use of dirty water from stagnant fresh water bodies.

Distinguish between pleuropulmonary and abdominal paragonimiasis.

Pleuropulmonary paragonimiasis develops as a result of parasitism in the host's organism of young helminths.

Abdominal paragonimiasis occurs due to the migration of larvae from the intestine into the abdominal cavity. In this case, symptoms of hepatitis and enteritis, as well as benign aseptic peritonitis, are observed.

The pathogenesis of the disease is manifested by inflammatory processes in the tissues of the lungs and their hardening under the influence of parasitizing these trematodes. The sclerotic process leads to displacement, deformation and a decrease in lung volume. Also, as a result of pulmonary sclerosis, compression of the nerves and blood vessels that feed the tissues of the respiratory system occurs.

Once in the small intestine, the larva sheds its membranes and, piercing the walls of the intestine, begins a difficult stage of migration. Since the larva must get to the lungs, it makes its way through the abdominal cavity, diaphragm and pleura. When it penetrates into the pulmonary parenchyma, it begins to actively create fibrous cysts around itself, which are localized at the roots of the lung. Each such cyst, filled with an inflammatory fluid mixed with blood and mucus, contains several flukes and their eggs.

The location of the cyst in the subpleural region leads to the development of pleural empyema, where there is a large accumulation of eosinophils.

In the lungs, the fluke becomes a sexually mature individual, which begins to actively reproduce. 6 weeks pass from the moment of infection, and eggs are laid after 90 days. The life span of a helminth in the body of the final host lasts 5–8 years.

Pulmonary fluke, its larvae and eggs have a mechanical effect on the lung tissue, which leads to the development of inflammatory and allergic reactions. The passage of the helminth through the peritoneum and diaphragm not only damages the tissues of these organs, but also causes necrosis and hemorrhage in them, which can lead to the development of hypochromic anemia. The rupture of fibrous cysts leads to the spread of pulmonary flukes and their eggs throughout the body: in the central nervous system, lymph nodes, liver, skin and prostate gland.

During damage to the lung tissue, the patient experiences a painful cough with sputum, which contains the eggs of flukes. Since sputum is often swallowed, the helminths enter the digestive system and are excreted with feces. After the rupture, the cyst cavity is healed, and in its place tissue sclerosis and its calcification develops.

Pulmonary flukes, in addition to the lung parenchyma, are able to penetrate into other organs: the abdominal wall, pleura, abdominal organs and the brain. The penetration of a pulmonary fluke into the brain leads to extremely serious consequences. The defeat of the abdominal cavity and liver, as a rule, develops as a result of parasitism of the species Paragonimus skrjabini.


The incubation period of the disease lasts from several days to several weeks. The symptoms of the disease depend on the stage and degree of the disease.

There are two forms of paragonimiasis, depending on the degree of development of the disease:

  • sharp;
  • chronic.

You can also designate the larval form of the disease and the stage of the disease, which is caused by the parasitism of adult worms.

The larval stage is the stage of larval migration throughout the body, which is characterized by the absence of specific symptoms. With massive larval invasion, enteritis, hepatitis, allergy symptoms and itching can occur. And at an early stage of paragonimiasis in the lungs, volatile infiltrates, symptoms of pneumonia and exudative pleurisy are already observed.

Acute pleuropulmonary paragonimiasis is characterized by shortness of breath, acute fever, chest pain, cough with purulent sputum and blood streaks. After a while, these symptoms subside, and a chronic form of the disease sets in with a change in periods of relief and exacerbation, which can last for a long time (within 4 years).

The chronic form is characterized by the development of focal pulmonary fibrosis. On X-ray images, foci of darkening with enlightenment in the center are seen. Probable diffuse pneumosclerosis, pulmonary hemorrhage, lung cancer. The penetration of parasites into the brain is fraught with the development of encephalitis and meningoencephalitis.

There are also two forms of paragonimiasis, depending on the localization of the helminth in the body:

  • pulmonary;
  • abdominal.

The defeat of the lungs with paragonimiasis rarely leads to the death of the patient, however, with the development of the extrapulmonary form, the frequency of complications and deaths is quite high.


Pulmonary paragonimiasis

Pulmonary paragonimiasis also exists in two stages: acute and chronic.

The acute stage of pulmonary paragimosis lasts from several weeks to a year. It is characterized by gastrointestinal symptoms and corresponds to the migration period of this invasion. In other words, the migration period is the period of immature larval forms of the pulmonary fluke.

These early general symptoms last for several days, then symptoms that are characteristic of diseases of the pulmonary system appear:

  • cough with phlegm mixed with blood and mucus;
  • chest pain;
  • dyspnea;
  • general weakness;
  • sweating;
  • fever (low grade or fever).

When trematodes begin to migrate from the abdominal cavity, penetrating through the diaphragm, into the pleural cavity of the lungs, mechanical tissue damage occurs, as a result of which bilateral pleurisy or pneumothorax develops.

Fibrocystic capsules form around the parasites in the lungs, which lead to inflammatory processes and allergic reactions.

In the chronic stage of the disease, both pulmonary symptoms and general symptoms are observed. At this stage, fibrous cysts form around adults. In addition to the worm itself, a brown liquid is formed in the fibrous capsule, in which the eggs float. It is they who come out with phlegm when coughing.

Chronic pulmonary manifestations include:

  • dry cough, with further expectoration of brownish-brownish-yellow phlegm;
  • chest pain;
  • shortness of breath that appears during exertion.

The above symptoms occur six months after infection and are mistaken for symptoms of tuberculosis. However, the absence of temperature and an increase in the number of eosinophils in the blood make it possible to diagnose paragonimiasis.

A complication of the pulmonary form of the disease is:

  • pulmonary bleeding;
  • pneumothorax;
  • abscess of the lung or empyema of the pleura.

A serious complication of pulmonary paragonimiasis is the drift of helminth with blood flow into the brain, followed by the development of cerebral pathology.

Extrapulmonary paragonimiasis

Extrapulmonary forms of the disease develop as a result of the migration of both larvae and eggs, and adults with blood flow to different organs:

  • brain;
  • liver;
  • peritoneum;
  • spleen;
  • mesenteric lymph nodes (located in the abdominal cavity);
  • intestinal wall;
  • spinal cord;
  • subcutaneous tissue;
  • muscles.

Brain damage

Despite the fact that this form of paragonimiasis is extremely rare, it is the most common extrapulmonary form of the disease. With brain damage, urgent hospitalization is required. The early manifestations resemble meningoencephalitis and last for two months. Distinguish between acute and chronic brain damage.

The acute form of the disease is manifested by neurological symptoms, but, as a rule, against the background of pulmonary pathology.

Chronic symptoms:

  • headaches and dizziness;
  • nausea and vomiting;
  • convulsions;
  • paralysis;
  • intracranial hypertension;
  • paraplegia (paralysis of the upper or lower limbs);
  • deterioration of vision;
  • epileptic seizures;
  • hemorrhage.

It should be noted that paragonimiasis of the brain is often fatal.

Abdominal cavity

With the localization of adult parasites or their eggs in the abdominal cavity, granulomas and abscesses form in the walls of the intestines, liver and spleen. The main manifestations are:

  • diarrhea with blood;
  • stomach ache.

When parasites are localized in the kidneys, blood appears in the urine (hematuria) with the presence of helminth eggs. When the spinal cord is damaged, paralysis sometimes develops. With the penetration of paragonimus into the heart, there is a high probability of death.

Layering of paragonimiasis

Diagnosis of the disease is carried out in three directions:

  • collection of anamnesis;
  • laboratory tests;
  • instrumental methods.

The disease is suspected based on clinical presentation. When collecting anamnesis, the doctor conducts a conversation with the patient, during which the patient's taste preferences, the type of professional activity and the existing symptoms are clarified.

Then a number of clinical and instrumental studies are carried out:

  • sputum examination;
  • fecal examination;
  • general blood analysis;
  • Analysis of urine;
  • serological blood tests (ELISA, RSK);
  • tissue biopsy;
  • instrumental examinations (ultrasound, CT, MRI, X-ray)

A general blood test reveals an increased number of eosinophils, leukocytes and ROE. However, an increased level of eosinophils is observed only in the early stages of the disease, followed by a return to normal for a long time. With pulmonary complications, leukocytes either remain within the normal range or slightly increased.


A study of sputum, feces, pleural, cerebrospinal fluid and pus is carried out for the detection of pulmonary fluke eggs. However, these studies are not always informative, since the eggs of the parasite may not be present in sputum and feces for three months.

Biopsies of the lungs, brain, subcutaneous tissue, and abdominal tissues can detect nodules or vesicles. Adult or immature helminths can be found in such samples.

The sputum test should be done several times, since there are not many eggs in one sputum sample. With a simultaneous bronchoscopy and sputum examination, the chance of detecting parasite eggs is very high.

Instrumental studies reveal the disease in 80–90% of cases. The X-ray method can reveal fibrosis, linear and nodular infiltrates, calcified seals in the center, cavitating lesions, fluid accumulation in the pleura, pleural compaction.

Magnetic resonance imaging (MRI) and computed tomography (CT) scan can detect cerebral calcifications, cystic lesions, or hydrocephalus (accumulation of fluid in the brain).

Serological blood tests are highly informative, since paragonimus eggs are extremely difficult to detect in mucus, feces or sputum samples. Such tests are very effective in diagnosing an extrapulmonary form, since in these cases the eggs are not found in feces and sputum.

The most effective is the compliment binding reaction (CSC), but it is advisable to carry out it after treatment, since the level of antibodies decreases 12 months after treatment.

An enzyme-linked immunosorbent assay (ELISA test) of blood is reliable in 90% of cases. The immunoblot test is informative when it is required to distinguish an active infection from a past one. This method is the best in diagnosing the larval form of the disease. It is based on an antigen-antibody immune response.

Allergy skin tests using an extract from an adult paragonimus are very informative, although they can be false-negative. In some cases, skin results may remain positive for up to 20 years after treatment.


The treatment is carried out in several stages. At the first stage, desensitizing therapy is carried out, the essence of which is to eliminate symptoms of an allergic nature. For this, various antihistamines and corticosteroids are used.

The next step is anthelmintic therapy, which consists in eliminating the immediate cause of the disease. These are the latest generation of antihelminthic drugs:

  • praziquantel in a daily dose of 60-75 mg per 1 kg of body weight, which is divided into three doses after meals, with an interval of 4 hours, the course of treatment is 2 days.
  • bitinol (tetrachlorodiphenyl sulfide) at a dose of 30-50 mg per 1 kilogram of body weight, every other day three times a day;
  • triclabendazole is used at a dose of 10 mg per 1 kilogram of body weight / kg per day for 3 days.

In case of brain damage, treatment is carried out in a hospital under the supervision of a doctor. In this case, the following treatment is prescribed:

  • detoxification measures;
  • diuretics;
  • anticonvulsants;
  • nootropic and neuroprotective drugs;
  • medicines that improve blood circulation.

In the treatment of the chronic stage, the following are prescribed:

  • immunostimulating drugs;
  • vitamin and mineral complexes;
  • drugs that have a beneficial effect on the work of the cardiovascular system;
  • restorative physiotherapy procedures.

In extremely severe cases, surgical intervention is possible, which involves:

  • lung resection;
  • exfoliation of cysts from the lungs;
  • removal of calcifications from the brain.

Forecast and prevention

With timely and adequate treatment, the outcome is favorable. In advanced cases, serious complications can develop: pulmonary insufficiency, encephalitis, general exhaustion, and others. If the brain or heart is damaged by a pulmonary fluke, the prognosis is poor.

Prevention of paragonimiasis is reduced to the following activities:

  • to carry out high-quality heat treatment of meat of crabs, crayfish and fish of the carp family;
  • use only purified or boiled water;
  • to protect fresh water bodies from infestation by flukes;
  • decontaminate feces before using them as fertilizer;
  • do not allow feces to enter groundwater and water bodies;
  • personal hygiene.

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