Paragonimosis: Causes, Symptoms, Diagnosis, Treatment

Paragonimosis is a biogelmintosis, manifested mainly by the defeat of the respiratory system. Paragonimosis is characterized by a prolonged recurrent course.

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Epidemiology of paragonimosis

The source of the invasion is pigs, dogs, cats, wild carnivores and people invaded by paragonimus. Transmission ways - food, water. Transmission factors are the thermally unprocessed meat of crabs and crayfish.

At the optimum temperature (27 ° C) eggs develop in water after 3 weeks. However miracidia can come out of them and after a few months, which is facilitated by the fluctuation of water temperature. Intermediate hosts are freshwater gastropods Melania libertina, M. Externa, M. Amurensis (Far East), Ampullara luteosota (South America) and others, which consistently develop the stages of sporocysts, redias and cercariae. Cercariae actively penetrate into additional hosts through sites with a thin chitinous cover - freshwater crabs of the genera Potamon, Eriocheir, Parathelphusa, cancers of the genera Cambaroides, Procambarus and others.

In crustacean cercariae, they are encysted in muscles and internal organs, where they are transformed into metacercariae, which become invasive after 1.5 months. In the body of a crustacean, several hundred metacercariae can be contained. The final hosts are pigs, dogs, cats, wild carnivores, rodents (rats, muskrats) and people who become infected when eating crabs and crayfish in raw or semi-moist form. Infection can also occur through water, since the death of infected crustaceans metacercariae retains viability in water up to 25 days. In the duodenum of the final hosts, the larvae are released from the membranes, penetrate through the intestinal wall into the abdominal cavity, dig the diaphragm, both the pleura leaf and penetrate into the lungs. Here, around the parasite, fibrous cysts of the size of a hazelnut are formed, localized near the roots of the lungs and along the periphery of the lung tissue. In a cyst, a person usually has one parasite, less often two. Parasites reach sexual maturity and begin to lay eggs after 5-6 weeks after infection. The lifespan of parasites in the lungs is more than 5 years.

Paraguonimosis is prevalent mainly in the countries of Southeast Asia (China, Taiwan, the Indochina Peninsula, Indonesia, the Philippines), as well as in South America (Peru, Ecuador, Colombia, Venezuela). In Russia, in addition to imported cases, there are known foci of paragonimosis in Primorsky Krai and in the Amur region. In this region, the infection is facilitated by eating a local dish - "drunken crabs", which is prepared from live crabs or crayfish, sprinkled with salt and drenched in red wine.

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What causes paragonyema?

Paragonimosis is caused by the pulmonary flukes Paragonimus westermanii and some other species of the Paragonimidae family .

P. Westermanii - thick, broadly oval trematode, reddish-brown in color, reminiscent of coffee beans. Dimensions of the pulmonary fluky body are 7.5-12 x 4-6 mm at a thickness of 3.5-5 mm. Cuticle covered with spinules; oral and abdominal suckers of almost the same size. The intestinal branches are convoluted and extend to the end of the body. Two lobular testes are in the posterior third of the body. Lobular ovary and loops of the small uterus are located near the front of the testes. The sex holes are at the posterior edge of the abdominal sucker. Strongly developed vitellaria are distributed throughout the body from the level of the pharynx to the posterior end of the body of the fluke.

Eggs are oval, golden brown in size, 61-81 x 48-54 microns, with a thick shell, lid and a small thickening at the opposite end. Eggs are allocated immature.

Pathogenesis of paragonymosis

In the pathogenesis of paragonimosis, the leading role is played by toxic-allergic reactions and the mechanical action of helminths and their eggs on the tissues. During the migration of parasite larvae into the lungs through the diaphragm and other organs (liver, pancreas, kidneys), hemorrhages, and sometimes necrosis, are noted in them. In the lungs (especially in the lower lobes), in addition to hemorrhages, eosinophilic infiltrates and exudate accumulations are formed. Later, parasites form fibrous cysts measuring 0.1 to 10 cm in size. They are filled with a mass of gray-white, chocolate or dark red color, contain mucus, eosinophils and other leukocytes, Charcot-Leiden crystals, and one or more parasites. Cysts often communicate with the branching of the bronchi. After the death of the parasite or its release from the cyst, its cavity is cicatrized. When the wall of the cyst is broken, parasites or their eggs are sometimes recorded in the brain, mesenteric lymph nodes, prostate, liver, skin and other organs and tissues.

Symptoms of paragonymosis

The incubation period of paragonimosis lasts 2-3 weeks, with massive invasion can be reduced to several days.

In the acute period of the disease, the first symptoms of paragonimosis develop due to severe enteritis, hepatitis and benign aseptic peritonitis, accompanied by signs of an "acute abdomen". Then there is a fever, chest pains, shortness of breath, cough with purulent sputum, sometimes having an admixture of blood. During physical and radiological studies, exudative infiltrates, and sometimes signs of exudative pleurisy, are revealed.

After 2-3 months, the disease passes into a chronic stage, characterized by periods of remission and exacerbations, during which typical paragonimosis symptoms occur : the temperature rises to 38-40 ° C, chest pains, headaches, dyspnea, coughing with rusty sputum , which contains eggs of helminth. Often there is hemoptysis. When radiographic examination of the lungs are defined weakly rounded shadows with a diameter of 5 to 40 mm with radial linear dimming off from them. As the fibrous cysts form within the shadows, bright vacuoles with clear and smooth contours of 2-4 mm are visible.

After 2-4 years, the clinical symptoms of paragonimosis gradually disappear. After the disappearance of the symptoms of the disease during X-ray examination in the lungs, small isolated foci of fibrosis and single or multiple foci of calcification with a diameter of 2-5 mm are found.

With intensive invasion and long-term course of the disease, pneumosclerosis and "pulmonary heart" syndrome can develop.

The contact of paragonimus in the central nervous system causes the development of symptoms of meningitis, the intracranial pressure rises. Possible development of atrophy of the optic nerve, paresis, paralysis, sensitivity disorders, epilepsy. On radiographs of the brain in such patients, calcified rounded formations containing dead helminths are revealed.

Complications of paragonymosis

Timely treatment of paragonimosis of uncomplicated cases gives a favorable prognosis of the disease. In the case of brain paragonism with multiple cysts, the prognosis is extremely unfavorable.

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Diagnosis of paragonymosis

Differential diagnosis of paragonimosis is carried out with pneumonia, tuberculosis and lung echinococcosis, as well as tumors. With paragonism of the brain, the disease is differentiated with a brain tumor and meningoencephalitis. The parasitic nature of the disease is indicated by a combination of neurological symptoms with characteristic changes in the lungs and the presence of eggs in sputum.

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Laboratory diagnostics of paragonymosis

The diagnosis of "paragonimosis" is established on the basis of epidemiology, clinical data and the results of radiation research methods (radiography, CT, MRI), as well as the detection of parasite eggs in sputum or feces, where they fall when swallowing sputum. In the early period, when the eggs are not yet released by young parasites, ELISA can be used for diagnosis. You can also use an intradermal allergic test with paragonimus antigens.

Treatment of paragonymosis

Specific treatment of paragonimosis should be carried out after relief of allergic manifestations. The drug of choice is prazikvantel (azinoks), which is prescribed to adults in a daily dose of 75 mg / kg in 3 divided doses for one or two days. When CNS is affected, specific therapy should be performed only in a hospital in connection with the possible development of cerebral edema and increased intracranial pressure. Patients are prescribed diuretics and anticonvulsants. Single cysts are removed surgically.

Triklabendazole, also prescribed in the same dosages as in fascioliasis, is also effective.

In order to control the effectiveness of specific treatment of paragonimosis 2-3 months after the end of therapy, a three-time (with an interval of 7 days) control examination of sputum is carried out.

How to prevent paragonism?

In the foci of paragonimosis, crustaceans can only be eaten after cooking, which ensures the death of paragonimus. Due to the fact that the water can contain particles of dead crabs and crayfish invaded by metacercaria, when swimming in open freshwater reservoirs, one should beware of accidental ingestion of water. Paragonimosis can be prevented if only boiled or filtered water is used for drinking. It is necessary to ensure the protection of reservoirs from fecal contamination.