Overview.
Many parasites that are transmitted throughout the body via the bloodstream often reside in the lungs and cause lesions known as pulmonary parasitosis. This includes parasites whose larvae need to pass through the lungs during development and parasitic infections in which the adult worms use the lungs as a host site. Pathogenic parasites of the lungs include protozoa, helminths, arthropods, trematodes and mites.
Lung parasitism is either caused by direct invasion of the lungs (pleura) or by an allergic reaction. The former can be a primary lung infection such as Pneumocystis carinii pneumonia or secondary to the spread of neighboring organ lesions such as pleuropulmonary amebiasis; the latter manifests itself as various types (simple, migratory, tropical) of pulmonary eosinophilic infiltrates, mostly accompanied by helminthic migratory disease.
Etiology
1. Parasitic diseases in which the lungs are the main host site. For example, Pneumocystis carinii.
2. Parasitic diseases that take other parts of the body as the main parasitic site can sometimes invade the lungs, such as amoebic lung abscess, pulmonary cysticercosis, and so on. Porcine cysticercus can occasionally parasitize lung tissue, but it is less common and the symptoms are not obvious.
3. The larvae of some parasites need to stay and develop in the lungs during their development, which can also cause lung lesions, such as filarial worms, especially some parasitic filarial worms in the body of other animals, whose larvae can not develop in the human body, but can cause tropical eosinophilia. The larvae of Ascaris lumbricoides, especially the larvae of Ascaris lumbricoides pigmentosus, can also cause lung lesions in humans.
4. In addition, parasites from other parts of the body, such as liver fluke, can cause allergic reactions in the lungs, manifesting as hypersensitivity pneumonitis.
Symptoms
Parasitic diseases of the lungs have common clinical features.
1. Respiratory symptoms
Patients often have cough, mostly dry cough, but also with sputum, usually a small amount of white mucous sputum, occasionally with blood. Amebic lung abscess patients cluck chocolate-colored sputum, the amount is also more, sputum can sometimes be found in lysed tissue within the amoebic trophozoites. In patients with schistosomiasis, the sputum is jam-like or meat-like, and eggs of Schistosoma japonicum and crystals of Salko-Redden’s diatoms can be found in the sputum. In the case of acute epidemic asthma caused by Ascaris lumbricoides larvae, patients often have fever, cough, shortness of breath and asthma attacks.
2. Chest pain or pleural effusion
When the foci of pulmonary parasitic diseases are adjacent to the pleura, it can often cause chest pain, and sometimes pleural effusion can be seen, and the eosinophils in the pleural fluid are obviously increased.
3. Increased eosinophil count in peripheral blood.
Most of the patients with pulmonary parasitic disease have mild increase in peripheral blood eosinophil count, but it is obviously increased in fulminant epidemic asthma, tropical eosinophilia, Sichuan schistosomiasis, and so on.
Examination
Intradermal tests are important in the diagnosis of patients with pulmonary parasitosis and are valuable in ruling out or suspecting certain parasitic diseases.
1. Serum immunologic test
Indirect hemagglutination test, complement binding test, indirect immunofluorescence antibody technique or enzyme-linked immunosorbent assay are commonly used to help confirm the diagnosis of pulmonary parasitosis.
2. Chest X-ray
It is important for the diagnosis of lung parasitosis. If there are cystic shadows in the lungs on chest X-ray, combined with the patient’s history of living in pastoral areas, positive intradermal worm test and serum enzyme-linked immunosorbent assay, then the diagnosis can be made as pulmonary parasitosis.
3. Sputum examination
Finding eggs, larvae or protozoan trophozoites (such as amoeba and Pneumocystis carinii) in the sputum of the patient is of great significance in making pathogenic diagnosis. Sometimes, a large number of eosinophils or Schalko-Redden’s diathesis crystals are found in the sputum, which is of some reference value for the diagnosis of pulmonary parasitosis.
4. Lung biopsy
In a few cases, especially in patients with pulmonary sporotrichosis, if the diagnosis is still not confirmed after the above examinations, lung biopsy can be used, but this is an injurious examination method, which must be carried out with great caution.
Diagnosis
Diagnosis can be made on the basis of the cause of the disease, clinical manifestations and laboratory tests.
Treatment
In the acute stage, if there is fever, bed rest, nutrition and supportive therapy should be provided. Severe cases can be treated with adrenocorticotropic hormone. In the chronic stage, the treatment of the primary disease is the main focus, and those with anemia and malnutrition should be treated with supportive therapy. Advanced patients should be given low-salt, high-protein diet, increase nutrition and improve the general condition. For those with obvious reduction of plasma protein with high abdominal effusion, plasma or human albumin can be transfused, and appropriate diuresis can be used. Splenectomy with retroperitoneal fixation of the greater omentum is used for the giant spleen type.