Diagnosis of Pulmonary Parasitic Diseases

The protozoal and helminthic parasites that traverse the respiratory tract during their life cycles can cause lung diseases, though the most common habitats of these parasites are the gastrointestinal tract and the blood or lymphatic circulations. These diseases are commonly encountered in the tropical regions of the world. However, parasitic lung diseases are increasingly being reported from other parts of the world due to an increase in the occurrence of immunosuppression (acquired immunodeficiency syndrome, organ transplantations, the use of immunosuppressive drugs) and transcontinental travel. The lung diseases that may result from these infections range from asymptomatic phase to life-threatening acute respiratory distress syndrome. These diseases can also mimic common respiratory diseases such as bacterial pneumonias, pulmonary tuberculosis, lung cancer, bronchial asthma, interstitial lung disease, and pulmonary hypertension. The diagnosis of parasitic lung diseases is a challenge to physicians, if they are not aware of the entity or these diseases are not investigated properly. The diagnosis of these diseases is based on the identification of the causative organism in the stool, sputum, other body fluids, or tissue specimens. Radiological imaging studies of the thorax including chest radiographs, high-resolution computerized tomograms, and ultrasonograms may aid in the diagnosis. In certain situations, invasive investigations such as fiberoptic bronchoscopic evaluation (transbronchial lung biopsies and bronchoalveolar lavage studies) and thoracic surgical procedures (thoracoscopy and open lung biopsy) may be required for a diagnosis and also to exclude other lung diseases. Serologic and molecular diagnostic methods are being developed for accurate diagnosis of the parasitic diseases.