Special Features journal.publications.chestnet.org CHEST / 145 / 4 / APRIL 2014 883 CHEST H elminthic and protozoal infestations cause signif- icant morbidity and mortality worldwide. A decline in parasitic infestations has been observed in the past decade as a result of improved socioeconomic condi- tions and better hygiene practices. However, the rapid urbanization of cities around the world, global warm- ing, international traveling, and increasing numbers of immunocompromised individuals have increased the vulnerability of the world population to parasitic diseases. 1 The diagnosis of parasitic diseases of the respiratory system is challenging because the clinical manifestations and radiologic findings are nonspecific. Thus, a high index of suspicion and detailed interro- gation regarding travel history are critical. Most para- sitic infestations of the respiratory system either involve the airways or require bronchoscopy for diagnosis. Hel- minthes can affect the airways during both the larval and the mature adult phases of their life cycle. The larvae can cause airway inflammation (paragonimiasis), whereas migration of the mature adult worms may cause mechanical obstruction of the airways (ascariasis). This article provides a comprehensive review of both helminthic and protozoal infestations, including clin- ical, radiographic, bronchoscopic, and pathologic man- ifestations, that may be helpful to pulmonologists in managing this important entity (Table 1). Nematodes Nematodes, also known as roundworms, have a sym- metrical, tube-like body with an anterior mouth and a longitudinal digestive tract. Ascariasis Ascaris lumbricoides is one of the most common parasitic infestations, affecting . 1 billion of the world’s population and causing . 1,000 deaths annually. 1 A lumbricoides is transmitted via the feco-oral route. An Ascaris larva migrates to the lungs through either the lymphatics or the venules of the portal system. Larval ascariasis causes Löffler’s syndrome, a concomitance of wheezing, pulmonary infiltrations, and eosinophilia. 2 It can cause alveolar inflammation, necrosis, and hem- orrhage. Diagnosis of an ascariasis infestation during its larval phase is difficult. The sputum may show numer- ous eosinophils; stool examination, however, remains negative for eggs during the larval stage. 3 The diagno- sis requires a high degree of suspicion. Occasionally, Parasitic infestations affect millions of the world’s population. Global immigration and climate change have led to changes in the natural distribution of parasitic diseases far removed from endemic areas. A broad spectrum of helminthic and protozoal parasitic diseases frequently affects the respiratory system. The wide varieties of clinical and radiographic presentations of parasitic diseases make the diagnosis of this entity challenging. Pulmonologists need to become familiar with the epidemiology, clinical presentation, pathophysiologic characteristics, and bronchoscopic findings to provide proper management in a timely fashion. This review provides a comprehen- sive view of both helminthic and protozoal parasitic diseases that affect the respiratory system, especially the airways. CHEST 2014; 145(4):883–895 Abbreviations: BALF 5 BAL fluid; DEC 5 diethylcarbamazine; ELISA 5 enzyme-linked immunosorbent assay; PAH 5 pulmonary artery hypertension; TPE 5 tropical pulmonary eosinophilia Parasites of the Air Passages Danai Khemasuwan, MD, MBA; Carol F. Farver, MD; and Atul C. Mehta, MD, FCCP Manuscript received September 1, 2013; revision accepted December 16, 2013. Affiliations: From Pulmonary, Allergy and Critical Care Medicine (Drs Khemasuwan and Mehta), Respiratory Institute, and the Department of Anatomical Pathology (Dr Farver), Cleveland Clinic Foundation, Cleveland OH. Correspondence to: Atul C. Mehta, MD, FCCP, Pulmonary, Allergy and Critical Care Medicine, Respiratory Institute, Cleveland Clinic Foundation, 9500 Euclid Ave, A-90, Cleveland, OH 44195; e-mail: Mehtaa1@ccf.org © 2014 American College of Chest Physicians. Reproduction of this article is prohibited without written permission from the American College of Chest Physicians. See online for more details. DOI: 10.1378/chest.13-2072 Downloaded From: http://journal.publications.chestnet.org/ by Cleveland Clinic, Atul Mehta on 04/01/2014