Parasitic infections of the human lung are rare. They are commonly seen in other species. Nevertheless, in some parts of the world they are endemic (schistomiasis). This presentation will discuss some relatively common parasitic diseases that may involve the lung.
Protozoa
Amebiasis: Infection by the protozoan Entamoeba histolytica.
Found worldwide but most common in tropical areas.
High rate of infection in Mexican Americans.
Among homosexual men: sexually transmitted disease.
Clinical aspects: Pleuropulmonary complications of amebic abscess (7 to 20% of patients).
Occurs: Direct spread from diaphragm
Hepatic abscess rupture
Hematogenous spread
Pathology: Multiple abscesses. Trophozoites (15-25µm)
PAS stain
Cryptosporidiosis: Infection with cryptosporidium parvum.
Intestinal protozoan that rarely affects the lung
Clinical aspects: cough, dyspnea, fever
Commonly seen in immunosuppressed patients
10-15% of patients with AIDS develop pulmonary microsporidiosis
Associated processes: CMV, Pneumocystis carinii, Mycoplasma pneumoniae, Legionella or Aspergillus pneumonia
Diagnosis: acid fast oocysts in sputum or BAL
Pathology: Tracheobronchitis and bronchiolitis
Organisms: 4-6µm in diameter
Microsporidiosis: Infection caused by Encephalitozoon sp and Enterocytozoon bieneusi.
Obligate intracellular organisms.
Pathology: tracheobronchitis
Gram-positive organisms, weakly acid fast.
Nematoda
Dirofilariasis: Infection caused by Dirofilaria immitis (the dog heartworm)
Transmitted from dogs to humans by mosquitoes of the genera Aedes, Culex, Myzorhynchus, and Anopheles
Pathology: well circumscribed nodules. Eosinophilia
Strongyloidiasis: Involves: skin, lung, intestine
Pathology: hemorrhage, cavities and abscesses. Massive pulmonary hemorrhage or diffuse alveolar damage.
Trematoda
Paragonimiasis: Infection caused by Paragonimus sp. (oriental fluke)
48 species and subspecies have been described. Most commonly found in Asia.
Pathology: worms seen adjacent to bronchioles, surrounded by abscess and fibrous wall forming cysts. Organisms measure 1-3 mm in diameter. Secondary bronchopneumonia.
Schistosomiasis: Infection caused by Schistosoma mansoni, S. japonicum or S hematobium. (Mansoni: Africa, Brazil, Puerto Rico. Japonicum: Philippines, China, Japan. Hematobium: Africa, southern Europe, western Asia)
Pathology: Granulomatous inflammation, fibrosis, pulmonary hypertensive lesions.
Cestoda
Echinococcosis: Infection caused by tha larval tapeworms: Echinococcus granulosus, multilocularis and vogeli .
Most common site of E. granulossus: liver followed by lung.
Pathology: Hydatid cyst. Rupture may lead to anaphylactic shock
Artifactual structures that may resemble parasitic infections.
Calcifications, mineralization, histological artifacts.
