Pulmonary disease in selected protozoal infections.

Protozoa of the phylum Apicomplexa, including the genera Plasmodium, Babesia, Toxoplasmosis, and Cryptosporidium, are a group of closely related organisms that seldom cause pulmonary disease. All but Babesia are members of the subclass Coccidiasina ("Coccidians"). (The fungal organism Coccidioides immitis, a frequent cause of pulmonary disease in endemic areas, was first believed by Rixsford and Gilchrist to be a member of the subclass Coccidiasina; hence its name, meaning coccidioidal-like). Some species, such as Toxoplasma gondii, occasionally cause pulmonary disease by directly infecting lung parenchyma, whereas others, such as Cryptosporidium and Microsporidium, can be occasionally visualized in respiratory secretions or lung biopsy specimens, but their role in causing respiratory disease in human beings is more questionable. In contrast, pulmonary disease associated with infections caused by Malaria and Babesia is often the result of a systemic inflammatory response.