Experimental respiratory cryptosporidiosis in immunosuppressed rats: A light and electron microscopy study

Cryptosporidium. parvum is a coccidian protozoon that causes diarrhoeal ent eritis in immunocompetent and immunocompromised humans and other mammals. S ometimes, chiefly in HIV-infected subjects, anatomical sites other than gas tro-intestinal tract, such as the biliary and respiratory tree, are involve d. We performed an experimental respiratory infection in immunosuppressed a lbino rats with a C. parvum human-derived isolate, to confirm the possibili ty of a primary infection at this site and to evaluate the protozban damage s by light and also by transmission electron microscopy (TEM). The animals were infected intratracheally with 1 x 10(6) C, parvum oocysts/ml and, from the 7th day post-infection, biological specimens of trachea, bronchi, lung and ileum were zoopsied. A sole cryptosporidial colonization of the respir atory tract, from the trachea to the median bronchi, without lung parenchym a infection, was observed. Moreover 13/33 (39.4 %) rats also developed inte stinal infection. TEM study of the respiratory tree specimens demonstrated that cryptosporidia infect either ciliated or goblet cells, and confirmed t he role of microvilli in the parasite cell adhesion. The most relevant alte rations involved the ciliated cells, with loss of cilia and nuclear and cyt oplasmic damages.