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Experimental respiratory cryptosporidiosis in immunosuppressed rats: a light and electron microscopy study
P Lanzarini1, S Gatti, A Bruno
1Laboratory of Electron Microscopy, University-IRCCS San Matteo, Pavia, Italy.
Abstract:
Cryptosporidium parvum is a coccidian protozoon that causes diarrhoeal enteritis in immunocompetent and immunocompromised humans and other mammals. Sometimes, chiefly in HIV-infected subjects, anatomical sites other than gastro-intestinal tract, such as the biliary and respiratory tree, are involved. We performed an experimental respiratory infection in immunosuppressed albino rats with a C. parvum human-derived isolate, to confirm the possibility of a primary infection at this site and to evaluate the protozoan damages 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 respiratory tract, from the trachea to the median bronchi, without lung parenchyma infection, was observed. Moreover 13/33 (39.4%) rats also developed intestinal infection. TEM study of the respiratory tree specimens demonstrated that cryptosporidia infect either ciliated or goblet cells, and confirmed the role of microvilli in the parasite cell adhesion. The most relevant alterations involved the ciliated cells, with loss of cilia and nuclear and cytoplasmic damages.
Insights
This study shows Cryptosporidium parvum can infect the respiratory tract in immunosuppressed rats, causing damage to ciliated cells. Intestinal infection also occurred in some rats.
Area of Science:
- Parasitology
- Immunology
- Pathology
Background:
- Cryptosporidium parvum causes enteritis in humans and mammals.
- Extraintestinal C. parvum infections occur, particularly in HIV-infected individuals.
- The respiratory tract can be an extraintestinal site for C. parvum.
Purpose of the Study:
- To investigate primary respiratory infection by C. parvum in immunosuppressed rats.
- To evaluate protozoan-induced damage in the respiratory tract using light and transmission electron microscopy (TEM).
Main Methods:
- Immunosuppressed rats were infected intratracheally with a human-derived C. parvum isolate.
- Respiratory and intestinal specimens were collected and analyzed from day 7 post-infection.
- Light microscopy and TEM were used to assess parasite presence and cellular damage.
Main Results:
- C. parvum colonized the trachea and bronchi, but not the lung parenchyma.
- Intestinal infection was observed in 39.4% of the rats.
- TEM revealed C. parvum infecting ciliated and goblet cells, with microvilli involvement in adhesion.
- Significant damage to ciliated cells, including cilia loss and cellular damage, was noted.
Conclusions:
- Cryptosporidium parvum can establish a primary infection in the rat respiratory tract.
- The parasite damages respiratory epithelial cells, particularly ciliated cells.
- The study confirms the potential for respiratory cryptosporidiosis in immunocompromised hosts.