Biomedical Engineering Reference
In-Depth Information
class of Class Animalia. Class Choanozoa contains one genus, with one
species that is pathogenic in humans: Rhinosporidium seeberi.
Choanozoa
Ichthyosporea (same as Mesomycetozoea)
Dermocystida
*Rhinosporidium
Rhinosporidiosis presents clinically as a mass growing on the nasal respira-
tory lining, often causing nasal obstruction. These growths may occur on
other mucosal surfaces, including the ocular conjunctivae, and can occur in
animals other than humans. The diagnosis is usually established by histologic
examination and by clinical presentation. Tissue sections are characterized
by inflammatory tissue embedding large round organisms (the trophocytes).
Members of Class Choanozoa are aquatic, and cases of human rhinospor-
idiosis can usually be associated with exposure to water in ponds, lakes, or
rivers. However, the organism, Rhinosporidium seeberi, has never actually
been isolated from these sources, nor has the organism been successfully cul-
tured. Because the organism has never been isolated from an aquatic reser-
voir, and has never been cultured, its taxonomic assignment has not been
easy. In the past, the organism was presumed to be fungal, as it looks some-
what like a large yeast on histologic cross-section. Molecular analysis places
the Rhinosporidium genus as a subclass within Class Choanozoa [85].
The geographic location with the highest incidence of rhinosporidiosis is
southern India and Sri Lanka. In general, the disease can be found in any tropical
region, and cases have been reported in the southeastern United States [85].
Rhinosporidiosis should not be confused with rhinoscleroma, a granulo-
matous lesion involving the nasal mucosa, caused by the bacteria, Klebsiella
rhinoscleromatis (Gamma Proteobacteria, Chapter 7).
Infectious species:
Rhinosporidium seeberi (rhinosporidiosis)
