Rhinosporidium seeberi

Rhinosporidium seeberi is a eukaryotic pathogen responsible for rhinosporidiosis, a disease which affects humans, horses, dogs, and to a lesser extent cattle, cats, foxes, and birds.

These include the pathogen’s natural habitat, some aspects of its ‘lifecycle’, its immunology, some aspects of the epidemiology of the disease in humans and in animals, the reasons for the delay at in vitro culture, and establishment of disease in experimental animals, hence paucity of information on its sensitivity to drugs, and the immunology of the pathogen.

The various developmental stages of UMH.48 showed a strong resemblance with the structures seen in hisopathological sections of rhinosporidiosis in tissue samples.

The spores of UMH.48 were found to be viable even after a decade of preservation in the refrigerator without any subculture, resembling the features of Synchytrium endobioticum, a lower aquatic fungus that causes black wart disease in potatoes.

For most of the 20th century, the classification of R. seeberi was unclear (being considered either a fungus or a protist), but it was shown to be part of a group called the Mesomycetozoea[8][9] (or "DRIP clade"),[10] which includes a number of well-known fish pathogens such as Dermocystidium and Sphaerothecum destruens.

[12] Karunarathnae also proposed that Rhinosporidium existed in a dimorphic state—a saprotroph in soil and water and a yeast form inside living tissues.

[15] One report indicates that patients with rhinosporidiosis possess anti-R. seeberi IgG to an inner wall antigen expressed only during the mature sporangial stage.