Rhinosporidium seeberi

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This disease was first identified in 1892 but was comprehensively described in 1900 by Seeber. It has been reported from about 70 countries of diverse characteristics, although its highest incidence has been in India and Sri Lanka; perhaps on a population basis, Sri Lanka has the higher incidence. Yet there are many aspects of the disease and of the pathogen Rhinosporidium seeberi which remain problematic and enigmatic. These include, the pathogen’s natural habitat, some aspects of its ‘life cycle’, its immunology, some aspects of the epidemiology of the disease in humans and in animals, the reasons for the failure at in vitro culture and establishment of disease in experimental animals and hence paucity of information on its sensitivity to drugs, and the immunology of the pathogen.

Incompletely resolved aspects of the disease are its epidemiology and its pathogenesis. (see review refs. 14, 15, 22).

Of interest was the report indicating that patients with rhinosporidiosis possess anti-R. seeberi IgG to an inner wall antigen expressed only during the mature sporangial stage. This finding suggests that the mapping of antigenic proteins may lead to important antigens with the potential as vaccine candidates (see ref. 1).

A recent breakthrough into R. seeberi’s phylogenetic affinities, using molecular tools, revealed that this enigmatic organism is closer to fish parasites in the Kingdom Protoctista. This monophyletic group was named the Mesomycetozoea and it includes organisms such as:- Dermocystidium, the Rosette Agent (causing disease in fish) and R. seeberi. (see refs. 2, 6, 13).

Humoral and Cell-mediated Immune responses in human patients and in experimental mice have been defined; several mechanisms of immune evasion by R. seeberi have been identified (see 9, 10, 16)

A novel method for the determination of the viability of rhinosporidial endospores by MTT-reduction (ref. 17) led to the study of the sensitivity of endospores to biocides (ref. 23) and anti-microbial drugs (in preparation for submission).

Some recent publications on rhinosporidiosis and R. seeberi

Herr, R.A.et al., 1999. Immunolocalization of an endogenous antigenic material of Rhinosporidium seeberi expressed only during mature sporangial development. FEMS. Immunology & Medical Microbiology. 23, 205-212.

Herr, R.A.et al., 1999. Phylogenetic analysis of Rhinosporidium seeberi’s 18S small subunit Ribosomal DNA groups this pathogen among members of the Protoctistan Mesomycetozoa Clade. J.Clinical Microbiology, Sept., 2750-2754.

Atapattu, D.N. et al., 1999. Purification of the endospores and sporangia of Rhinosporidium seeberi on Percoll columns. Mycopathologia, 1999, 145, 113-119.

Mendoza L et al., 1999. In vitro studies on the mechanisms of endospore release by Rhinosporidium seeberi, Mycopathologia, 148, 9-15

Arseculeratne, S.N. et al., 2000. Failure to infect congenitally immunodeficient mice SCID and NUDE mice with Rhinosporidium seeberi., Medical Mycology, 38; 393-395

Fredricks, D.N., Jolley, J.A., Lepps, P.W., Kosek, J.C. & Relman, D.A. 2000, Rhinosporidium seeberi: a human pathogen from a novel group of aquatic Protistan parasites, Emerging Infectious Diseases, 6(3), 273-282.

Arseculeratne S.N. 2001. Microcystis aeruginosa as the cause of rhinosporidiosis (letter). Mycopathologia, 151, 3-4.

Mendoza L et al. 2001. (reply to K.B.Ahluwalia's ideas on M. aeruginosa as the cause of rhinosporidiosis). J. Clinical Microbiology, 39(1), 413-415.

Sharmini Jayasekera. et al 2001, Cell-mediated immune responses to Rhinosporidium seeberi in mice, Mycopathologia, 152, 69-79.

de Silva N.R. et al. 2001 Cell-mediated immune responses in human rhinosporidiosis. Mycopathologia 152, 59-68.

Arseculeratne S.N. et al. 2001 Lymphadenitis, trans-epidermal elimination and unusual histopathology in human rhinosporidiosis. Mycopathologia, 153, 57-69. (This is the first report on lymphadenitis in rhinosporidiosis)

Appuhamy, S, Atapattu, D.N., Arseculeratne, S.N. & Eriyagama, N.B. 2002, Strain variation in Rhinosporidium seeberi, Proceedings of the Sri Lanka College of Microbiologists, OP7.

Mendoza, L., Taylor, J.W. & Ajello, L. 2002, The Class Mesomycetozoea: A heterogeneous group of microorganisms at the Animal-Fungal boundary, Annual Rev. Microbiol., 56, 315-344.

Arseculeratne, S. N. & Atapattu, D. N. 2002, Recent advances in knowledge on Rhinosporidium seeberi and rhinosporidiosis. In: Fungi in human and animal health. R. K. S. Kushwaha ed., Jodhpur Scientific Publishers, India

Arseculeratne, S.N. 2002. Recent advances in Rhinosporidiosis and Rhinosporidium seeberi. Indian J. Medical Microbiol., 20(3), 119-131.

Arseculeratne, S. N. 2003, Mechanisms of immune evasion by Rhinosporidium

seeberi. Bulletin of the Sri Lanka College of Microbiologists, 1(1), 56-58. Arseculeratne, S. N. & Atapattu, D. N. 2004, The assessment of the viability of the

endospores of Rhinosporidium seeberi with MTT (3-[4, 5-dimethyl-2-thiazolyl]-2, 5

diphenyl-2H-tetrazolium bromide). Mycological Research, 108(12): 1423-1430.

Arseculeratne, S. N., Kumarasiri, P. V. R., Rajapakse, R. P. V. J., Perera, N. A. N. D.

Arseculeratne, G., & Atapattu, D. N. 2004, Anti-rhinosporidial antibody levels in patients with rhinosporidiosis and in asymptomatic persons in Sri Lanka. Mycopathologia, 158: 157-164.

Arseculeratne, S. N. 2005, Rhinosporidiosis – What is the cause? Current Opinion In Infectious Diseases, 18: 113-118.

Arseculeratne, S.N., Atapattu, D.N. & Wickramaratne, K. 2005, The nature and significance of the electron dense bodies of the endospores of Rhinosporidium seeberi: their reactions with MTT (3-[4, 5-dimethyl-2-thiazolyl]-2, 5-diphenyl-2H tetrazolium bromide). Medical Mycology, 43: 261-273.

Arseculeratne, S. N., Atapattu, D. N. & Eriyagama, N. B. 2005, Human anti rhinosporidial antibody does not cause metabolic inactivation or morphological damage in endopsores of Rhinosporidium seeberi, in vitro. Indian J. Medical Micobiol., 23(1)14-19.

Arseculeratne, S.N. & L. Mendoza. 2005. Rhinosporidium seeberi. In: Topley & Wilson’s Microbiology & Microbial Infections, 10th ed., vol.5, Medical Mycology, R.J. Hay & W. Merz, vol. Eds., London, Hodder-Arnold

Arseculeratne, S.N., Atapattu, D.N., Balasooriya, Pushpa & Fernando, R. 2006, The effect of biocides (antiseptics and disinfectants) on the endospores of Rhinosporidium seeberi. Indian J. Medical Microbiol. (in press)

Rhinosporidiosis Research Group
Concise information on Rhinosporidiosis