Rhinosporidium seeberi
Encyclopedia
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. It is most commonly found in tropical areas, especially India and Sri Lanka.
The pathogen was first identified in 1892, and was comprehensively described in 1900 by Seeber.
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 delay 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. The organism has been reported to be isolated and cultured in vitro
successfully at Kerala University, India by Dr. V. Thankamani in 2005. The isolated pathogenic organism believed to be Rhinosporidium seeberi was given the name "UMH.48." It was originally isolated from the biopsies and nasal swabs of Rhinosporidiosis patients. 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 Synchytridium endobioticum, a lower aquatic fungus that causes black wart disease in potatoes.
Incompletely resolved aspects of the disease, such as its epidemiology and pathogenesis, are expected to be understood in detail soon.
or a protist
), but recent research shows that it is part of a group called the Mesomycetozoea
(or "DRIP clade"), which includes a number of well-known fish pathogens such as Dermocystidium
and the Rosette Agent. The Mesomycetozoea is neither part of the fungi nor of animal
s, but diverged from them close to the time when they diverged from each other.
Rhinosporidium is generally classified as having na single species, although there is some evidence that different host species may be infected by different strains.
and Sri Lanka
: per capita, Sri Lanka has the highest incidence in the world. The disease is also found in other parts of the world.
An all-India survey conducted in 1957 found that this disease was absent from the states of Jummu & Kashmir
, Himachal Pradesh
, Punjab
, Haryana
and the North Eastern states of India. In Tamil Nadu
, 4 endemic areas were identified in the survey - (Madurai
, Ramnad, Rajapalayam
and Sivaganga
). The common denominator found in these areas was the practice of bathing in common ponds.
Demellow postulated that while bathing in common ponds, the nasal mucosa came into contact with infectious material. Karunarathnae proposed that the satellite lesions in skin and conjunctival mucosa arose as a result of auto inoculation.
It is presumed that because of its relationship to fish pathogens, Rhinosporidium evolved from aquatic pathogens similar to the other Mesomycetozoea
and evolved to infect mammal and bird hosts. It is not known if this happened once or more than once.
form inside living tissues. Recent studies done using Fluorescent in-situ-hybridization techniques provide evidence that its natural habitat is reservoir water, and, perhaps, soil contaminated with this water.
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.
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.
A novel method for the determination of the viability of rhinosporidial endospores by MTT-reduction led to the study of the sensitivity of endospores to biocides and anti-microbial
drugs (paper in preparation for submission).
This organism infects the mucosa of the nasal cavity
producing a mass like lesion. This mass appears to be polypoidal in nature with a granular surface speckled with whitish spores. The rhinosporidial mass has been classically described as a strawberry like mulberry mass. This mass may extend from the nasal cavity into the nasopharynx and present itself in the oral cavity
. These lesions commonly cause bleeding from the nasal cavity.
Rhinosporidium seeberi can also affect the lacrimal gland
and also rarely the skin and genitalia.
Common sites affected:
Povidone-iodine and anti-fungal drugs like amphotericin-B, Dapsone
and silver nitrate
have been suggested as possible antiseptics.
Eukaryote
A eukaryote is an organism whose cells contain complex structures enclosed within membranes. Eukaryotes may more formally be referred to as the taxon Eukarya or Eukaryota. The defining membrane-bound structure that sets eukaryotic cells apart from prokaryotic cells is the nucleus, or nuclear...
pathogen responsible for rhinosporidiosis
Rhinosporidiosis
-Classification:This organism was previously considered to be a fungus, and rhinosporidiosis is classified as a fungal disease under ICD-10.It is now considered to be a parasite, classified under Mesomycetozoea....
, a disease which affects humans, horses, dogs, and to a lesser extent cattle, cats, foxes, and birds. It is most commonly found in tropical areas, especially India and Sri Lanka.
The pathogen was first identified in 1892, and was comprehensively described in 1900 by Seeber.
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 delay at in vitro
In vitro
In vitro refers to studies in experimental biology that are conducted using components of an organism that have been isolated from their usual biological context in order to permit a more detailed or more convenient analysis than can be done with whole organisms. Colloquially, these experiments...
culture and establishment of disease in experimental animals and hence paucity of information on its sensitivity to drugs, and the immunology of the pathogen. The organism has been reported to be isolated and cultured in vitro
In vitro
In vitro refers to studies in experimental biology that are conducted using components of an organism that have been isolated from their usual biological context in order to permit a more detailed or more convenient analysis than can be done with whole organisms. Colloquially, these experiments...
successfully at Kerala University, India by Dr. V. Thankamani in 2005. The isolated pathogenic organism believed to be Rhinosporidium seeberi was given the name "UMH.48." It was originally isolated from the biopsies and nasal swabs of Rhinosporidiosis patients. 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 Synchytridium endobioticum, a lower aquatic fungus that causes black wart disease in potatoes.
Incompletely resolved aspects of the disease, such as its epidemiology and pathogenesis, are expected to be understood in detail soon.
Phylogeny
For most of the 20th century, the classification of R. seeberi was unclear (being considered either a fungusFungus
A fungus is a member of a large group of eukaryotic organisms that includes microorganisms such as yeasts and molds , as well as the more familiar mushrooms. These organisms are classified as a kingdom, Fungi, which is separate from plants, animals, and bacteria...
or a protist
Protist
Protists are a diverse group of eukaryotic microorganisms. Historically, protists were treated as the kingdom Protista, which includes mostly unicellular organisms that do not fit into the other kingdoms, but this group is contested in modern taxonomy...
), but recent research shows that it is part of a group called the Mesomycetozoea
Mesomycetozoea
The Mesomycetozoea are a small group of protists, mostly parasites of fish and other animals.-Significance:...
(or "DRIP clade"), which includes a number of well-known fish pathogens such as Dermocystidium
Dermocystidium
Dermocystidium is a genus of cyst forming parasitic protists of fish, which are the causative agents of dermocystidiosis.- Taxonomic History :...
and the Rosette Agent. The Mesomycetozoea is neither part of the fungi nor of animal
Animal
Animals are a major group of multicellular, eukaryotic organisms of the kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life. Most animals are motile, meaning they can move spontaneously and...
s, but diverged from them close to the time when they diverged from each other.
Rhinosporidium is generally classified as having na single species, although there is some evidence that different host species may be infected by different strains.
Epidemiology
Infection with this organism has been reported from ~70 countries, with the majority of cases (95%) reported from IndiaIndia
India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...
and Sri Lanka
Sri Lanka
Sri Lanka, officially the Democratic Socialist Republic of Sri Lanka is a country off the southern coast of the Indian subcontinent. Known until 1972 as Ceylon , Sri Lanka is an island surrounded by the Indian Ocean, the Gulf of Mannar and the Palk Strait, and lies in the vicinity of India and the...
: per capita, Sri Lanka has the highest incidence in the world. The disease is also found in other parts of the world.
An all-India survey conducted in 1957 found that this disease was absent from the states of Jummu & Kashmir
Kashmir
Kashmir is the northwestern region of the Indian subcontinent. Until the mid-19th century, the term Kashmir geographically denoted only the valley between the Great Himalayas and the Pir Panjal mountain range...
, Himachal Pradesh
Himachal Pradesh
Himachal Pradesh is a state in Northern India. It is spread over , and is bordered by the Indian states of Jammu and Kashmir on the north, Punjab on the west and south-west, Haryana and Uttar Pradesh on the south, Uttarakhand on the south-east and by the Tibet Autonomous Region on the east...
, Punjab
Punjab (India)
Punjab ) is a state in the northwest of the Republic of India, forming part of the larger Punjab region. The state is bordered by the Indian states of Himachal Pradesh to the east, Haryana to the south and southeast and Rajasthan to the southwest as well as the Pakistani province of Punjab to the...
, Haryana
Haryana
Haryana is a state in India. Historically, it has been a part of the Kuru region in North India. The name Haryana is found mentioned in the 12th century AD by the apabhramsha writer Vibudh Shridhar . It is bordered by Punjab and Himachal Pradesh to the north, and by Rajasthan to the west and south...
and the North Eastern states of India. In Tamil Nadu
Tamil Nadu
Tamil Nadu is one of the 28 states of India. Its capital and largest city is Chennai. Tamil Nadu lies in the southernmost part of the Indian Peninsula and is bordered by the union territory of Pondicherry, and the states of Kerala, Karnataka, and Andhra Pradesh...
, 4 endemic areas were identified in the survey - (Madurai
Madurai
Madurai is the third largest city in the Indian state of Tamil Nadu and one of the oldest continuously inhabited cities in the world. It served as the capital city of the Pandyan Kingdom. It is the administrative headquarters of Madurai District and is famous for its temples built by Pandyan and...
, Ramnad, Rajapalayam
Rajapalayam
Rajapalayam is a town and a special grade municipality in Virudhunagar district in the Indian state of Tamil Nadu. It is located 85 km southwest of Madurai in the state of Tamil Nadu. Its main attractions are the Ayyanar Falls and the neighbour town of Srivilliputtur...
and Sivaganga
Sivaganga
Sivaganga, also known as Sivagangai, is a town and a municipality in Sivaganga district in the Indian state of Tamil Nadu. It is the administrative headquarters of Sivaganga district.-Geography:...
). The common denominator found in these areas was the practice of bathing in common ponds.
Transmission and Dissemination
- Demellow's theory of infection
- Karunarathnae's autoinoculation theory
- Haematogenous spread - to distant sites
- Lymphatic spread - causing lymphadenitis (rare)
Demellow postulated that while bathing in common ponds, the nasal mucosa came into contact with infectious material. Karunarathnae proposed that the satellite lesions in skin and conjunctival mucosa arose as a result of auto inoculation.
It is presumed that because of its relationship to fish pathogens, Rhinosporidium evolved from aquatic pathogens similar to the other Mesomycetozoea
Mesomycetozoea
The Mesomycetozoea are a small group of protists, mostly parasites of fish and other animals.-Significance:...
and evolved to infect mammal and bird hosts. It is not known if this happened once or more than once.
Natural habitat
Karunarathnae also proposed that Rhinosporidium existed in a dimorphic state - a saprotroph in soil and water and a yeastYeast
Yeasts are eukaryotic micro-organisms classified in the kingdom Fungi, with 1,500 species currently described estimated to be only 1% of all fungal species. Most reproduce asexually by mitosis, and many do so by an asymmetric division process called budding...
form inside living tissues. Recent studies done using Fluorescent in-situ-hybridization techniques provide evidence that its natural habitat is reservoir water, and, perhaps, soil contaminated with this water.
Pathology
One report indicates that patients with rhinosporidiosis possess anti-R. seeberi IgGImmunoglobulin G
Immunoglobulin G are antibody molecules. Each IgG is composed of four peptide chains — two heavy chains γ and two light chains. Each IgG has two antigen binding sites. Other immunoglobulins may be described in terms of polymers with the IgG structure considered the monomer.IgG constitutes 75%...
to an inner wall antigen
Antigen
An antigen is a foreign molecule that, when introduced into the body, triggers the production of an antibody by the immune system. The immune system will then kill or neutralize the antigen that is recognized as a foreign and potentially harmful invader. These invaders can be molecules such as...
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.
Humoral and Cell-mediated Immune responses
Immune system
An immune system is a system of biological structures and processes within an organism that protects against disease by identifying and killing pathogens and tumor cells. It detects a wide variety of agents, from viruses to parasitic worms, and needs to distinguish them from the organism's own...
in human patients and in experimental mice have been defined; several mechanisms of immune evasion by R. seeberi have been identified.
A novel method for the determination of the viability of rhinosporidial endospores by MTT-reduction led to the study of the sensitivity of endospores to biocides and anti-microbial
Antimicrobial
An anti-microbial is a substance that kills or inhibits the growth of microorganisms such as bacteria, fungi, or protozoans. Antimicrobial drugs either kill microbes or prevent the growth of microbes...
drugs (paper in preparation for submission).
Clinical features
Nasal cavity
The nasal cavity is a large air filled space above and behind the nose in the middle of the face.- Function :The nasal cavity conditions the air to be received by the other areas of the respiratory tract...
producing a mass like lesion. This mass appears to be polypoidal in nature with a granular surface speckled with whitish spores. The rhinosporidial mass has been classically described as a strawberry like mulberry mass. This mass may extend from the nasal cavity into the nasopharynx and present itself in the oral cavity
Mouth
The mouth is the first portion of the alimentary canal that receives food andsaliva. The oral mucosa is the mucous membrane epithelium lining the inside of the mouth....
. These lesions commonly cause bleeding from the nasal cavity.
Rhinosporidium seeberi can also affect the lacrimal gland
Lacrimal gland
The lacrimal glands are paired almond-shaped glands, one for each eye, that secrete the aqueous layer of the tear film. They are situated in the upper, outer portion of each orbit, in the lacrimal fossa of the orbit formed by the frontal bone. Inflammation of the lacrimal glands is called...
and also rarely the skin and genitalia.
Common sites affected:
- Nose - 78%
- Nasopharynx - 68%
- Tonsil - 3%
- Eye - 1%
- Skin - very rare
Treatment
Treatment is generally by surgical removal of the infected tissues.Povidone-iodine and anti-fungal drugs like amphotericin-B, Dapsone
Dapsone
Dapsone is a medication most commonly used in combination with rifampicin and clofazimine as multidrug therapy for the treatment of Mycobacterium leprae infections . It is also second-line treatment for prophylaxis against Pneumocystis pneumonia caused by Pneumocystis jiroveci Dapsone...
and silver nitrate
Silver nitrate
Silver nitrate is an inorganic compound with chemical formula . This compound is a versatile precursor to many other silver compounds, such as those used in photography. It is far less sensitive to light than the halides...
have been suggested as possible antiseptics.