Draft of Conidiobolus coronatus (Costantin)Batko for 2010/2011 EOL University Species Pages Initiative by Grant Justin
Description status: Approved
(Latest review: 2010-12-17 10:22:44 EST (-0500) by Anne Pringle)
Conidiobolus coronatus is a ubiquitous saprobe of plant debris. It is an opportunistic pathogen and in humans it is the major causative agent of rhinoentomophthoromycosis. Rhinoentomophthoromycosis is the condition of having an Entomophthorales fungus in the nose. This word has four roots. Rhino comes from rhinos which meant nose in Greek. Entomophthoro comes from the fungal order Entomophthorales . Myco is Latin for fungus and sis stands for condition of.
C. coronatus has been known to parasitize other mammals, such as horses, llamas, dolphins, and chimpanzees. It was first described by Costantin in 1897 in France and was first isolated in 1961 by Chester Emmons and Charles Bridges from nasal granulomata of three horses in Australia. A granulomata is a bulge that forms because the cells of the immune system attempts to wall off the fungus. In 1965, Bras et al discovered and isolated the first human case in the Caribbean on the Grand Cayman Island.
C. coronatus is also an opportunistic parasite of many insects and it has been proposed as an insecticide. An insecticide is either a chemical or an organism that can kill insects that damage crops. C. coronatus infects a large variety of insects; however it is an especially effective parasite of Lepidoptera, which is the family that includes butterflies and moths.
C. coronatus lacks an apparent sexual life cycle because it is heterothallic and does not produce zygospores. However, the asexual life cycle is very complex. When, primary conidia are produced from the hyphae, the columella projects into the conidia. The primary conidia are released by an eversion mechanism which is characteristic of the genus Conidiobolus. Due to turgor pressure the conidia release and both the bottom of the conidia and the tip of the conidiophore project. The primary conidia are globose, multinucleate, and have two cells walls that are connected. The primary conidia can germinate by forming hyphae from multiple germ tubes. In addition, the primary conidia can germinate by repetitively forming into secondary conidia. The secondary conidia are oriented by light and are also released by eversion. There are various forms of secondary conidia. The primary conidia can produce short conidiophores containing microconidia which form on multiple sterigmata. The microconidia allow greater dispersal. In addition, there are various secondary resting spore types observed such as villose conidia, chlamydospores, and locriconidia. Resting spore allow survival in unfavorable growth conditions. C. coronatus is unique in its genus because it produces villose conidia, from which it gets its name because the spikes look like those of a crown, and microconidia. Oddly, when Costantin first described C. coronatus he did not observe the villose spores.
Secondary conidia production is regulated by the availability of nutrients and pH. Nutrient rich or mildly acidic or basic medium produces germination of germ tubes to form hyphae, while nutrient poor or extremely acidic and basic medium will lead to the production of secondary conidia. Younger cultures and cultures in humid environments tend to produce the microconidia, while older cultures tend to produce the villose conidia.
C. coronatus grows on potato dextrose, Sabouraud and cornmeal agar. The strains that are adapted to human infection readily grow at 37C. It produces flat waxy colorless to yellowish white to brownish tan cultures that form aerial mycelium. The colonies grow quickly and can reach a diameter of 6 cm in 48 hours. As a colony becomes older it may obtain a powdery texture and the lid of the petri dish will become covered in sticky conidia.
C. coronatus has wide vegetative coenoyctic hyphae that are 6 to 15 µm in size. The conidiophores are 8-12 µm in width by 60-90µm in length and they produce primary conidia that are 25 to 45 µm in diameter. Secondary spores tend to be smaller. The villose conidia’s spikes are 10 to 15 µm in length.
Conidiobolus coronatus is found on every continent. It was first isolated in plant detritus and is the most commonly isolated species of the genus Conidiobolus. Although, it prefers warmer, wetter, tropical and subtropical climates around the equator, it has been isolated in soil from the United Kingdom and eastern United States. The majority of the human infections occur in Western African rain forests in Nigeria, Cameroon, the Ivory Coast and Zaire. Interestingly, there are fewer cases of animal zygomycosis in these regions where human infection are more common. Infections have been documented in India, Colombia, Brazil, Jamaica, Coast Rica, the Congo, and the United States.
Although, C. coronatus is cosmopolitan, only about 150 cases of human disease have been observed. The fungus usually infects men that are agriculture or outdoor workers between the ages of 20-60. The male to female rate of infection is 8:1. The individuals that are infected are often immunocompromised, but in many cases the patients have been healthy with no physical abnormalities.
C. coronatus prefers warmer and wetter climates. There is a correlation between increased C. coronatus levels and the yearly peak of rainfall. In addition, it only germinates conidia in humidity greater than 95%, which is likely why disease is only observed in warmer, wetter, subtropical or tropical regions around the equator.
There are 27 species of the genus Conidiobolus. Only 19 species form zygospores and have a sexual cycle. All of the species have primary conidia and produce repetitive secondary conidia. However, the secondary conidia that are produced depend on the species. Microconidia have been observed in 10 species. All but six species have been originally isolated from plant detritus. Furthermore, C. coronatus, C. stromeides, and C. psuedococcus have been shown to infect insects.
There are three species of Entomophthorales that infect humans: Basidiobolus haptosporus, Conidiobolus coronatus, and Conidiobolus incongruus. The four diagnostic features of C. coronatus are production of microconidia and villose spores, projecting tips of the columella and the conidia after the eversion dispersal, and no production of zygospores.
C. incongruus very rarely causes disease. Unlike C. coronatus, C. incongruus is seldom isolated from the environment. It does not produce villose resting spores. It is characterized by production of microconidia, and it is homothallic and produces zygospores that lack a beak.
Basidiobolus haptosporus is characterized by very special shaped cylindrical conidiophores that form from the primary conidia during repetitive conidia production. They also have a sexual cycle in which they form distinctive beaked zygospores. In addition, they produce secondary conidia called capillospores with a sticky end. The sticky end is used to attach to insects for the dispersal of the spores.
Rhinoentomophthoromycosis caused by C. coronatus results from the inhalation of fungal spores that then implant in the nasal mucosa. The fungus then spreads throughout the subcutaneous of the face and can infect the paranasal sinuses. In certain case studies, it appeared that nose picking had led to small sores that became infected by the fungus! Mothers are always right! The lesions are painless and form nodules in the subcutaneous throughout the face. These nodules can cause the individual to look like a hippopotamus. If there is swelling inside the nasal cavity, it can lead to the sensation of nasal obstruction. However, the disease never passes the blood-brain barrier or into the lungs and thus in only a couple cases did it cause human death. The few case-studies of Bras et al 1965, Segura et al 1981, Costa et al 1991, and Do Valle et al 2001 are included in the works cited, for the readers that are interested in viewing pictures or reading case studies of the disease.
The excretion of serine proteases that are produced when the conidia are released is the most important virulence factor of C. coronatus. The serine proteases are excreted into the subcutaneous space, where they cause the release of amino acids by degrading proteins. This mode of virulence is postulated because there is an increase in the production of serine proteases during columella and conidia formation. C coronatus also produces tissue destroying collagenases and lipases.
The anti-fungal treatment for C. coronatus can vary from patient to patient because the drugs have varying success. Potassium iodide, septrin, amphotericin B, ketoconazole and intraconazole are the drugs that have been used most commonly.
There has been speculation on the use of C. coronatus as a control of insect pests that destroy crops. C. coronatus parasitizes a wide variety of insects however the family Lepidoptera is especially susceptible. It infects Galleria mellonella or Honeycomb Moth larvae that are pest of commercial honey or fig production and Bemisia tabaci or sweetpotato whitefly that damages sweetpotatoes. It can also infect Hylotrupes bajalus, wood-boring beetles, Calandaria granaria, grain weevils, Tenebrio molitor, mealworms, Spodoptera littoralis, the Egyption Cotton Leafworm and Dendrolimus pini, the pine-tree lappet.
Fungal infections of insect hosts are usually through the penetration of the insect exoskeleton. Once it has pierced through the exoskeleton, C. coronatus is a rapid killer. It takes 1-2 days to kill its host. A fungus can kill an insect via tissue destruction, production of mycotoxins, or depletion of nutrients. In infections caused by C. coronatus, mycotoxins are the cause of insect death. As C. coronatus spreads in the insect, it produces mycotoxins made of proteins. These mycotoxins cause damage to the muscles, however oddly the fat storage of the insects is not affected. In infected G. mellonella the infected sites became darker due to the production of melanin. After killing the host, C. coronatus will develop saphrophytically.
However, a disadvantage of C. coronatus for use as an insecticide is demonstrated by its infection of the pea aphid or Acyrthosiphon pison. Unlike the famous genus Cordyceps, C. coronatus cannot control its host’s behavior. The aphid releases its proboscis from its host plant and falls to the ground. C. coronatus then has limited its chance of dispersal to new hosts, because it will sporulate on the ground far away from the pea aphid colonies.
1. Batko A, Phylogenesis and taxonomic structure of the Entomophthoraceae. Ewolucja Biologiczna: Szkice teoretyczne i metodologiczne(C. Nowinski, ed.), Polska Akademia Nauk, Instytyt Filozofii i Socjologii. Warsaw: Ossolineum. 209-305. (1974)
2. Bogus MI and Schell K, Extracation of an insecticidal protein fraction from the parasitic fungus Conidiobolus coronatus (Entomophthorales). Acta parasitologica 47: 48-54 (2002)
3. Bogus MI and Szezepanik M, Histophathology of Conidiobolus coronatus (Entomophthoinfection) in Galleria mellonella (Lepidoptera) larvae. Acta parasitolgica 45: 48-54 (2000)
4. Bras G, Gordon CC, Emmons CW, Prendegast KM and Sugar M, A case of phycomycosis observed in Jamaica; infection with Entomophthora Coronata. Am. J. Trop. Med. Hyg. 14: 141-145 (1965)
5. Costa AR, Porto E, Pegas JRP, dos Reis VMS, Pires MC, da Silva Lacaz C, Rodrigues MC, Muller H and Cuce LC, Rhinofacial zygomycosis caused by Conidobolum coronatus. Mycopathologia 115:1-8 (1991)
6. Deshpande MV, Proteinases in fungal morphogenesis. World Journal of Microbiology and Biotechnology 8: 242-250 (1992)
7. Do Valle ACF, Wanke B, Lazera MDS, Monteiro PCF and Viegas MDL, Entomophtoramycosis by Conidiobolus coronatus. Report of a Case successfully treated with the combination of intraconazole and fluconazole. Rev. Inst. Med. Trop. S. Paulo 43: 233-236 (2001)
8. Emmons CW and Bridges CH, Entomophthora cornata, the Etiologic Agent of a phycomycosis of horses. Mycologia 53: 307-312 (1961)
9. Gindin G and Ben Ze’ev, Natural occurrence of and inoculation experiments with Conidiobolus coronatus and Conidobolus sp. in glasshouse populations of Bemisia tabaci. Phytoparasitica 22: 187-208 (1994)
10. Gugnani HC, Entomophtoromycosis due to Conidiobolus. Eur. J. Epidemiol. 8: 391-396 (1992)
11. Keller S and Zimmermann G, Mycopathogens of soil insects. In Insect-fungus interactions, ed. Wilding N, Collins NM, Hammond PM and WebberJF. London:Academic Press. 205-239 (1989)
12. King DS, Systematics of Conidiobolus (Entomophthorales) using numerical taxonomy. I. Biology and cluster analysis. Canad. J. Bot. 54: 45-65 (1976)
13. King DS, Systematics of Conidiobolus (Entomophthorales) using numerical taxonomy. III. Descriptions of recognized species. Canad. J. Bot. 55: 718-729. (1977)
14. King DS, Systematics of Fungi causing Entomophthoramycosis. Mycologia 71: 731-745. (1979)
15. King DS, Entomophthorales. In: Fungi Pathogenic for Humans and Animals, Part A: Biology. eds, Howard DH and Howard LF. New York: Marcel Dekker. 61-72. (1983)
16. Page RM and Humber RA, Phototropism in Conidiobolus coronatus. Mycologia 65: 335-354 (1973)
17. Ribes JA, Vanover-Sams CL and Baker DJ, Zygomycetes in Human Disease. Clinical Microbiology Reviews 13:236-301 (2000)
18. Segura JJ, Gonzalez K, Berrocal J and Marin G, Rhinoentomophthoromycosis: Report of the first two caes observed in Coast Rica (Central America), and review of the literature. Am. J. Trop. Med. Hyg. 30: 1078-1084 (1981)
19. Webster J and Weber RWS, Introduction to Fungi. Third Edition. Cambridge, UK: Cambridge University Press. 208-211 (2007)
20. Taxonomy of Conidiobolus coronatus http://www.ncbi.nlm.nih.gov/...
Conidiobolus coronatus (Cost.) Batko, Entomophaga, Mem. Hors. Ser. 2:129. 1964.
= Boudierella coronata Costantin, Bull. Soc. Mycol. France 13: 40. 1897.
=Delacroixia coronata (Cost.) Sacc. & Syd., Syll. Fung. 14: 457. 1899.
=Entomophthora coronata (Cost.) Kevork., J. Agric. Univ. Puerto Rico 21: 198. 1937.
= Conidiobolus coronatus (Cost.) Srin. & Thirum. Mycopathol. Mycol. Appl. 24: 296. 1964. –
= Conidiobolus (subgen. Delacroixia) coronatus (Cost.) Tyr-rell & MacLeod, J. Invert. Pathol. 20: 12. 1972.
=Conidiobolus villosus. Martin, Bot. Gaz. (Crawfordsville) 80: 317. 1925.
Description author: Grant Justin (Request Authorship Credit)
Created: 2010-11-02 21:08:31 EDT (-0400) by Grant Justin (b57d955)
Last modified: 2010-12-12 09:45:56 EST (-0500) by Grant Justin (b57d955)
Viewed: 218 times, last viewed: 2013-05-21 05:39:01 EDT (-0400)