Coccidioides

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Coccidioides
Spherule and endospore forms of Coccidioides immitis 01ee057 lores.jpg

Coccidioides

Systematics
Subdivision : Real ascent mushrooms (Pezizomycotina)
Class : Eurotiomycetes
Subclass : Eurotiomycetidae
Order : Onygenales
Family : Onygenaceae (Onygenaceae)
Genre : Coccidioides
Scientific name
Coccidioides
GW Stiles

Coccidioides is a genus of mushrooms from the group of ascomycota mushrooms . There are currently twoknown species that can only be distinguished from one another on the genetic level and on the basis of some physiological characteristics. As pathogenic fungi, they cancause coccidioidomycosis or coccidioidosisin humans and other mammals. In addition to this parasitic stage, they have a stage in which they are in the mostly dry sandy soil (saprophytic stage).

features

The two species of the genus, C. immitis and C. posadasii, are morphologically identical and can only be distinguished on the basis of genetic and epidemiological properties. In both species, only minor fruit forms ( anamorphs ) are known to date , while main fruit forms ( teleomorphs ) have either not yet been identified or do not exist.

Both types have two morphologically different forms ( dimorph ), which develop due to different thermal environments. On the one hand, there is a saprophytic stage, which lives mainly in the soil with average temperatures of 22 ° C, and a parasitic stage in the body of mammals at constant temperatures of 37 ° C (in humans) or correspondingly increased temperatures in rodents or other mammals. The saprophytic stage forms a white-gray mycelium in the soil with arthrospores . The parasitic stage, on the other hand, forms 20 to 80 micrometers large, double-contoured cells that grow into spherules ( sporangia ) with endospores.

distribution

Coccidioides species are restricted to the arid regions of North and South America and have regional endemic occurrences here. C. immitis is mainly found in California and there in the region of the San Joaquin Valley , the valley region on the San Joaquin River . In the desert regions of the southwestern United States and Mexico, the occurrence of both species overlap with a very high degree of probability (exact studies are not available) and the range of C. posadasii extends beyond that into the arid regions of South America.

Both species colonize dry and alkaline soils in desert and steppe regions. The fungi can be isolated to a comparatively high density, especially in rodent burrows.

pathology

Changes in the lungs caused by coccidioidomycosis . The tissue forms large cheese-like knots.

See main article Coccidioidomycosis

The Coccidioides species are the causative agents of coccidioidomycosis , also known as the San Joaquin Valley Fever or valley fever due to an epidemic in the San Joaquin Valley , California . This mycosis is caused by inhalation of arthrospores and manifests itself accordingly mainly in the trachea and lungs. As a primary infection , it has a flu-like course, and various autoimmune or allergy effects such as erythema nodosum , erythema exudativum multiforme and arthralgia known as "desert rheumatism" can be observed. As a rule, healing occurs spontaneously , but after dissemination , granulomatous or tuberculosis-like effects can occur on internal organs, the skin, the skeleton and the central nervous system , which can be fatal.

About 100,000 primary infections are found in the United States each year. Due to immunodeficiency diseases, especially AIDS, there is a clear increase in the disseminated form. The disseminated form is treated with amphotericin B (e.g. Amphocil).

Systematics

Internal system

Until 2002, Coccidioides was considered a monotypical genus with Coccidioides immitis, i.e. a genus with only one contained species. Although it had been known for several years that there are two genetically different types that can also be epidemiologically differentiated, these were only referred to as Subtypes California (CA) C. immitis and non-California (non-CA) C. immitis considered . In 2002, the non-Californian type was described as a separate species under the name Coccidioides posadasii on the basis of genetic data. To reliably differentiate the species, the working group identified two microsatellites in the genome of both species and determined different growth rates on substrates with high salt concentrations.

Fossil record

Although fungi are only very rarely found in fossil form and clearly identifiable diseases can only rarely be detected, there is a clear fossil record for coccidioidomycosis caused by Coccidioides immitis . This was carried out histologically on bison pines from the Holocene 8,500 years ago in Nebraska .

Popular culture

Pueblos of the Anasazi

Coccidioides immitis plays a central role in the novel Thunderhead by the writer duo Douglas Preston and Lincoln Child . The fungus is described there as an important component of the deadly powdered corpse of Indian sorcerers. The protagonists of the novel, a group of archaeologists, are confronted with the mushrooms and corpse powder in the legendary city of Quivira , one of the Seven Cities of Gold of the Anasazi . One of the archaeologists introduces the mushroom and explains the sudden fall of the Pueblo city:

A large number of Coccidioides imitis is found in the dust of Quivira. (...) I believe that the priests of Quivira infected prisoners or slaves with coccidioidomycosis, waited for them to die, and then made corpse powder out of their bodies. (...) but in the end they too fell victim to the deadly fungal spores. The light earthquake that damaged the towers and triggered the rock slide kicked up a cloud of dust similar to that in San Joaquin. However, here, in this narrow valley, the spores could not spread. They floated into the alcove and sat down in high concentration on the city.

supporting documents

Evidence cited

  1. ↑ a b Keyword “Coccidioides immitis” in: Pschyrembel. Medical dictionary. 257th edition, Nikol Verlagsgesellschaft mbH, Hamburg 21993. ISBN 3-933203-04-X
  2. ↑ MC Fisher, GL Koenig, TJ White, JW Taylor: Molecular and phenotypic description of Coccidioides posadasii sp. nov., previously recognized as the non-California population of Coccidioides immitis . Mycologia 94 (1), 2002; Pp. 73-84
  3. ↑ Willard Morrow: Holocene coccidioidomycosis: Valley Fever in early Holocene bison (Bison antiquus) . Mycologia 98 (5), 2006; Pp. 669-677.
  4. ↑ Douglas Preston , Lincoln Child : Thunderhead - Abyssal Abyss. Translation by Thomas A. Merk, Droemersche Verlagsanstalt Th. Knaur Nachf., Munich 2001; Pp. 431-435. ISBN 3-426-62158-4 .

literature

Web links

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