Coccidioides immitis

Coccidioides immitis and C. posadasii are the pathogens of coccidioidomycosis. The natural habitat of Coccidioides immitis is the ground. There the hyphae decay into the infectious arthrospores.

The genus Coccidioides consists of two species: C. immitis and C. posadasii. In the past, it was believed that coccidioidomycosis was caused by a single species: C. immitis.

The arthrospores of Coccidioides immitis are inhaled with the dust. A primary coccidioidomycosis develops in the lungs of about 40 % of the exposed persons, which either heals spontaneously or becomes a focus for haematogenic spreading. The spores develop into spherules in the tissue. These sporangia-like fungal formations are surrounded by a thick capsule. They reach a size of 30-60 μm. Spherules are filled with numerous endospores. When the spherules burst, the endospores are released into the surrounding tissue. A new spherule can develop from each endospore (yard H 2019).

The pathogen, a dimorphic fungus, grows in dry to semi-arid alkaline soils throughout western North America and in Central and South America. Regions in the United States with the highest prevalence of the disease include California, Arizona and Texas. The Mexican states of Baja California, Coahuila, Sonora and Neuvo Leon currently have the highest positive results for skin testing.

Central America includes isolated endemic areas in Guatemala and Honduras. South America has isolated regions with high endemicity, including areas in Colombia, Venezuela, Argentina, Paraguay and Brazil. Although approximately 15,000 cases are reported annually in the United States, the actual burden of disease is estimated to be in the hundreds of thousands, as only California and Arizona reliably report and track disease (Kollath DR et al. 2019; Laniado-Laborín R et al. 2019). The risk of infection is particularly high during sandstorms. A transmission from person to person is not known.

S.u. coccidiodimycosis. About 60 % of all infections run inapparent or subclinical under the symptoms of a common cold. Clinically manifest courses of the disease lead to severe pneumonia with accompanying pleuritis and bloody sputum. A hematogenic spread with scattering in skin, subcutaneous fatty tissue, in bones and CNS are possible. Rarely is an infestation of the adrenal glands.

The typical sphaerulae are already found in the direct microscopic preparation when suitable examination material (sputum, bronchial secretion) is used.

Histology: Fungal structures can be detected in biopsy material with simple staining techniques (PAS).

Culture: Cultural detection is possible. The cultures are highly infectious.

PCR gives fast results.

Serology: Serological detection of antibodies is possible. However, in endemic areas, up to 80% of all people show antibodies as a sign of a previous, inapparent infection.

The initial stage of pulmonary coccidioidomycosis often heals spontaneously, which is why specific therapy is usually not necessary.

In clinically symptomatic pulmonary infection, itraconazole is the most commonly used drug (administration over months is necessary). Amphotericin B is the treatment of choice for severe and disseminated forms of the disease.

There is evidence of the use of C. immitis in aerosol form as a biological weapon (Deresinski S 2003).

1. Deresinski S (2003) Coccidioides immitis as a potential bioweapon. Semin RespirInfect 18:216-219.
2. Farm H (2019) Coccidioides immitis. In: Hof H, Schlüter D, Dörries R, ed. dual series Medical Microbiology. 7th, completely revised and extended edition. Stuttgart: Thieme; 2019. doi:10.1055/b-006-163249
3. Kollath DR et al (2019) The mysterious desert dwellers: Coccidioides immitis and Coccidioides posadasii, causative fungal agents of coccidioidomycosis. Virulence 10:222-233.
4. Laniado-Laborín R et al (2019) Coccidioidomycosis in Latin America. Med Mycol 57(Supplement 1):46-S55.
5. Viriyakosol S et al. (2019) APX001 and Other Gwt1 Inhibitor Prodrugs Are Effective in Experimental<i>Coccidioides immitis</i> Pneumonia. Antimicrobial agents Chemother 29:e01715-1718.