[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Microbiology](https://durgical.com/en/microbiology/) › [Dimorphic fungi](https://durgical.com/en/microbiology/groups/dimorphic-fungi/) › Coccidioides immitis [Microbiology](https://durgical.com/en/microbiology/) · [Dimorphic fungi](https://durgical.com/en/microbiology/groups/dimorphic-fungi/) # Coccidioides immitis - Fungus - Exam priority: medium A soil fungus of the deserts of the Americas; inhaled with dust, it causes pneumonia, sometimes with skin nodules and joint pain. Updated 2026-11-01 Also called: Coccidioides posadasii, Valley fever, coccidioidomycosis ## Key points - Desert and dust: Valley fever - No yeasts: spherules with endospores - Erythema nodosum and joint pain - Lab hazard: culture at level 3 - Disseminates more in pregnancy, HIV and certain ancestries ## At a glance **Shape** Barrel-shaped arthroconidia in soil; large spherules full of endospores in tissue **Family** Onygenaceae (Onygenales) **Type** Dimorphic fungus: mold in soil, spherules in tissue **Stain** H&E, PAS and silver (GMS) in tissue; KOH on sputum **Size** Large spherules, about 20–80 µm ## Morphology - In soil: hyphae that break into barrel-shaped arthroconidia, alternating with empty cells - In tissue: thick-walled spherules - Mature spherules burst and release endospores ## Transmission - Inhaling arthroconidia with dust (wind, construction, digging, farming) - Laboratory infection from cultures (highly infectious in the lab) - Not spread from person to person **Reservoir:** Soil of arid and semi-arid areas ### Isolation precautions What the care team adds to standard precautions. - Standard ## Life cycle - In dry soil it grows as a mold and forms arthroconidia - Wind or digging lifts the arthroconidia, which are inhaled - In the lung each arthroconidium turns into a spherule - The mature spherule fills with endospores and bursts - Each endospore forms a new spherule and the infection spreads ## Virulence factors - Spherules are too large for a phagocyte to engulf - Glycoprotein-rich wall that modulates the immune response - Spread to skin, bone and meninges if cellular immunity fails ## Diseases it causes - Coccidioidomycosis: acute pneumonia, chronic lung disease and disseminated disease (skin, bone, meninges) [Endemic mycoses: blastomycosis and coccidioidomycosis →](https://durgical.com/en/conditions/endemic-mycoses-blastomycosis-and-coccidioidomycosis/) ## Clinical picture - Fever, cough, chest pain, fatigue and joint pain weeks after dust exposure - Erythema nodosum or erythema multiforme - Dissemination risk: pregnancy, HIV, transplant, diabetes and people of African or Filipino ancestry - Chronic meningitis in disseminated disease ## Diagnosis - Serology (IgM and IgG by immunoassay, immunodiffusion or complement fixation) - Spherules with endospores on biopsy or sputum - Culture only in a biosafety level 3 laboratory - PCR on respiratory samples ## Treatment Many mild pneumonias resolve on their own. Severe or disseminated disease or high-risk groups: azoles (fluconazole, itraconazole); amphotericin B in severe disease or in pregnancy. Drug class only; doses and regimens are set by the clinician from the current guideline. In Pharmacology: - [Fluconazole](https://durgical.com/en/pharmacology/fluconazole/) - [Itraconazole](https://durgical.com/en/pharmacology/itraconazole/) - [Amphotericin B](https://durgical.com/en/pharmacology/amphotericin-b/) ## Prevention - Reduce dust exposure in endemic areas (mask, wetting the soil) - Warn the laboratory when it is suspected, so the culture is handled with biosafety ## In Colombia Colombia is not a classic endemic area; it is considered after travel to or residence in arid parts of Mexico, Central America or South America. It is a frequent topic in international exams. ## Memory aid Cocci comes in a shell full of seeds: the spherule is a pod packed with endospores that bursts and plants more. ## Test yourself Think of the answer, then tap the question to see it. ## Which Coccidioides structure is seen in tissue instead of yeasts? Large thick-walled spherules full of endospores. ## Which form of the fungus is inhaled? The arthroconidia that form in dry soil and are lifted with dust. ## Why does Coccidioides culture require a biosafety level 3 laboratory? The mold in culture produces arthroconidia that disperse easily and infect staff. [Add to my cards (3)](https://durgical.app/estudiar/?add=/en/microbiology/coccidioides-immitis/) ## Related - [Histoplasma capsulatum](https://durgical.com/en/microbiology/histoplasma-capsulatum/) - [Blastomyces dermatitidis](https://durgical.com/en/microbiology/blastomyces-dermatitidis/) ## Related conditions - [Endemic mycoses: blastomycosis and coccidioidomycosis](https://durgical.com/en/conditions/endemic-mycoses-blastomycosis-and-coccidioidomycosis/) ## What the colours mean **Gram-positive** Thick peptidoglycan wall: stains purple. **Gram-negative** Thin wall with an outer membrane: stains pink. **Acid-fast** Lipid-rich wall (mycobacteria): Ziehl–Neelsen stain. [← Back to the group: Dimorphic fungi](https://durgical.com/en/microbiology/groups/dimorphic-fungi/) Educational content on microorganisms; not a treatment guide and no substitute for a health professional's advice. No doses are given. Sources: [About Valley Fever](https://www.cdc.gov/valley-fever/about/index.html) (CDC, 2024); [Clinical Overview of Valley Fever](https://www.cdc.gov/valley-fever/hcp/clinical-overview/index.html) (CDC, 2024). ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/microbiology/coccidioides-immitis/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/microbiology/coccidioides-immitis/