Equis ISSN 2398-2977

Coccidioides immitis

Contributor(s): Richard Walker




  • Dimorphic fungus.
  • Genus:Coccidioides.
  • Species:immitis.

Active Forms

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Clinical Effects



  • C. immitisinhabits the soil in the Lower Sonoran Life Zone.
  • High prevalence is associated with an annual rainfall of 125-500 mm and mean summer and winter temperatures of more than 27°C/80.5°F and 7°C/44.5°F respectively.


  • Arthroconidia grow into spherules in tissue.
  • The spherule wall disintegrates and endospores are liberated and produce new spherules in tissue.
  • On a non-living substrate, endospores develop into mycelial growth.


  • Inhalation of dust.
  • Primary cutaneous infection (rare).

Pathological effects

  • Cell-mediated immunity develops early and can persist indefinitely and indicates resistance; disappears in disseminated disease.
  • IgM appears initially and then disappears.
  • IgG titers rise in disseminated disease and remain high until after recovery.
  • Primarily a disease of the lungs and secondarily a disease of bones and other organs.
  • Inflammatory response occurs but phagocytes unable to kill the arthroconidia. They are carried to the lymph nodes where other inflammatory foci occur. Usually arrested at this stage if cell-mediated immunity is not compromised, otherwise dissemination occurs.
  • Dogs: lassitude, anorexia, cough, fever, lameness, discharging sinuses. Some cases may be mild or subclinical.
  • Horses: most cases are subclinical. Has been reported to cause abortion   Abortion: overview  , mastitis   Mammary gland: mastitis  and osteomyelitis   Spine: osteomyelitis  (see references).

Other Host Effects

  • Disease occurs in dogs, cats, horses and humans; subclinical in other animals.


Control via chemotherapies


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Further Reading


Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Higgins J C, Leith G S, Voss E D & Pappagianis D (2005) Seroprevalence of antibodies against Coccidoides immitis in healthy horses. JAVMA 226 (11), 1888-1891 PubMed.
  • Stoltz J H et al (1994) Coccidioides immitis abortion in an Arabian mare. Vet Pathol 31 (2), 258-259 PubMed.
  • Chapman S W & Daniel C R (1994) Cutaneous manifestations of fungal infections. Infect Dis Clin North Am (4), 879-910 PubMed.
  • Walker R L (1993) Coccidioides immitis mastitis in a mare. J Vet Diagn Invest (3), 446-448 PubMed.
  • Foley J P et al (1992) Treatment of coccidioidomycosis osteomyelitis with itraconazole in a horse. A brief report. J Vet Intern Med (6), 333-334 PubMed.
  • Ziemer E L et al (1992) Coccidioidomycosis in horses - 15 cases (1975-1984). JAVMA 201 (6), 910-916 PubMed.
  • Sekkon A S et al (1991) Review of human and animal cases of coccidioidomycosis diagnosed in Canada. Mycopathologica 113, 1 PubMed.