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 fromPubMed.
  • Higgins J C, Leith G S, Voss E D & Pappagianis D (2005)Seroprevalence of antibodies againstCoccidoides immitisin healthy horses.JAVMA226(11), 1888-1891PubMed.
  • Stoltz J Het al(1994)Coccidioides immitisabortion in an Arabian mare.Vet Pathol31(2), 258-259PubMed.
  • Chapman S W & Daniel C R (1994)Cutaneous manifestations of fungal infections.Infect Dis Clin North Am8(4), 879-910.
  • Walker R L (1993)Coccidioides immitismastitis in a mare.J Vet Diagn Invest5(3), 446-448PubMed.
  • Foley J Pet al(1992)Treatment of coccidioidomycosis osteomyelitis with itraconazole in a horse. A brief report.J Vet Intern Med6(6), 333-334PubMed.
  • Ziemer E Let al(1992)Coccidioidomycosis in horses - 15 cases (1975-1984).JAVMA201(6), 910-916PubMed.
  • Sekkon A Set al(1991)Review of human and animal cases of coccidioidomycosis diagnosed in Canada.Mycopathologica113, 1PubMed.