Course # DL-993: Coccidioidomycosis (Valley Fever: A Re-Emerging Mycosis)

by Lucy Treagan, Ph.D. - Prof. Biol. Emerita - University of San Francisco

Approved for 2.0 CE
Level of Difficulty: Intermediate

Abstract: Historical Background

The first reported case of coccidioidomycosis occurred in Argentina. In 1892 Alejandro Posadas, a medical intern in Buenos Aires, attended a patient who had severe ulcerative skin lesions and recurrent fever. The patient eventually died after suffering 7 years of progressive skin lesions. Skin biopsy specimens showed organisms that resembled protozoa, specifically coccidia that parasitize humans.

A year after this case was reported a patient was hospitalized in San Francisco with skin lesions resembling those of Posadas’ patient. The San Francisco patient was a manual laborer who lived and worked in the San Joaquin Valley. Clinical specimens from this patient showed organisms that resembled protozoa. The patient did not recover from his illness; he died several years later. Specimens from the patient were studied by Gilchrist, who was a pathologist at Johns Hopkins Medical School, as well as by Rixford, a San Francisco surgeon. In 1896 Gilchrist concluded that the organisms in the patient’s samples were protozoa and resembled Coccidia. The newly isolated pathogen was named Coccidioides (resembling Coccidia) immitis (not mild) by Gilchrist and Rixford.

Four years later William Ophuls and Herbert Moffitt cultured clinical material from a patient whose symptoms resembled the case described by Rixford and Gilchrist. Ophuls and Moffitt inoculated samples from this patient into male guinea pigs, producing orchitis (inflammation of the testes). Spherules could be observed microscopically in pus removed from the guinea pigs. When the spherule preparation was reexamined on the following day, mycelia had developed. Ophuls and Moffitt demonstrated that C. immitis was not a protozoan. It was a fungus that existed in mycelial form when cultured and as spherical protozoa-like bodies within tissues.

In 1929 a laboratory accident provided valuable information on transmission of coccidioidomycosis. Harold Chope, a medical student at Stanford, opened an old culture of C. immitis and inhaled the fungal spores. Chope developed severe pneumonia from which he recovered after several months of illness. Subsequently, when Harold Chope left Stanford, one of his classmates, Charles Smith, became involved in the coccidioidomycosis project. Later Charles Smith continued his research at the University of California Berkeley where he and his research group made invaluable contributions to the study of coccidioidomycosis. Smith’s work included development of skin test reagents, diagnostic serologic methods, epidemiological studies, investigation of clinical forms of disease, and studies of disease transmission (1).


After completing this course the participant will be able to:

  1. Discuss discovery and identification of Coccidioides as a fungal pathogen.
  2. Outline principal characteristics and life cycle of Coccidioides
  3. Describe classification of Coccidioides as a select agent.
  4. Outline epidemiology of Valley Fever (coccidioidomycosis).
  5. Discuss clinical forms of coccidioidomycosis.
  6. Summarize risk factors that contribute to disseminated coccidioidomycosis.
  7. List laboratory methods used for diagnosis of coccidioidomycosis.
  8. Explain the nature of immune response to Coccidioides infection.
  9. Outline treatment of coccidioidomycosis.
  10. Describe current state of vaccine development.
  11. List experimental models of coccidioidomycosis.

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