The mysterious desert dwellers: Coccidioides immitis and Coccidioides posadasii, causative fungal agents of coccidioidomycosis

Abstract

The genus Coccidioides consists of two species: C. immitis and C. posadasii. Prior to 2000, all disease was thought to be caused by a single species, C. immitis. The organism grows in arid to semiarid alkaline soils throughout western North America and into Central and South America. Regions in the United States, with highest prevalence of disease, include California, Arizona, and Texas. The Mexican states of Baja California, Coahuila, Sonora, and Neuvo Leon currently have the highest skin test positive results. Central America contains isolated endemic areas in Guatemala and Honduras. South America has isolated regions of high endemicity including areas of Colombia, Venezuela, Argentina, Paraguay, and Brazil. Although approximately 15,000 cases per year are reported in the United States, actual disease burden is estimated to be in the hundreds of thousands, as only California and Arizona have dedicated public health outreach, and report and track disease reliably. In this review, we survey genomics, epidemiology, ecology, and summarize aspects of disease, diagnosis, prevention, and treatment.

Keywords: comparative genomics; fungal pathogen; onygenales.

Figure 1.

Life cycle of Coccidioides spp. During the saprobic phase (left) the organism grows as mycelia, which mature into arthroconidia. These asexual conidia can be inhaled by a susceptible host. If this occurs, the fungus undergoes a morphological shift to form a spherule (right). The spherule structure matures to contain endospores, which can potentially disseminate to other body sites in the host including skin, bones, or central nervous system.