Coccidioides Niches and Habitat Parameters in the Southwestern United States

Abstract

To determine habitat attributes and processes suitable for the growth of Coccidioides, soils were collected from sites in Arizona, California, and Utah where Coccidioides is known to have been present. Humans or animals or both have been infected by Coccidioides at all of the sites. Soil variables considered in the upper 20 cm of the soil profile included pH, electrical conductivity, salinity, selected anions, texture, mineralogy, vegetation types and density, and the overall geomorphologic and ecological settings. Thermometers were buried to determine the temperature range in the upper part of the soil where Coccidioides is often found. With the exception of temperature regimes and soil textures, it is striking that none of the other variables or group of variables that might be definitive are indicative of the presence of Coccidioides. Vegetation ranges from sparse to relatively thick cover in lower Sonoran deserts, Chaparral-upper Sonoran brush and grasslands, and Mediterranean savannas and forested foothills. No particular grass, shrub, or forb is definitive. Material classified as very fine sand and silt is abundant in all of the Coccidioides-bearing soils and may be their most common shared feature. Clays are not abundant (less than 10%). All of the examined soil locations are noteworthy as generally 50% of the individuals who were exposed to the dust or were excavating dirt at the sites were infected. Coccidioides has persisted in the soil at a site in Dinosaur National Monument, Utah for 37 years and at a Tucson, Arizona site for 41 years.

Recent Advances in Our Understanding of the Environmental, Epidemiological, Immunological, and Clinical Dimensions of Coccidioidomycosis

“…The fungus has been found sporadically as far north as the Dinosaur National Monument in Utah, which suggests that it is possible that a suitable habitat exists in the Great Basin Desert (70). Also, spherules were identified histologically in the jaw of a bison, excavated in Nebraska, which was thought to have died about 8,500 years ago (71).…”

Comparative genomic analyses of the human fungal pathogens Coccidioides and their relatives

“…When not infecting a mammal, the fungus lives in the arid, alkaline New World deserts, where it is believed to grow as a filamentous soil saprophyte (Papagiannis 1967;Fisher et al 2007). The filaments produce asexual spores (arthroconidia), which are inhaled to initiate infection.…”

The past, present, and future of soils and human health studies

“…This topic includes heavy metals (e.g., Kibble and Saunders, 2001;Filippelli and Laidlaw, 2010;Taylor et al, 2010;Weindorf et al, 2013;Burt et al, 2014), radioactive materials (e.g., Yamada, 2003;Appleton, 2007;Hu et al, 2010), and organic chemicals (e.g., Albihn, 2001;Horrigan et al, 2002;Lee et al, 2003;Chamignon et al, 2008). Soil pathogens have also continued to receive attention (e.g., Jovic et al, 2001;Jenkins et al, 2002;Ross and Donnison, 2006;Fisher et al, 2007;. Additional benefits of soil organisms have been revealed; it is now thought that exposure to soil microorganisms is important in the prevention of allergies and other immunity-related disorders (Kay, 2000;Matricardi and Bonini, 2000;Haahtela et al, 2008;Rook, 2010).…”