COCCIDIOIDES POSADASII HOT SPOTS: CHARACTERIZATION OF VALLEY FEVER-RIDDEN ARIZONA SOILS

Coccidioidomycosis, or “Valley Fever,” is a disease caused by inhalation of the soil-borne fungal arthroconidia (spores) of Coccidioides spp. More than 20,000 cases of Coccidioidomycosis were reported to the CDC in 2019, with most of the cases occurring in residents of highly endemic areas (California’s San Joaquin Valley [C. immitis] and Arizona’s Sonoran Desert [C. posadasii]). Coccidioides is not evenly distributed throughout these endemic areas, instead it is found in “hotspots”. Factors controlling the geographic range and distribution of Coccidioides are not well defined, although soil, climatic, and environmental properties are expected to be important. Additionally, the ecological niche of Coccidioides is still poorly understood, and it remains uncertain whether these fungi are mainly linked to small mammals, such as burrowing rodents, or if they exist as saprotrophs in soil. This study aims to better understand the habitat of C. posadasii by determining correlations between its presence or absence and soil physicochemical properties. Soils were collected from both burrows and non-burrows at 3 known C. posadasii positive locations in Arizona, across Maricopa, Pima, and Pinal counties. Soil chemistry was evaluated on soil extracts, including pH, electrical conductivity (EC), dissolved organic matter content, and soluble and exchangeable ion compositions. Particle size distribution (PSD) was determined to establish soil texture and aid in the prediction of porosity and reactivity. Physical properties including soil temperature and water content are continuously measured in-situ at the sites. Work is ongoing to determine soil characteristics and conditions that are essential to fungal growth and to constrain C. posadasii habitat. The larger objective of this research is to aid in the development of a predictive geospatial model of C. posadasii incidence in the state of Arizona.