Valley Fever: Environmental Risk Factors and Exposure Pathways Deduced from Field Measurements in California

Area of Science:

• Environmental microbiology
• Mycology
• Public health

Background:

• Coccidioidomycosis, or Valley fever, is endemic in southwestern US arid regions.
• Military personnel stationed in these areas have historically been at risk.
• Understanding pathogen prevalence in soil is crucial for risk assessment.

Purpose of the Study:

• To determine the prevalence of Coccidioides in soil and dust samples near California military bases.
• To identify environmental factors associated with Coccidioides presence.
• To assess the risk of Coccidioides exposure for military personnel and the public.

Main Methods:

• DNA extraction and Polymerase Chain Reaction (PCR) were used to detect Coccidioides.
• Soil and dust samples were collected from diverse locations near three military bases.
• Physical and chemical parameters of sampling sites were analyzed.

Main Results:

• Coccidioides DNA was detected in soil and dust samples, confirming its presence.
• The Mojave Desert (near Twentynine Palms MCAGCC) had the highest prevalence of positive samples.
• San Joaquin Valley sites (near NAS Lemoore) showed lower prevalence, mainly in semi-natural areas.
• No significant differences in physical/chemical parameters were found between positive and negative sites.

Conclusions:

• Soil disturbance around military bases increases Coccidioides exposure risk.
• Undisturbed native vegetation sites (Creosote, Salt Bush) pose a higher risk, particularly during dry periods.
• Severely disturbed lands are less suitable for Coccidioides growth, reducing risk.