LB 9-86 - Valley fever spreads beyond endemic regions

Background/Question/Methods:

Valley fever is a fungal infection that is caused by two species in the genus Coccidioides. Infection occurs when mammals inhale airborne spores that are discharged from soil. Valley fever is known to be endemic to the Southwestern United States, but in the past decade, the range of Valley fever has been suspected to have increased. Climate change has been implicated in this range expansion from hyper-endemic regions such as Southern Arizona to Northern Arizona. Climate fluctuations associated with the spread of Valley fever are higher temperatures, precipitation shifts, and drier soils. Due to this reemergence, there is an urgent need to understand the ecological niche and determine the extent of the spread of Coccidioides spp. in the Southwestern United States. Our objective is to determine the extent of the spread of Valley fever due to climate fluctuations. We took eight years of environmental surveillance data from various sites throughout Arizona, and performed DNA extractions on the soil samples. Using the data from RT-qPCR analysis on the samples, with climate data such as annual mean precipitation and annual mean temperature from WorldClim, we created an ecological niche model to predict the current and future range of Coccidioides spp.

Results/Conclusions:

The current prediction of the ecological niche model showed an increase in range of Valley fever in Arizona, spreading from hyper-endemic areas like Southern Arizona to previous non-endemic regions of the Western United States, such as Utah, New Mexico, and parts of Northern California. Following these continuing climate trends of higher temperatures and precipitation shifts, the ecological niche model predicted Valley fever to spread all across the Western United States. The knowledge gained from soil sampling and ecological niche modeling will lay the foundation to better understand disease surveillance, as well as how global climate change will exacerbate this and other environmentally-acquired pathogens in the coming decades.