New research indicates that certain agricultural practices and natural landscapes influence the incidence of Valley Fever infections across the state.
RT’s Three Key Takeaways:
- Landscape Risk Factors: Naturally dry landscapes and specific crops like grain and hay are associated with higher rates of Valley fever, while orchards and rice fields are linked to lower incidence.
- Agricultural Fallowing Impact: Newly fallowed farmland may increase the risk of fungal spore exposure, suggesting that land management decisions have significant public healthcare consequences.
- Protective Recommendations: The study supports the use of dust-control measures and respiratory protection, such as N95 masks, for outdoor workers during high-risk seasons.
Certain landscapes surrounding California communities are associated with differing rates of Valley fever, according to a study published in Science Advances.
Valley fever, or coccidioidomycosis, is a fungal respiratory infection caused by inhaling Coccidioides spores carried in windblown dust. In California, rates of the disease have increased by more than 800% over the past two decades. While many people do not develop symptoms, those who do can experience debilitating illness lasting months, with some infections spreading beyond the lungs or causing long-term lung disease.
“California is undergoing a major transformation of its agricultural landscape, and we need to understand how those changes may affect public health,” said Alexandra Heaney, PhD, assistant professor at the Herbert Wertheim School of Public Healthcare and Human Longevity Science at UC San Diego. “Our findings suggest that land management decisions can have consequences that extend beyond agriculture and water use.”
To investigate the link between land use and disease, researchers from UC San Diego and UC Berkeley analyzed 65,657 confirmed Valley fever cases reported to the California Department of Public Healthcare between April 2008 and March 2021. These cases were linked to high-resolution maps showing natural vegetation, crop types, and fallowed fields across 20 California counties.
The researchers found that communities surrounded by greater amounts of shrubland, barren land, and grassland had higher rates of Valley fever. Specific agricultural land uses, including grain and hay fields, sorghum, soybeans, corn, and cotton, were also associated with higher incidence. Conversely, greater areas of orchards, fruits, vegetables, and rice were associated with lower incidence.
Fallowing—the practice of leaving land unseeded—also emerged as a factor. While total fallow land was not significantly linked to incidence, larger areas of newly fallowed land were associated with higher disease rates. This relationship varied based on the land’s previous history, with newly fallowed land previously used for mixed crops showing the highest association with disease.
The findings have potential implications as the Sustainable Groundwater Management Act accelerates the fallowing of agricultural land in the San Joaquin Valley. The authors suggested that their findings support the use of dust-control measures on retired fields and enhanced surveillance for outdoor workers. Protective measures could include air quality warnings and respiratory protection such as N95 masks.
“As California adapts to water scarcity and changes in agricultural production, we must weigh the public healthcare consequences of those transitions alongside their environmental and economic impacts,” said Justin Remais, PhD, professor at the UC Berkeley School of Public Healthcare. “If we can determine how decisions like fallowing land may contribute to the release of Coccidioides spores, we can design strategies to inform and protect communities from exposure.”
