Valley fever, or coccidioidomycosis, is a fungal disease caused by Coccidioides spp., which thrives in moist soils and becomes airborne during drought conditions. Inhalation of these spores can lead to serious respiratory illness in both humans and animals.
Climate change, characterized by increased heavy rains followed by prolonged droughts, is creating ideal conditions for the fungus to proliferate in the Western United States.
Dogs as Sentinels for Human Infections
A new study from researchers at the University of California, Davis, in collaboration with UC Berkeley, finds that dogs can serve as effective sentinels for tracking the spread of Valley fever in humans.
Analyzing nearly 835,000 canine blood antibody tests collected between 2012 and 2022, the researchers found that approximately 40% of dogs tested positive for Valley fever antibodies. This strong correlation between dog and human cases was most evident in states like Arizona and California. The disease generally effects dogs that like to dig, including medium to large dogs as well as terriers.
“Dogs are sentinels for human infections,” said Dr. Jane Sykes, lead author of the study and professor of small animal internal medicine at the UC Davis School of Veterinary Medicine. “They can help us understand not just the epidemiology of the disease but they’re also models to help us understand the disease in people.”
Geographic Expansion of the Disease
The study’s geographic analysis showed that Valley fever in dogs expanded from affecting 2.4% of U.S. counties in 2012 to 12.4% in 2022. Notably, cases were identified in states not traditionally considered endemic for Valley fever, including Oregon, Washington, Idaho, Montana, Wyoming, and Colorado.
Arizona reported the highest rate of Valley fever in the study, accounting for 91.5% of positive canine tests, according to Science Daily.
This expansion indicates a potential under-recognition of the disease in humans within these emerging regions.
Implications for Public Health Surveillance
The strong correlation between canine and human cases underscores the potential of using dogs as early indicators for human Valley fever outbreaks.
Since dogs often have limited travel ranges and are more likely to dig in soil where the fungus resides, their infections can reflect local environmental conditions. Monitoring canine cases could, therefore, enhance public health surveillance and lead to earlier detection and intervention in human populations.
Call for Enhanced Reporting and Research
Currently, there is no mandatory reporting system for canine Valley fever cases, which limits the ability to monitor and respond to the disease’s spread effectively.
By tracking Valley fever in dogs, it can alert health professionals to the possible presence in human patients. It could also help scientists develop better diagnostic tools and treatments that also benefit human medicine.
A One Health Approach for a Worsening Threat
As climate change continues to alter ecosystems, the spread of Valley fever is likely to accelerate. Monitoring dogs as sentinel species offers a promising way to detect outbreaks earlier and reduce the risk to humans.
Public health officials, veterinarians, and researchers emphasize the need for stronger surveillance systems, cross-disciplinary collaboration, and expanded reporting to mitigate the growing threat posed by Valley fever.
