Dogs could help predict spread of Valley fever in humans: Study

The Hill

10-04-2025

California scientists have determined that dogs might be able to help predict the spread of a dangerous fungus, which has surged in recent years due to the impacts of climate change.
Drought conditions across the Golden State have been ramping up the dispersal of a soil-dwelling organism called coccidioides, which causes the flu-like disease known as coccidioidomycosis, or 'Valley fever.'
The disease, which can cause grave or even deadly complications, has risen sharply among California residents over the past two decades: Reported cases tripled from 2014 to 2018 and again from 2018 to 2022.
Valley fever was previously concentrated in parts of Arizona and California's lower San Joaquin Valley. Rather than passing from person to person, the disease develops from the direct inhalation of these fungal spores.
But Valley fever is also common in animals, particularly dogs that dig in the dirt, according to researchers from the University of California, who published a study on Thursday in the Journal of Infectious Diseases.
The scientists assessed nearly 835,000 blood antibody tests taken from dogs nationwide between 2012 and 2022 — and found that 40 percent tested positive for the disease.
'Dogs are sentinels for human infections,' lead author Jane Sykes, a professor of small animal internal medicine at the UC Davis School of Veterinary Medicine, said in a statement.
'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,' she added.
Along with colleagues at UC Berkeley, Sykes mapped positive results by location and found that the presence of Valley fever in dogs surged from just 2.4 percent of U.S. counties in 2012 to 12.4 percent in 2022.
'We were also finding cases in states where valley fever is not considered endemic,' Sykes said. 'We should be closely watching those states because there could be under-recognition of the emerging fungal disease in humans.'
The sheer number of cases, the authors explained, cannot be attributed to dogs visiting other states, since the animals travel far less frequently than humans do. Dog cases were also correlated with human Valley fever 'hot spots,' per the study.
Arizona was responsible for 91.5 percent of positive tests, followed by California at 3.7 percent; Nevada, Utah, Colorado, New Mexico and Texas at 2.6 percent combined; and Washington, Oregon and Idaho at 0.6 percent combined.
The remaining states reported far fewer positive results, with 1.3 percent combined, the researchers found.
The authors also determined that dog breeds that tend to dig, such as medium-to-large animals and terriers, are more likely to get Valley fever. They also exhibit some of the same symptoms of the disease that humans experience, including a cough and lung infection.
The fungus can spread to the bones, brain and skin and require lifelong anti-fungal injections, and can potentially result in death, the scientists warned.
By learning more about Valley fever in dogs, Sykes suggested that humans could develop new tests or routes for treatment — potentially preventing misdiagnosis or undiagnosed disease among themselves.