Tejal Somvanshi
Does your dog love to dig? That enthusiastic paw-scratching might be providing scientists with crucial health data. New research shows our canine companions could serve as early warning systems for a potentially serious fungal disease that’s expanding its reach across the American West.
Dogs as Disease Detectives: The UC Davis Study
A groundbreaking study from the University of California, Davis has revealed that dogs can act as sentinels for Valley fever, a fungal infection that’s becoming more widespread as climate patterns shift.
“Dogs are sentinels for human infections,” explains lead author Jane Sykes, 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.”
Published in the Journal of Infectious Diseases, this comprehensive research examined nearly 835,000 blood antibody tests from dogs across the United States between 2012 and 2022. The results? Almost 40% tested positive for Valley fever.
What Exactly Is Valley Fever?
Valley fever, scientifically known as coccidioidomycosis, is caused by a fungus that thrives in moist soils and becomes airborne during drought conditions. When we inhale these microscopic spores, infection can occur.
The disease has traditionally been associated with the southwestern United States, but its footprint appears to be expanding—and climate change may be partly responsible.
“Climate change is creating the perfect conditions for it in the Western United States, with increasing heavy rains followed by prolonged drought,” the UC Davis researchers note. These weather patterns create ideal conditions for the fungus to grow during wet periods and then disperse during dry spells.
A Disease on the Move
Perhaps most striking is how quickly Valley fever is spreading in the canine population. Sykes and her colleagues mapped positive test results geographically and found that Valley fever in dogs expanded from just 2.4% of U.S. counties in 2012 to 12.4% by 2022—a five-fold increase in just a decade.
“We were also finding cases in states where Valley fever is not considered endemic,” Sykes emphasizes. “We should be closely watching those states because there could be under-recognition of the emerging fungal disease in humans.”
The Centers for Disease Control and Prevention (CDC) considers Valley fever endemic in parts of six states: Arizona, California, Nevada, New Mexico, Texas, and Utah. However, the UC Davis study found cases in dogs from several additional states, including Oregon, Washington, Idaho, Montana, Wyoming, and Colorado.
Similar Posts
By the Numbers: Where Valley Fever Is Hitting Hardest
The geographical distribution of positive tests tells an important story:
- Arizona: 91.5% of all positive tests
- California: 3.7%
- Nevada, Utah, Colorado, New Mexico, and Texas combined: 2.6%
- Washington, Oregon, and Idaho combined: 0.6%
- All other states combined: 1.3%
Arizona also had the highest incidence rate—approximately 100 times higher than rates in California, Nevada, and New Mexico.
Why Dogs Are Particularly Vulnerable (And Valuable)
Dogs that enjoy digging—which includes most medium-to-large breeds and especially terriers—face higher risk of exposure. Their close contact with soil increases the likelihood of inhaling fungal spores.
And since dogs typically travel less than humans do, finding Valley fever in dogs strongly suggests the fungus is present in the local environment. Sykes emphasizes that “the sheer number of cases cannot be explained by dogs visiting other states, since dogs travel far less frequently than humans.”
Importantly, the study found that dog cases correlated with human cases in known Valley fever “hot spots” like Arizona, California, Texas, New Mexico, and Nevada.
The Human Impact: A Hidden Epidemic?
The CDC receives 10,000 to 20,000 reports of human Valley fever cases annually. However, researchers believe the actual number may be at least 33 times higher due to underreporting and misdiagnosis. Many states don’t require reporting of human cases, making it difficult to track the disease’s true prevalence.
What Valley Fever Looks Like in Dogs and Humans
Dogs with Valley fever often show similar symptoms to humans:
- Coughing as the infection develops in the lungs
- In more severe cases, the fungus can spread to bones, brain, and skin
- Advanced infections may require lifelong antifungal treatments
- The disease can be fatal in both dogs and humans
From Pet Health to Public Health
Sykes suggests that dogs are “an under-recognized model for understanding Valley fever.” By studying the disease in our four-legged friends, scientists may develop new diagnostic tests and treatments that benefit humans as well.
“By learning more about Valley fever in dogs, scientists may discover new tests or treatments for the disease in humans. They may also help prevent misdiagnosis or undiagnosed disease in humans,” the researchers note.
The study was a collaborative effort between UC Davis and UC Berkeley, with additional authors including George Thompson III of UC Davis School of Medicine and Simon Camponuri, Amanda Weaver, and Justin Remais of UC Berkeley’s School of Public Health. Funding for the Berkeley portion of the research came from the National Institute of Allergy and Infectious Diseases of the National Institutes of Health.
Staying Safe: What Dog Owners Should Know
If you live in or are traveling to regions where Valley fever is present—especially if you have a dog that loves to dig—be aware of the potential risks. While no specific preventive measures were outlined in the study, understanding the symptoms and seeking prompt veterinary care could make a significant difference in outcomes for both you and your furry companion.
As climate patterns continue to shift and Valley fever expands into new territories, your dog’s health could provide valuable early warnings about environmental risks that affect human health too. Sometimes, it seems, our best friends might also be our best health monitors.
Frequently Asked Questions
Valley fever (coccidioidomycosis) is a fungal infection caused by inhaling spores from soil. In dogs, it typically starts as a respiratory infection with symptoms like coughing, but can spread to bones, skin, and other organs in severe cases. Dogs are particularly vulnerable because their digging behavior can expose them to more fungal spores. The disease can be serious and sometimes requires lifelong treatment in both dogs and humans.
Valley fever has traditionally been associated with the southwestern United States, particularly in Arizona, California, Nevada, New Mexico, Texas, and Utah. However, recent research suggests the geographic range of the disease is expanding, with cases now being identified in Oregon, Washington, Idaho, Montana, Wyoming, and Colorado. Arizona has the highest concentration of cases by far.
No, Valley fever cannot be transmitted directly from dogs to humans or between animals. Both humans and dogs contract the disease by inhaling fungal spores from the environment. However, the presence of Valley fever in dogs can serve as an early warning system for the disease’s presence in a particular area, potentially alerting humans to their own risk of exposure.
Common symptoms of Valley fever in dogs include coughing, fever, weight loss, lack of appetite, and lethargy. In more severe cases where the infection spreads beyond the lungs, dogs may develop lameness, bone lesions, swollen lymph nodes, or neurological problems. Symptoms can vary widely in severity, from mild respiratory issues to life-threatening systemic disease.
Climate change is creating ideal conditions for the spread of Valley fever. The fungus that causes the disease thrives in soil during wet periods but becomes airborne during drought conditions. Increasing patterns of heavy rainfall followed by extended drought in the Western United States have created perfect conditions for the fungus to grow and then disperse. This changing climate pattern is believed to be contributing to the five-fold increase in affected counties over the past decade.
While it’s difficult to completely prevent exposure in endemic areas, you can reduce risk by limiting your dog’s digging activities, especially during dry and windy conditions when spores are more likely to be airborne. Be aware of symptoms and seek prompt veterinary care if you suspect your dog might be infected. If you’re traveling with your dog to known Valley fever regions like Arizona, be particularly vigilant. There is currently no vaccine available for Valley fever in dogs or humans.
