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Az researchers turn to dogs to better understand Valley fever

PHOENIX – Some dogs cough. Others lose their appetite. And some dogs don’t show any symptoms at all.

Valley fever has become relatively common in dogs. A University of Arizona indicated that dogs raised from birth in Pima or Maricopa counties have a 6 percent probability of becoming sick with Valley fever by age 2.

The Translational Genomics Research Institute recently launched a new study to gather information on dogs and Valley fever. The Valley Fever Paws is collecting data on breeds of dogs diagnosed with Valley fever or exposed to the fungus – but not infected. TGen researchers hope the data will provide information not only on dogs, but how the disease affects people as well.

Valley fever is caused by a fungus found in the Arizona desert soil. When something disturbs the soil, the fungal spores blow into the air and enter the body through the lungs. A person or a canine can develop a lung disease, but most often the infection goes unnoticed.

Symptoms are usually a cough or fever, which makes it hard to detect. In dogs, it looks like a cold or flu.
Dr. Bridget Barker, an associate professor of TGen North’s center for fungal pathogens, said that most of the research on Valley fever has been on mice, but none of the insights really apply to humans. She said dogs are more closely related to humans and therefore make better models.

“The disease isn’t going to be exactly the same, but from work that has been done at TGen, as well as other places, we found that dogs actually have provided a lot of really good information about disease, the variation in disease, looking for specific host factors, looking for specific genes, specific immunology features,” Barker said. “It’s just a really great model system basically.”

Both dogs and humans have similar incidences of Valley fever. Five to 10 percent of the cases become severe for both populations.

Dr. Brett Cordes, a veterinarian at the Arizona Animal Hospital in Scottsdale, said he diagnoses at least one dog each week with Valley fever. Cordes is part of TGen’s national advisory council for their animal interests.

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“Any dog, any breed can get the disease, but it seems there are a few that are at higher risk,” he said. “I would say Labrador retrievers, golden retrievers, boxers are notorious for Valley fever.”

Cordes also said some dog breeds do not respond well to Valley fever even with medicine. It’s a similar situation with humans. Some ethnic groups, such as the Filipino and African American populations, seem to have more trouble with the disease, Barker said.

“It’s something we don’t understand,” Barker said. “We don’t understand why certain patient populations, certain ethnic groups, have more trouble with the disseminated forms of the disease.”

One problem is that the testing for Valley Fever is the same one that’s been used for several years, Cordes said. Tests can sometimes be a false negative or a false positive.

Cordes said that despite the prevalence in Arizona, there’s very little information on it.

Barker hopes the Valley Fever Paws project will help researchers discover the traits that make a host more susceptible to severe disease. The researchers want to have more than 2,000 participants, and TGen may ask some dog owners to provide a DNA sample using a cheek swab.

“There are very few people out there doing basic research on this organism,” Barker said. “And it’s that basic research that allows us to gain the knowledge about this rare organism that would then be translated into the clinic and greatly affect patients and improve patient outcomes.”

Pet owners can register their dogs for the project at TGen.

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Dr. Brett Cordes, a veterinarian at the Arizona Animal Hospital in Scottsdale, said he diagnoses at least one dog each week with Valley fever.

Facts about Valley fever

  • There is no vaccine or cure.
  • Each year, nearly 150,000 Americans are infected and as many as 500 die annually.
  • Dogs have cold- or flu-like symptoms, starting about five to 21 days after exposure.
  • Nearly 30 percent of dogs in Tucson catch Valley fever by the age of 2.
  • 6 percent of these dogs will show clinical signs of illness.

Source: Translational Genomics Research Institute