A Cure for Our Dust: Animal Testing Leads to New Developments in Treatments for Valley Fever

Tanner was missing. My whole family was shaking with fear as we called into the late afternoon rain for him to come back inside. I raced across my backyard looking for any sign of him. I trekked through the mud to a scarcely visited comer of my yard, looking for any place he might have been hiding. The sight I found was heartbreaking. There, unmoving against the wall behind the bushes and coated in muddy water, was Tanner, my usually loving, playful, and friendly golden retriever. I rushed to coax him into the house and quickly discovered that Tanner would only walk on three legs. Inside, he collapsed next to the water dish while crying out. He eventually calmed down but still refused to move. After several visits to the veterinarian and a blood test, Tanner was finally diagnosed: he had valley fever.

Valley fever, or Coccidioidomycosis, is a fungal disease found in the desert in Arizona, California, Nevada, New Mexico, Texas, Utah, and northern Mexico. Eighty percent of cases, however, are reported in Arizona, and a majority are found in the Phoenix-Tucson corridor. Some believe that as many as thirty thousand humans and sixty thousand dogs contract valley fever each year, but many of these cases go undiagnosed. Valley fever is not contagious, but it can be contracted by simply breathing dust containing fungal spores. Once infected, there are two different forms valley fever can take: the primary disease, where the fungus stays localized in the lungs, or the disseminated disease, where the fungus spreads to other parts of the body. Tanner was diagnosed with the latter as the disease had spread to his bones and joints and presented as fatigue and a leg injury.

While there is no cure for valley fever, anti-fungal medications are available to treat it. The veterinarian prescribed Tanner with fluconazole, which was originally tested on mice by infecting them with a lethal fungus and then administering the anti-fungal. The study showed that of the mice who were administered fluconazole, ninety percent were still alive after ninety days. Additionally, various side effects of the anti-fungal were recorded and it was found that the most severe side effect was in the deterioration of the kidneys. Because of the animal testing, fluconazole was able to be safely administered to people and larger animals to treat valley fever. With fluconazole, Tanner's symptoms are no longer severe. Also, because possible kidney deterioration was identified during the mice trials, Tanner's veterinarian prescribed a supplement to protect Tanner's kidneys.

Unfortunately, because fluconazole is not a cure, Tanner exhibits occasional symptoms and continues to need medication twice daily. Fortunately, a cure or even a vaccine may soon be available thanks to new research at the University of Arizona. The most promising cure currently being researched is nikkomycin Z (NikZ). NikZ is based on a bacteria that blocks an enzyme necessary for fungal growth. Initial studies on mice found that large enough doses of NikZ saved one hundred percent of mice injected with a lethal amount of valley fever fungus. More recent studies aim to identify an optimal dosage by comparing the effect of different doses of the drug on infected mice with the results of a clinical trial on humans.

In addition to seeking a cure for valley fever, researchers also are working to develop a vaccine, Delta-cpsl, to prevent infections by removing a gene from the valley fever fungus. Delta-cps 1 was tested on mice with remarkable results:  the vaccinated mice survived even after being exposed to one hundred times a lethal dose of valley fever while nearly all of the unvaccinated mice died from the fungus. These results suggest that a viable vaccine could soon be produced to prevent valley fever in both dogs and humans.

Although the recent studies of NikZ and Delta-cpsl have not yet resulted in a commercially-available product, they have brought new hope that valley fever will soon be eradicated or at least easily treatable. Today, I am particularly thankful that past studies have resulted in the development of fluconazole, a treatment for Tanner that allows him to be comfortable and happy. With the help of animal studies on new treatments, cures, and vaccines, I have an abundance of hope that Tanner and his canine friends soon will be free to endlessly roll and dig in the Arizona dirt without worrying about the fungus that lurks in its dust.