RV Pet Vet: Valley Fever, A Fungus Among Us

RV Pet Vet: Valley Fever, A Fungus Among Us

Ask the RV Vet

With Dr. Deanna Tolliver, M.S., DVM

If you travel to or live in the American Southwest, you need to be aware of a fungal disease that can affect you, your dog, or your cat.


Commonly called Valley Fever, after the Central Valley of California where it is endemic, the disease is also found in TX, AZ, NM, NV, UT, and south-central WA. The fungus lives dormant in soil during dry spells. After a rain, it rises up to ground level, changes to a spore, and then is spread by winds during the next dry spell. The offending organism is formally called Coccidiodes immitis.

*This is NOT a zoonotic disease: you can NOT become infected by your pet if it has Valley Fever, and your pet cannot become infected by another dog or cat.*

The disease has been reported in a wide variety of mammals, including alpacas, cattle, and horses.

Cats are infected much less often than dogs: about 1 cat per 50 dogs. This is probably because cats are less likely than dogs to dig in the soil. The treatment of both is the same, but the symptoms can be quite different.

In dogs, symptoms can include:
• a chronic cough, either dry or moist
• fever
• weight loss
• decreased appetite
• swollen lymph nodes
• lameness, if the disease spreads to the bones

In cats, the symptoms are:
• skin lesions, like an abscess (most common)
• fever
• loss of appetite
• weight loss

Diagnosing Valley Fever in pets, and humans can be a little tricky. Many cases are misdiagnosed in people every year because the symptoms can mimic other diseases. Veterinarians in the Southwest are familiar with the disease. But if you are a snowbird and your pet is infected with Valley Fever, AND you return home before your pet shows symptoms, your veterinarian in Minnesota or Iowa may have never seen a case.

In my own practice in the Midwest, I saw only two cases in 25 years. Both were dogs and both had spent the winter in Arizona with their snowbird parents. Luckily, the owners took their dogs to veterinarians in Arizona before returning home. Otherwise, Valley Fever may not have been high on my initial diagnosis list.

Diagnosis is based on geography, symptoms, and blood titer levels showing the presence of antibodies against the fungus. Finding the organism in a lesion or biopsy confirms the diagnosis.

Treating Valley Fever can be frustrating and expensive. Generally, medication needs to be given for six months or longer. The mainstay of treatment is antifungals, such as itraconazole or fluconazole. A cough suppressant may be given if coughing is severe. Supportive care such as rest and good nutrition are also important.

This disease is one of the most severe fungal infections our pets can contract. The prognosis for recovery is good if just the respiratory system is affected and treatment is given. If the fungus has become disseminated throughout the body, there is a guarded prognosis. Relapses are common.

Unfortunately, for both people and our pets, inhaling only 1-10 spores can cause the disease.

How do I prevent getting Valley Fever? 
“There is no prevention or vaccine at this time. Avoiding activities associated with dust and airborne dirt of native desert soil is recommended, but it is not a certain means of prevention, as the dust may or may not contain coccidioides spores. Some occupations recommend wearing masks. Use common sense and stay out of the blowing dust.” From: Valley Fever Center for Excellence (see link below).
The bottom line: if you winter or live in any of the states where Valley Fever is known to occur, be sure to take your dog or cat to a veterinarian if it shows any of the symptoms. Early treatment is critical to recovery. Snowbirds: If your pet shows any of these symptoms after you return home, be sure to tell your veterinarian where you and your pet have spent the winter.

Have you or your pet been diagnosed with Valley Fever? Or do you know someone or a pet that has? We want to hear from you!

The University of Arizona College of Medicine has a website dedicated solely to Valley Fever in people, dogs, and cats: Valley Fever Center for Excellence.

Dr. Deanna welcomes your questions. Email her at YourRVvet@gmail.com 

Dr. Deanna Tolliver has been a full-time RVer for a little more than 3 years, although she has been an RVer for several more. She pulls a fifth wheel with her 1-ton dually truck. Her travel companions include 4 small dogs (3 Chihuahuas: Tootie, Chiquita, and BooBoo, and a Yorkie, Janie), and a 36-year-old Yellow-Naped Amazon Parrot named Toby. She has a BS and MS in biology and zoology, respectively, and a Doctorate of Veterinary Medicine from the University of Missouri, Columbia. She owned a veterinary hospital for many years and recently handed over the reins to a new owner. Her hobbies include sewing, especially quilting, crafts, reading, and writing. 

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5 thoughts on “RV Pet Vet: Valley Fever, A Fungus Among Us

  1. Ginger M

    So glad you’re discussing this illness. My dog contracted it when we came to Arizona from Washington state and California in November and did not survive. I had no idea about it beforehand.
    My question:
    Do dogs born and raised here have any immunity, and what is the prevalence ?
    Thank you,

    1. Dr. Deanna

      Hi Ginger,
      I am so sorry to hear about your dog. Valley Fever is a very serious disease, the most devastating fungal disease in dogs.
      There are no statistics available regarding immunity in native AZ dogs. But the Valley Fever Center for Excellence at the University of Arizona currently has a study underway to further understand immunity in dogs. Many dogs are exposed to the fungal spores and some do not get sick or have a mild case. It’s these dogs that the Center wants to study, and they have put out a call for blood samples from dogs that have never been diagnosed with Valley Fever. Because some dogs don’t become ill even after exposure, the prevalence is unknown. The same group is working on a vaccine, first for dogs, then for people. Hopefully it will be available soon. Thank you for writing.

  2. Marty

    I got Valley Fever my first trip out in my RV. My dog was spared.

    I really think the people here Need to read about Valley Fever, maybe post it under a different title . Thanks

  3. Alice Hamilton

    About the soil disease,you say cat are less likely to dig in the soil. ( wrong!!!! ) sounds like your cat has never been outside,cats always dig in the soil to go potty,then cover it up,then if a dog discovers it they will roll around in it or if you have a house cat litter boxed trained,your dogs will go in and eat the poop..Gross Huh!

    1. Dr. Deanna

      Hi Alice. You’re right…sometimes dogs can do some pretty gross things! As far as cats digging in the soil, I’m thinking they don’t dig deep enough to disturb the spores of the fungus, but that would need to be verified. Also, when they do dig a “potty hole,” they generally don’t have their noses to the ground, like a dog would if it was digging a hole. Regardless of the reason, there are far fewer reported cases of Valley Fever in cats than in dogs. Thanks for writing!

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