What to Know About Valley Fever in Dogs

Medically Reviewed by Vanesa Farmer, DVM on January 04, 2022
4 min read

If you live in the southwestern U.S., you have probably heard of valley fever. This respiratory infection affects thousands of people per year. The fungus that causes valley fever in humans can also affect dogs. Most dogs recover from this infection, but there are some cases in which dogs become extremely sick. Without treatment, some dogs die. 

Valley fever is a respiratory infection that dogs get from inhaling mold spores in the dirt. The disease is also known as California disease, desert rheumatism, and San Joaquin Valley fever. The fungus that causes the disease is typically found in the southwestern U.S., northwestern Mexico, and Central and South America. It has also been found in Washington state.

Humans and other animals are susceptible to valley fever, but it is not contagious. The only way to get infected is by directly breathing in the mold spores that cause the disease. Pets can’t pass it to other animals, and humans cannot pass it to other people.

Valley fever is a fungal infection caused by breathing in the spores of organisms called coccidioides. The fungus lives in soil and produces long filaments that contain infectious spores. When the soil is disturbed, the spores become airborne. Animals and people breathe them in without realizing it.

Dogs are prone to inhaling coccidioides spores. Their natural inclination to sniff means they often have their noses in contact with the soil. If they dig in the dirt, they may be releasing spores and then inhaling them.

Once the spores enter your dog’s lungs, they develop into structures called spherules. In healthy dogs, the immune system can isolate the spherules and prevent them from spreading or causing symptoms. In young puppies, older dogs, and dogs with underlying health issues, though, the spherules can grow and spread in the lungs, which can cause significant respiratory problems.

In some cases, the spherules spread from the lungs to other parts of the body. When this happens, your dog can become very ill. The disease can affect their joints, eyes, or nervous system.

There are two forms of valley fever in dogs. The primary form is limited to the lungs. If the infection spreads to other areas of your dog’s body, it’s the disseminated form. 

Symptoms of primary valley fever usually include: 

  • Coughing
  • Fever
  • Low appetite
  • Lack of energy
  • Weight loss

Symptoms of the disseminated disease often include the symptoms of the primary disease, along with: 

  • Back or neck pain
  • Enlarged lymph nodes under the chin, in front of the shoulder blades, or behind the stifles
  • Eye inflammation
  • Lameness or swelling in the legs and paws
  • Seizures
  • Swelling under the skin
  • Skin wounds that don’t heal
  • Swollen testicles

Your vet will prescribe antifungal medicines such as fluconazole, itraconazole, and ketoconazole to treat valley fever. They are effective at reducing symptoms and clearing the fungal infection from your dog’s system.

Treatment for primary valley fever is usually a long-term course of antifungal medicine. Your dog will need to take medicine for six to 12 months. While your dog is taking the medication, they will need to visit the vet regularly. The vet will do bloodwork to make sure your dog doesn’t develop side effects on organs such as the liver. Symptoms usually improve within a few weeks after your dog starts the treatment. 

If the disease has spread outside of the lungs, your dog may need to stay on the medication longer to clear the infection. If the fungus has gotten into their nervous system, your dog might need medication for the rest of their life. 

If your dog is very ill and isn’t eating or drinking, your vet may suggest hospitalizing your pet for a short period of time. Medical staff can give your dog intravenous fluids and nutrition to help them recover. Your vet may also offer medicine to treat symptoms like coughing or a fever and make your pet more comfortable. 

In rare cases, the disease progresses too far for treatment to be effective. Talk to your vet about your options. You may want to consider palliative care or humane euthanasia in certain cases.

Preventing exposure to valley fever spores is the best way to protect your dog. If you live in a region where valley fever is a risk, you should keep your dog indoors more than outdoors. Prevent your dog from digging when they are outside, and try to stay away from areas where the soil is loose and dusty, such as construction sites or spaces with limited ground-cover plants.

There is a vaccine for valley fever that is in development. It had good initial results in clinical trials and may be available within the next few years.