Valley Fever (Coccidioidomycosis) in Dogs

Valley Fever Dog
X-Ray of Dog with Valley Fever Courtesy of Judy Hedding

Valley fever (coccidioidomycosis) is a respiratory disease in dogs (humans, too) caused by a fungus. It primarily occurs in Arizona and the desert Southwest since this fungus lives in the soil in those regions. It can affect all dog breeds, even those that visit for a short time since they all tend to sniff the ground and can breathe in the fungus spores. If left untreated, it can lead to a bad cough, seizures, lameness, and even death. Take a look at the symptoms, treatments, and ways that you can prevent your dog from getting the disease.

What Is Valley Fever?

Valley fever is a relatively common respiratory disease in dogs in the desert regions of Arizona, New Mexico, Nevada, Texas, California, and Utah. When a dog disturbs soil containing coccidioides spores by walking or digging, then sniffs the soil, the inhaled fungal spores enter the lungs.

About 70 percent of dogs exposed to the fungus can shrug it off, have an asymptomatic version of the disease, and develop an immunity to the fungus. The remaining population will show symptoms.

Symptoms usually occur within three weeks after infection, although sometimes, the organism can lay dormant in the body for up to three years before causing an infection. It can also disseminate or spread to other parts of the dog's body and develop into more problematic symptoms.

Signs of Valley Fever in Dogs

  • Coughing
  • Fever
  • Weight loss
  • Lack of appetite
  • Lack of energy
  • Lameness or swelling of the limbs
  • Back or neck pain with or without weakness or paralysis
  • Seizures
  • Soft, swollen abscesses under the skin
  • Non-healing, oozing wounds
  • Eye inflammation with cloudiness
  • Swollen testicles
  • Death


One of the most common symptoms in dogs with valley fever is a harsh, dry, hacking, or honking cough. It can sometimes be confused for kennel cough.


A dog that has a temperature of 103 F or higher has a fever. A dog's normal range is 99.5 to 102.5 F. A fever indicates that the dog is fighting off an infection—fungal, viral, bacterial, or parasitic. Visible signs of illness include red eyes, shivering, warm ears, and a warm, dry nose.

Weight Loss/Lack of Appetite

Refusing to eat more than two meals is uncommon for most dogs. Usually, when a dog is fighting off an infection or disease, dogs will develop a fever and lose their appetite. If a dog goes a few days without food, they will lose some weight.

Lack of Energy

Much like humans, when a dog is feeling sick, feverish, and not eating, a dog will lose its spunk, mope, seem tired, and even get depressed. Lethargy can be a clear sign that the dog's body is fighting off an infection.


If the disease spreads, the bones and joints are most commonly infected. Lameness is the most common sign that valley fever has spread past the respiratory system. The joints may become swollen and painful.

Back or Neck Pain and Seizures

The disseminated form of the disease can also spread to the central nervous system. If the fungus sets in there, it can affect the spinal cord and neurological processes of the brain. The infection at that site can lead to back and neck pain, paralysis, and seizures.

Skin Issues

Dogs can get soft abscess-like swelling under the skin or swollen lymph nodes under the chin, in front of the shoulder blades, or behind the stifles (dog's knees). They can develop non-healing, red lesions or skin wounds that ooze yellow or reddish fluid, especially after a bout of dermatitis or chronic scratching. 

Eye Inflammation

Valley fever can cause inflammation inside of the eye leading to retinal detachment and glaucoma (elevated pressure inside the eye that causes discomfort and vision loss). These diseases may appear like cloudiness of the eyes. Valley fever can also affect the eyelids and cause swelling or redness (more often in cats than dogs).

Swollen Testicles

A visible sign that the fungal infection is in the reproductive system is if the dog gets inflammation of the testes (called orchitis) in male dogs, which is when one or both testicles become hard and swollen.


A small number of dogs, usually those that develop disseminated or the spreading form of the disease, can die from valley fever.

Causes of Valley Fever

Two species of fungus spores can cause valley fever once inhaled in the dogs' lungs:

  • Coccidiodes immitis
  • Coccidiodes posadasil

Once inhaled, these microscopic spores create structures called spherules full of endospores, which are spores that reproduce. Large spherules release these multiplying endospores, which intensifies the infection and spreads it throughout the body.


Most veterinarians in desert regions are familiar with valley fever and know to look for it. However, if you are visiting a desert locale and return home with a sick dog, mention that your dog visited the sandy desert region with you.

Veterinarians have several ways to confirm whether a dog has valley fever. Tests include a valley fever blood test (also called cocci test, cocci serology, or cocci titer), general blood tests and blood cell counts, chest x-rays, and bone and joint x-rays. If your dog is experiencing paralysis, the doctor might order a CT or MRI scan of the brain or spinal cord.

A vet might also suggest a culture of fluid or tissue samples, or a biopsy or aspiration of cell, fluid, or tissue samples. Also, it is not uncommon to repeat a valley fever blood test in three weeks since it might take time for it to show up in tests.

Your vet may recommend any combination of these tests to check if this infection has spread to other parts of your pet's body.


Like most illnesses in dogs, early diagnosis will likely yield faster, more effective relief. Typically, the dog will get an anti-fungal medication, such as fluconazole, which is one of the gentlest antifungal medications on the liver.

Other antifungal drugs are available, and your veterinarian will discuss the pros and cons of each. Your dog may be on this medication for a year or longer and may require future tests for the disease. Relapses are possible.

To make your dog comfortable, your vet might prescribe a cough suppressant, an anti-inflammatory, or pain reliever.

A dog can die from valley fever, but if you continue regular checkups and quickly address your dog's health problems, it is usually treatable. If you reside in the desert region, a veterinarian may first try a regular antibiotic regimen to see if that resolves the cough. If that doesn't work, then valley fever tests might be ordered.

Can It Spread to Humans?

Valley fever is not transmitted between dogs, other animals, or to humans since an infection only occurs if you directly breathe the fungus into your respiratory system. However, humans can easily get exposed to the fungus at construction sites, a dust storm, or events that kick up a lot of dust.

How to Prevent Valley Fever

It is challenging to avoid valley fever altogether since it's on the ground and can be circulated into the air. You can, however, reduce your dog's likelihood of getting it or at least mitigate its impact.

  • Don't leave your dog in a non-landscaped yard or dog park. A grassy or rock/gravel landscape is safer.
  • Avoid walking or running with your dog in open desert areas or undeveloped dusty lots.
  • Do not leave your dog outside during dust storms or haboobs—a type of desert windstorm.
  • Pay attention to your dog's health warning signals; get your dog examined by a veterinarian if you notice any symptoms.
Article Sources
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  1. How Dogs Get Valley Fever | Valley Fever Center For ExcellenceUniversity of Arizona Health Sciences

  2. Symptoms - Valley Fever Center For ExcellenceUniversity of Arizona Health Sciences

  3. FAQs - Valley Fever Center For Excellence. University of Arizona Health Sciences