Coccidiodomycosis in Dogs: Signs, Symptoms and Diagnosis

Dog sitting with blankets in pick-up truck
credit: Cavan Images/Cavan/GettyImages

If you live in the southwestern United States, your dog could be at risk for a fungal infection called coccidioidomycosis or Valley fever. It's endemic to southern California, Arizona and southwestern Texas. Coccidioides immitis thrives in the sandy, alkaline soil of these semi-arid regions, and a dog only needs to inhale dust containing a handful of spores to become infected. Once the spores get into the body, they morph into an aggressive unicellular fungus or yeast. Young dogs, elderly dogs and those with weak immune systems are most at risk. Studies show that most dogs in endemic areas will pick up the fungus at some point in their lives, but most will not get the disease.

How is coccidioidomycosis contracted and what does it do inside a dog’s body?

Coccidioides enter a dog's body through inhalation of spores. They morph into dangerous yeasts that reproduce in the body by budding or fission, invading tissues, organs and the nervous system. Coccidioidomycosis can cause serious breathing problems, respiratory infections, swollen lymph nodes, painful sores and ulcerated skin.

My dog stopped eating and she's coughing. Can this be a sign of coccidioidomycosis?

With its vague symptoms, it's not easy to recognize the signs of coccidioidomycosis dogs. Symptoms are in direct proportion to the severity of the illness, and they are often only observable when it has reached the serious phase. Also, the more spores inhaled, the more severe the illness. It takes as few as 10 tiny spores to spark the disease. Clinical signs are body-specific and vulnerable sites include the bones, skin, eyes or the nervous system. It takes from one-to-three weeks for the infection to set in and the first wave of symptoms of coccidioidomycosis you may observe are:

  • Coughing
  • Respiratory distress with difficulty breathing.
  • Gagging or hacking when eating.
  • Pneumonia-like symptoms.
Coccidioidomycosis fungus, illustration
credit: KATERYNA KON/SCIENCE PHOTO LIBRARY/Science Photo Library/GettyImages

Body-specific symptoms of coccidioidomycosis or Valley fever when the disease disseminates.

In its disseminated form, coccidioidomycosis spreads to other parts of a dog's body. Symptoms correlate with the specific organs and tissues affected. Seek veterinary care at once if you see any of the following symptoms in your dog.

Symptoms of coccidioidomycosis in the bone: If the fungus extends into the bones (rigid organs that support and protect other organs) your dog may exhibit the following tell-tale signs of infection:

  • Lameness
  • Swelling of the joints and bones.
  • Obvious pain in the neck or back.
  • Abscesses may form over the infected areas of the bone.
  • Paralysis

Symptoms of coccidioidomycosis in the skin: Obvious signs will be draining or seeping lesions that won't heal.

Symptoms of coccidioidomycosis in the lymph nodes: Check for swollen and enlarged lymph nodes under the mouth, shoulder or knees.

Symptoms of coccidioidomycosis in the eyes: You may see inflammation, swelling of the eyes and vision problems.

Below are more coccidioidomycosis symptoms to be on the lookout for:

  • High temperature — your dog's normal body temperature should be 101-102.5-degrees Fahrenheit (A thermometer is a handy diagnostic tool to have in your dog's first aid kit.)
  • Lack of appetite.
  • Weight loss.
  • Extreme fatigue.
  • Weakness
  • Pneumonia
  • Seizures
  • Swollen testes.

A silent symptom of coccidioidomycosis is lung lesions, which are only discovered through thoracic X-ray at your veterinary hospital.

Brown Miniature Pinscher standing in field against sky
credit: Cavan Images/Cavan/GettyImages

How does a veterinarian diagnose coccidioidomycosis or Valley Fever?

A definitive diagnosis of coccidioidomycosis is challenging for veterinarians. The disease presents with so many symptoms that are like other illnesses. As well, symptoms are often vague — a common characteristic of pathogenic diseases.

Keep notes of the symptoms you observe in your dog. Changes in her behavior, appetite, and activity level are significant cues. And your veterinarian will evaluate this information along with your dog's medical history. A thorough physical examination checks the heart rate, blood pressure and body temperature. Diagnostic testing also includes a complete blood count (CBC), blood chemistry panel, urinalysis and stool sample.

X-rays of the chest, bones and joints are next. Cocci serology tests such as cocci titers, or Valley fever tests reveal the fungus. Other tests are fungal swabs from tissue samples, biopsy of tissues, fluids, or cells, CT scan and MRI.

If the tests are negative, your veterinarian may still suspect coccidioidomycosis. In this case, your dog will undergo the same round of tests a month later.

How is coccidioidomycosis treated and what is the prognosis for my dog?

If treated early, over 90 percent of dogs will recover from the illness within a few weeks. Or in the best case scenario, it may even resolve on its own. But, if your dog has a more severe, disseminated form of coccidioidomycosis, treatment needs to be aggressive and in most cases, long-term.

In dogs with bone lesions, treatment could continue for up to one year. The administration of oral antifungal agents, most commonly Fluconazole (Diflucan), is relatively easy on the liver and the typical treatment protocol. At one time, ketoconazole (Nizoral) was the most used antifungal medication. It must be given with vitamin C for full absorption and its main downside is potential side effects including lack of appetite, vomiting and diarrhea. A third commonly used antifungal drug, itraconazole(Sporanox), may be prescribed. It's costlier than ketoconazole, but so far, it's achieving positive results for dogs with the disease.

What can I do to prevent my dog from getting coccidioidomycosis?

As of 2018, no vaccines are available for coccidioidomycosis. However, you can take some preventive measures to cut the risk of infection for your dog, as follows:

  • Find out where there have been reports of coccidioidomycosis and avoid those areas.
  • Discourage your dog from stirring up dust by digging in the soil, and don't let him sniff the ground.
  • When it's hot outside, avoid walking your dog or letting her out after a rainfall.
  • You can prevent dust on your own property by installing ground covers such as grass, gravel, or mulch.
  • Avoid the use of immunosuppressive drugs whenever possible.
  • Ensure your immunosuppressed dog is under veterinary treatment.