Valley Fever in Dogs: What You Need to Know

Veterinarian checking dog valley fever


You’ve undoubtedly heard of dog valley fever, but do you know what it is? It’s a common respiratory disease in the southwestern United States. Each year, thousands of humans and pets are affected by it. Dogs usually recover from this disease. In rare cases, the infection is high enough to cause a life-threatening condition for them. If left untreated in such a case, the infected dog may die. Here’s all that you need to know about canine valley fever. 


What is Valley Fever in Dogs?


Valley fever is a respiratory infection in dogs that is caused by the fungus Coccidiodes immitis. Scientists call this disease “Coccidioidomycosis”, but it’s commonly known by names like “Valley fever”, “desert rheumatism”, “California disease”, or “San  Joaquin Valley fever”. The infection usually affects the lungs of the dogs, but it can disseminate to other organs in severe cases. 


Humans, cattle, monkeys, fish, horses, and several other animals are susceptible to this infection. However, the reason why dogs are particularly vulnerable to this disease is because of their sniffing instinct. The spores of Coccidioides are found in the soil, and a dog inhales them while sniffing the ground. 


Prevalence of Valley Fever


Valley fever is prevalent in some areas of Arizona, New Mexico, California, Colorado, Nevada, Oklahoma, Texas, and Utah. Apart from the Southwestern United States, the infection rate is also high in some parts of Mexico and Central and South America. Some cases have also been reported in South-central Washington. The fungus has adapted to living in the desert-like climate of these areas.


Dog in desert Arizona


Despite its overall prevalence, infection rates may differ at the county level. However, the factors influencing these infection rates have not been properly identified yet. The number of cases also differs from season to season. The majority of cases are reported in the late summer and early fall. 


Transmission of Valley Fever


The inhalation of spores of Coccidioides causes valley fever in dogs. The dogs may catch the fungus directly from the contaminated soil while sniffing. Sometimes, animals may inhale the spores that have been dispersed in the air. The infection is not contagious and there’s no animal-to-animal transfer of this disease. So, neither the dogs nor the humans can catch this infection from one another. 




“Coccidioides immitis” is a filamentous soil-dwelling fungus that produces spores. When a dog inhales the spores, they transform into spherules inside its lungs. The mature spherules burst and release more spores. The cycle continues until the lungs are filled with spherules. It results in pneumonia and several other respiratory complications. 


In a healthy dog, the immune system may control the dissemination of spherules. But if a dog is immunocompromised, the spherules can eventually migrate from the lungs to other organs of the body. This condition is called disseminated coccidioidomycosis and is life-threatening for canines. In particular, if the infection spreads to the nervous system, there’s no coming back from it. 


Symptoms of Valley Fever in Dogs


Some common signs and symptoms of valley fever in dogs are:


  • Persistent high fever
  • Shortness of breath 
  • Headache 
  • Swelling and pain in the joints
  • Lethargy 
  • Lameness 
  • Abdominal pain 
  • Diarrhea
  • Anorexia (loss of appetite)
  • Coughing 
  • Depression 
  • Malaise (weakness and discomfort)


Rare symptoms of the disease in cases where it has been disseminated are:


  • Erythema (skin rash)
  • Ulceration of the skin
  • Eye disease or blindness
  • Nervous disorders like seizures, etc.


Diagnosis of Valley Fever in Dogs


If you live in a Coccidioides prevalent area and your dog is showing any symptoms of fever, you must get him diagnosed. You need to take him to the vet right now. If your dog has begun to show symptoms of valley fever after you’ve returned from a trip to the southwest US, inform your vet about your travel history. 


The vet will probably begin the diagnosis by recommending some laboratory tests. These will confirm whether your dog has valley fever or not. These tests may include antibody testing, blood tests, urinalysis, biochemistry profile tests, or X-rays. Antibody tests like ELISA or titer tests will confirm the presence of fungus. Microscopic examination of sputum or tissue samples is another method to do so. After confirmation, blood testing and X-rays of the chest will determine the amount of infection. 


Treatment and Prognosis of Valley Fever in Dogs 


Many antifungal medications can effectively treat valley fever in dogs. Some of the most common antifungals prescribed for valley fever are:


  • Ketoconazole (brand name Nizoral®)
  • Itraconazole (brand names Itrafungol® and Sporanox®)
  • Fluconazole (brand name Diflucan®)


The amount of infection will determine how long the antifungal treatment will last. In most cases, dogs begin to recover within two to three weeks of treatment. Usually, 6 to 12 months of treatment will be adequate and allow the dog to recover completely. A few dogs may die if the infection spreads. Especially, if the fungus has been disseminated to the nervous system, no antifungals are effective against it. 


Final Thoughts on Valley Fever in Dogs


Valley fever is a respiratory infection in dogs and humans that is prevalent in the southwestern US. It is caused by a fungus and spreads through inhalation of fungal spores. If you suspect your pooch is suffering from this condition, take him to the vet immediately. If you live in a disease-prevalent area, you must prevent the incidence of infection at all costs. We suggest you keep your pooch indoors and prevent his contact with the soil outdoors.

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