By Dr. Becker
Today, I'm going to discuss a disease with a very long name – coccidioidomycosis, also known as valley fever.
Coccidioidomycosis is an infection caused by the Coccidioides immitis fungus. It is an uncommon but deadly disease that primarily occurs in dry, hot climates like those found in parts of the western and southwestern U.S., especially Southern California, Arizona, southwest Texas, New Mexico, Nevada, and Utah, as well as in Central and South America. Coccidioidomycosis is also known as California fever, desert fever, and most commonly, valley fever.
Coccidioidomycosis can affect many types of mammals, including humans. It occurs more often in dogs than cats. The condition is not zoonotic, meaning it can't be passed from animal to human or human to animal.
How Dogs Acquire Valley Fever
The Coccidioides immitis fungus is found in upper layers of soil, but several inches deep where it can withstand high temperatures and lack of moisture. The fungus works its way to the surface after a rainy period or soil disturbance of some kind. Once on the soil's surface, the fungus forms spores that are spread by wind and dust storms.
Pets can acquire coccidioidomycosis from inhaling the soil-borne fungus. Dogs susceptible to the infection can become ill from as few as 10 fungal spores.
The infection starts in the respiratory tract and then frequently spreads to other body systems. In the lungs, the spores are round globules that exist as parasites until they grow big enough to break open, releasing hundreds of endospores that travel to other tissues, and continue the process of growing, rupturing and spreading throughout the body.
If the endospores get into the lymphatic and circulatory systems, they create a systemic infection. Coccidioidomycosis sets in from one to three weeks after exposure.
Dogs who are outdoors a great deal are at highest risk for valley fever – especially dogs that have lots of space to roam. Large dogs seem more at risk, but it could be because they tend to spend more time outdoors than smaller dogs.
Some dogs can develop immunity and never show any symptoms -- especially younger dogs. When symptoms do occur, they include fever, coughing, difficulty breathing, lethargy, lameness, swelling of bones or joints, significant weight loss with muscle wasting, enlarged lymph nodes, skin ulcers and draining sores, inflammation of the cornea or iris of the eye, seizures, and heart failure.
It's not unusual for valley fever to spread throughout the body, affecting bones and joints, eyes, skin, liver, kidneys, central nervous system, cardiovascular system, and reproductive organs (specifically the testes).
Cats usually don't exhibit the same symptoms as dogs do, and frequently show no symptoms at all until the infection has spread significantly. In cats, the deeper layers of skin tissue are more often affected, so symptoms like masses, abscesses, and lesions with draining are more common in kitties.
Diagnosis and Treatment
Your veterinarian should do a careful physical exam and perform a complete blood count, chemical blood profile and urinalysis. You'll need to provide a history of your pet's health and symptoms, including possible opportunities for exposure to the Coccidioides immitis fungus.
Treatment of valley fever depends on the extent of the infection and clinical symptoms. If the condition is widespread, traditional treatment involves aggressive anti-fungal therapy for up to a year. Other drugs, including cough suppressants and steroids, may also be prescribed to treat individual symptoms. In dogs that aren't responding well to drug therapy, a drug level measurement test can be performed to determine how well the medication is being absorbed.
Integrative veterinarians will often combine traditional anti-fungal therapy with more natural modalities like cytokine therapy, medicinal mushrooms, IV vitamin C therapy, and ozone therapy.
Affected dogs should be fed a high quality species-appropriate diet, preferably fresh, to help maintain body weight. Activity should be restricted until symptoms begin to subside.
Antibodies should be monitored every three to four months until they return to a normal level.
Unfortunately, valley fever is one of the most dangerous of the fungal diseases, and the prognosis for most dogs is guarded or grave. Sadly, while many dogs improve following a course of anti-fungal drug therapy, relapse is common.