VALLEY FEVER IN THE SONORAN DESERT

Valley fever is a disease caused by a fungus known as Coccidiodes immitis. Although the proper name for this disease is coccidioidomycosis, it is most often called valley fever, California disease, desert rheumatism, or San Joaquin valley fever.  It is caused by spores in the ground that become airborne.

Valley Fever (VF) spores are everywhere. Everyone inhales them all of the time. The determination about whether or person or animal contracts Valley Fever from the spores is totally dependent on their immune system.

The symptoms of Valley fever are:

• Lethargy
• Hacking cough
• Lack of appetite
• Lameness
• Fever

Though most cases are caused by inhaling the spores, direct inoculation is also possible.  This can result from stepping on a sharp rock or stick that contains the spores.  That version of VF is contained within a localized infection and becomes a sore that won’t heal.  If your dog presents with something of that nature, do have testing done to eliminate VF as a possibility.

Diagnosing VF is done in a methodical manner by veterinarians:

• Review animal history and look for clinical signs.
• VF test

1. Tests for antibodies—having antibodies does not confirm diagnosis as it may be from an earlier infection.
2. IgM antibodies typically develop shortly after an infection, are usually detectable within one to 3 weeks of the onset of symptom and start to disappear at about 5 weeks. As IgM antibodies fade, IgG antibodies set in.
3. IgG antibodies can remain detectable for up to a year after treatment. Antibody tests can aid in diagnosing VF as well as helping to differentiate it from other conditions that present with similar symptoms.

• CBC (complete blood count) will test for any other organ deficiencies.
• X rays—VF settles most commonly in the lungs but can also be found in the bones, eye, and brain
• Lung biopsy may be necessary.

The VF test can result in a finding of a titer such as 1:2, 1:4, 1:8, etc. up to 1:256 which is the highest titer that will evidence itself.  The VF titer number is most often of little consequence.  Dogs with a 1:4 can be symptomatic while a dog with a 1:128 titer may show no evidence of the disease.  It all goes back to the immune system of the dog being able to fight or succumb to the disease.

Treatment of Valley Fever

• The primary drug of choice to treat VF is Fluconazole (Diflucan). Fluconazole is the most well tolerated by most animals and can be combined with a number of medications that the dog may already be taking.  Fluconazole does not kill the fungus, but only weakens it.  Fluconazole is given twice per day and patients usually start to feel better in a few weeks.  This is a longer-term medication that typically requires treatment for 8 to 10 months.
• Ketoconazole and Itraconazole are other drugs that may be used alone or in conjunction with Fluconazole.
• Treatment with additional medications to reduce fever will help keep the animal more comfortable. Steroids or appetite stimulants may also be prescribed to help the dog eat.
• Amphotericin B is an injectable treatment for dogs that do not respond to conventional care and are more serious and life-threatening. This drug works by slowing the growth of fungi in the system.
• For typical treatment of VF, after 8 to 10 months, the dog should be taken off the drug for one month and then have a retest.
• Dogs with severe cases especially for those who evidence brain or bone disease may need to remain on fluconazole for life.

Supplements that are promoted to be effective against VF are not. They cannot target VF, nor the t-cells involved with the disease.  They may help slightly with immunity but are unlikely to have any real impact.

Any dog breed may develop VF, but Boxers seem to be especially vulnerable.  Areas near construction sites can certainly unearth spores.  Often after a haboob (dust storm), more cases become evident in 3 months’ time.  Rainstorms are responsible for aerosolization of spores giving way to further VF spikes.

The good news is that a Valley Fever vaccine will be available later this year.  Dr. Lisa Shubitz, at the University of Arizona Valley Fever Center for Excellence and the doctors at UC Davis in CA have made this possible.     At this point, the vaccine will be used to prevent VF, but it may be that it will help in treatment of the disease.  The evidence is that it is not just an antibody response but helping the dog’s own white cells do their job.  It does not contain a chemical stimulant making it safe for dogs who are immunosuppressed.   Veterinary offices and clinics will have more information as time goes on. 

Article written by Judy Smith, Vet Team Manager, RAGofAZ

Information courtesy of Dr. Josh Sosnow at North Scottsdale Animal Hospital, Scottsdale, AZ.