Dogs and Valley Fever

by Lisa Shubitz, D.V.M.

Coccidioidomycosis (also known as Valley fever, California valley fever, fungal pneumonia and (incorrectly) coccidiomycosis) is a fungal disease caused by Coccidioides immitis or C. posadasii. It is endemic in certain parts of Arizona, California, Nevada, New Mexico, Texas, Utah and northwestern Mexico.

C. immitis resides in the soil in certain parts of the southwestern United States, northern Mexico, and a few other areas in the Western Hemisphere. Infection is caused by inhalation of airborne, fungal particles known as arthroconidia, which are a form of spore. The disease is not transmitted from person to person. C. immitis is a dimorphic saprophytic organism that grows as a mycelium in the soil and produces a spherule form in the host organism.

Like people, dogs are very susceptible to Valley Fever. Dogs primarily contract Valley Fever in the low desert regions of Arizona, New Mexico and southwestern Texas and the central deserts of California. Dogs accompanying people traveling through these areas or wintering in these warm climates have about the same chance as their owners of being exposed. Valley Fever is not contagious, but is acquired from the environment by dogs and humans alike. Dogs contract Valley Fever by inhaling spores distributed by wind and construction, and probably by digging and poking their curious noses in rodent burrows. Many dogs become infected with Valley Fever but do not become visibly ill or have only mild symptoms that are overlooked by owners and go away on their own. A lot of dogs are not so lucky and get very sick from the fungus.

Areas in the U.S. where the Valley Fever fungus is found.

 

What Are the Symptoms of Valley Fever in Dogs?

 

Early symptoms commonly associated with primary disease are cough, fever, depression, and lack of appetite. Symptoms typically occur about 3 weeks after infection. Primary disease is limited to the lungs and may go away on its own, or the dog may become sick enough to require medication. In dogs, Valley Fever commonly spreads to other parts of the body. When this happens, the dog has disseminated disease and few will recover without treatment. Symptoms associated with dissemination of the infection are often related to the organs affected but commonly include lethargy, lack of appetite, weight loss, and persistent fever. In disseminated disease, the bones and joints are the most frequent targets. In these cases, lameness is the most common symptom. Occasionally, the fungus may invade the brain and seizures can result.

 

How is Valley Fever Diagnosed in Dogs?

 

Arrival at a diagnosis of Valley Fever requires suspicion of the disease from the history, symptoms, and various diagnostic tests. If your dog has recently visited an area where the fungus can be picked up, telling your veterinarian about your dog's travel history can be very helpful in deriving the diagnosis. Diagnostic testing includes blood tests, x-rays of the chest and painful or swollen bones and joints, and culture of body fluids and/or tissue for the fungus. Blood tests are performed to look for antibodies to the fungus, changes in blood cell counts, and involvement of body organs other than the lungs. Antibody tests, which are called serologies, cocci tests, or cocci titers, may be negative early in the disease and repeating them in 3-4 weeks is sometimes necessary. Culturing the fungus out of body fluids or organs is a highly specific means of diagnosis though it is usually difficult. Sometimes all the tests come back negative and more tests may have to be done to rule out other diseases. Persistence may be required to confirm a diagnosis.

 

What is the Treatment for Valley Fever in Dogs?

 

In most cases, a dog ill enough from Valley Fever to be seen by a veterinarian will require treatment with antifungal medication. Courses of medication are usually extensive, averaging 6-12 months. Dogs with bone disease or central nervous system (brain or spinal cord) involvement may require lifetime treatment with medication to keep symptoms from recurring.

The most common medication prescribed is ketoconazole (brand name Nizoral) and is the least expensive of a class of very expensive drugs. Side effects of ketoconazole include inappetance (sometimes difficult to distinguish from the disease itself), vomiting, and lightening of the coat. The coat changes are temporary and will reverse once the dog is off medication. Occasionally, a dog will have an adverse reaction to the drug, affecting the liver, and it will have to stop taking it. Newer drugs related to ketoconazole are itraconazole (Sporanox) and fluconazole (Diflucan). Both drugs are reported to have fewer gastrointestinal side effects and they may be more effective than ketoconazole; their big drawback is that they cost more. They are often used in animals who are not doing well on ketoconazole. For dogs that have disease known to be in their brain, fluconazole is the drug of choice.

Very ill dogs may require hospitalization and intravenous antifungal therapy. Fluconazole is available for intravenous infusion. Amphotericin B, an excellent antifungal drug, is only available for intravenous use but has the serious drawback of toxicity to the kidney. Newer formulations of amphotericin B with much lower kidney toxicity have recently become available but have not been extensively tested in animals.

 

Will My Dog Recover From Valley Fever?

 

The good news is that most dogs, with adequate antifungal therapy, do recover from this disease. The majority are able to get off medication and live a normal life. They are probably immune for the rest of their lives from a new infection, though sometimes an animal will have an old infection become active again. A small portion of animals must take medication for life, and another small portion, unfortunately, will die of Valley Fever in spite of drug treatment. This most commonly happens when there is a disseminated infection.

 

When Do You Stop Treatment?

 

Treatment of the Valley Fever in your dog is monitored by rechecks with your veterinarian and cocci serology tests every 2-4 months, if he/she is responding to the medicine and feeling better. It is very important to continue medicating your dog as directed until the veterinarian confirms that the blood tests are negative and tells you to stop medication. If you stop treating too soon, symptoms may recur. If symptoms recur after your dog is taken off medication, your veterinarian will probably recommend resuming treatment and may suggest the dog remain on medication for life.

 

Valley Fever in Other Animal Species

 

Valley Fever is a clinically important disease primarily in the dog, but some other species of companion animals may be severely affected by it as well. Cats are affected occasionally. Similar to dogs, llamas seem to be quite susceptible to illness. Llamas, however, are relatively unpopular where the fungus grows. Domestic livestock, while exposed to the organism, very rarely develop disease associated with it. Some of the small exotic mammals people keep as pets can contract it, though diagnosis in these animals is often after the fact. Zoo animals in Phoenix, Tucson, and San Diego have suffered pretty severely with Valley Fever over the years with the disease especially taking a heavy toll on the monkeys and apes.

 

Valley Fever Center for Excellence

 

In 1995, the Valley Fever Center for Excellence (VFCE) was established to promote education, research and quality patient care for Valley Fever. The Center is jointly sponsored by the University of Arizona and the Tucson Veterans Affairs (VA) Medical Center. We provide information to the public, physicians consultations with VFCE physicians and physician referrals for patients. In 1996 an association was created with the University of Arizona Department of Veterinary Science and a veterinarian was added to our staff. Due to the paucity of information on Valley Fever in dogs, public information on dogs was added to the VFCE's resources. While evaluations of dogs are not performed through the VFCE, questions are fielded by our staff veterinarian with the Department of Veterinary Science. Referrals for evaluation to a veterinary internal medicine specialist are available.

The telephone HOTLINE can be reached at (520) 629-4777

Our E-mail address is:vfever@arl.arizona.edu

Our mailing address is:

Valley Fever Center for Excellence
Mailstop 1-111
3601 S. 6 Th Ave.

Tucson, AZ 85723

Written by Lisa Shubitz, D.V.M.