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
Like people, dogs are very susceptible to Valley Fever.
Dogs primarily contract Valley Fever in the low desert regions of
Areas in the
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
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
The telephone HOTLINE can be reached at (520) 629-4777
Our E-mail
address is:vfever@arl.arizona.edu
Our mailing
address is:
Mailstop
3601 S. 6 Th Ave.
Written by Lisa
Shubitz, D.V.M.