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Do Dogs Get Valley Fever?
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Symptoms
of Valley Fever in Dogs
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Diagnosis of Valley Fever
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Treatment of Valley Fever in Dogs
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Prognosis/Outcome for Dogs with Valley Fever
Prevention
of Valley Fever in Dogs -
Valley Fever in Other Animal Species
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Valley Fever Center for
Excellence
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PowerPoint Presentation
Do Dogs Get Valley Fever?
Yes, dogs get Valley Fever! 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 infected.
Areas in the US
where the fungus is found
Dogs comprise
the majority of Valley Fever cases in
animals. However, other animals can get the disease as well.
Cats, llamas, non-human primates, horses, zoo animals, and even wild animals
have been reported with Valley Fever. For more information on Valley
Fever in other species, go to Valley Fever in Other Animal
Species.
Valley Fever is caused by a fungus that lives in
the desert soil in the areas described above. As part of its life
cycle, the fungus grows in the soil (saprophytic cycle) and matures,
drying into fragile strands of cells. The strands are very delicate,
and when the soil is disturbed - by digging, walking, construction, high
winds - the strands break apart into tiny individual spores called arthroconidia
or arthrospores. Dogs and people acquire Valley Fever by
inhaling these fungal spores in the dust raised by the disturbance.
The dog may inhale only a few spores or many hundreds.
Used with permission: Dr. H. Levine
Once inhaled, the spores grow into spherules
(parasitic cycle) which continue to enlarge until they burst, releasing
hundreds of endospores. Each endospore can grow into a new spherule,
spreading the infection in the lungs until the dog’s immune system surrounds
and destroys it. The sickness Valley Fever occurs when the immune
system does not kill the spherules and endospores quickly and they continue
to spread in the lungs and sometimes throughout the animal’s body.
About 70% of dogs who inhale Valley Fever spores
control the infection and do not become sick. These dogs are asymptomatic.
The remainder develop disease, which can range from very mild to severe
and occasionally fatal.
Symptoms of Valley Fever in Dogs
 Click on image
primary pulmonary Valley Fever in dogs are:
- coughing
-
fever
- weight loss
- lack
of appetite
- lack of energy
Some
or all of these symptoms may be present as a result of infection
in the lungs. As the infection progresses,
dogs can develop a severe pneumonia that is visible on x-rays. Sometimes
the coughing is caused by pressure of swollen lymph nodes near
the heart
pressing on the dog’s windpipe and irritating it. These
dogs sound like they have bronchitis.
 Additional
symptoms develop when the infection spreads outside the lungs
and causes systemic or disseminated disease.
This form of Valley Fever is almost always more serious than
when it is only in the lungs. Signs of disseminated Valley
Fever can include:
-
lameness or swelling of limbs
- back or neck pain
- seizures and other manifestations of central
nervous system swelling
- soft swellings under the skin that
resemble abscesses
- swollen lymph nodes under the chin, in front
of the shoulder blades, or behind the stifles
- non-healing skin
ulcerations or draining tracts that ooze fluid
- eye inflammation
with pain or cloudiness
Some of these symptoms are very rare and most need
to be differentiated from other diseases of dogs. Still
other signs can develop that are referable to affected internal
organs and may only
be detected by your veterinarian. While the lungs are
the most common site of Valley Fever in dogs, it can infect
almost
any tissue of the body.
Sometimes a dog
will skip any signs of having a primary infection in the lungs and only develop
symptoms of
disseminated disease, such as a swollen, lame leg but no coughing or fever,
or fever,
weight loss, and a draining tract, but eating and not coughing.
Symptoms of Valley
Fever in cats
Cats can
manifest the same signs as dogs, but fewer cases occur in cats (estimate
1 cat case for every 50 dog cases)
and there is not as much information on them. Cats are often more ill
than dogs at the time of diagnosis. Unexplained weight loss, sometimes
without any other overt illness, can be a sign of Valley Fever in a cat. Skin
ulcerations that don’t heal may be more common in cats
than in dogs and may be sufficient reason to run a Valley Fever
test on a cat. Diagnosis
may also be obtained by performing a biopsy on the skin lesions.
FAQ - Is Valley
Fever contagious from animal to animal or animal to human?
Valley Fever is considered a noncontagious disease. Even
if multiple animals or humans are affected in a household, each infection was
acquired by inhaling spores from the soil. Coughing cannot spread it between animals or people.
In the case of draining lesions, the form of the organism in
the fluid is not considered to be infectious to people or animals. Nevertheless,
such lesions are best handled by bandaging. Bandages
should be changed daily or every other day and discarded
in outside
waste containers to minimize
risk of contaminating the environment. For
immunocompromised persons living in a household with a
pet that has a draining lesion, it is best to consult
your physician regarding this issue.
Diagnosis
of Valley Fever
Diagnosis of Valley Fever requires suspicion of the disease from the dog’s
history, its symptoms, and the results of examinations and tests performed
by your veterinarian. If your dog has recently visited an area where
the fungus can be acquired, telling your veterinarian about your dog’s
travel history can be very helpful in deriving the diagnosis.
In addition to examining your dog, your veterinarian
is very likely to order diagnostic tests to help identify the Valley Fever
infection. Common tests include:
- blood tests and
blood cell counts
- chest x-rays
- bone and joint
x-rays
- Valley Fever
blood test (also called cocci test, cocci serology, or cocci titer)
Sometimes tests are negative early in the infection,
especially the Valley Fever blood test, and they may need to be
repeated in 3-4 weeks to establish the diagnosis.
In difficult cases, the routine tests are not very
helpful in the diagnosis. Your veterinarian may recommend other
tests to find out what is making your dog sick. These tests
are often more definitive:
- Culture of fluid or tissue samples from your dog
to isolate and identify the fungus; this is highly specific
- Microscopic
examination of cell, fluid, or tissue samples to visualize
fungal organisms and inflammation in your dog
If your dog is having seizures or other signs of
neurological disease, your vet may urge you to get a
- CT or MRI
scan of the brain or spinal cord.
Usually Valley Fever is easily confirmed with basic diagnostic tests, but
occasionally it may be difficult to diagnose. In those cases, persistence
and advanced diagnostics will be required to rule out other diseases and
confirm Valley Fever.
Diagnosis
of Valley Fever in cats is the same as for dogs.
FAQ - When does
my dog need a Valley Fever test?
If your
dog lives in a region where Valley Fever is typical, your dog could need
a Valley Fever test for any illness that manifests the common clinical
signs - coughing, fever, weight loss, etc. In addition, your dog will
need some serum chemistries and white blood cell counts and sometimes x-rays
to aid in diagnosing the illness. A positive test in and of itself
is often not enough to diagnose Valley Fever.
For dogs that do not live in regions with Valley
Fever but have traveled through or spent time in one, a Valley Fever test
may be indicated for undiagnosed, unresolving illnesses. If your
dog becomes ill outside the typical locations for Valley Fever, it is
important to tell your veterinarian of your dog’s travel history.
FAQ - What
is a Valley Fever test/titer and what does it mean?
A Valley
Fever test, Cocci test, or Cocci titer checks the blood
to see if your dog is making antibodies against the Valley Fever fungus. If
the test is positive, it means your dog has been exposed to the fungus.
If the Valley Fever test is positive, the laboratory
then performs a titer. The titer measures how much antibody
your dog is making against the fungus. A titer is obtained by doubling
dilutions of the positive blood (1:4, 1:8, 1:16, 1:32 . . .) until the
test becomes negative. The titer that is reported to your
veterinarian is the last positive dilution. In broad terms, a higher titer is equated with
more severe disease. However, some very sick animals have low titers,
or even negative tests. For these dogs, other diagnostic tests are
necessary for diagnosing the illness. X-rays, blood cell counts, biopsies,
and microscopic examination of cellular specimens are a few of the tests
your veterinarian may need to run. Asymptomatic dogs (infected but not showing any
illness) may also have low titers, such as 1:4 or 1:8, sometimes 1:16. The
titer is helpful in diagnosing Valley Fever in sick dogs, but other tests are
usually needed to confirm diagnosis. Titers usually reduce over time as the animal’s
disease regresses. Dogs that start with low titers (1:4 or less than
1:4) may undergo little change in the titer. This is probably not
to be interpreted that your dog is not getting well. Monitoring your
dog’s symptoms and other tests, such as blood counts and x-rays, will
be better determinants of improvement in cases with low titers. Some dogs will remain positive with a low titer
for life. Continued treatment and monitoring of these animals
needs to be determined by your veterinarian on a case by case basis.
Treatment of 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 disseminated disease in bones, skin, or internal organs usually
require longer courses of medication. Central nervous system (brain
or spinal cord) involvement frequently requires lifetime treatment with
medication to keep symptoms from recurring.
Oral antifungal
medication in the form of daily pills or capsules is the usual treatment
for Valley Fever. There
are three common medications used to treat Valley Fever in dogs.
Ketoconazole (Nizoral)
is the most commonly prescribed and the least expensive. Incidence of side effects is
relatively high and the drug is usually administered twice daily with food. Absorption
is an issue on an empty stomach and acidification usually improves
uptake.
Itraconazole (Sporanox)
is expensive with a moderate incidence of side effects. Administration is once to twice
daily with food. Absorption is usually poor on an empty stomach.
An oral liquid formulation with much better absorption is available and
might be indicated for animals who are not eating very well but need this
medication. However, expense may be an issue.
Fluconazole (Diflucan)
is expensive with a low incidence of side effects compared to the other
two medications.
It is administered once or twice daily. Absorption is excellent
even on an empty stomach and this drug is often a good choice for very
sick dogs that aren’t eating well. Fluconazole is the drug of choice
for dogs and cats with infection of the brain, spinal cord, or eyes as it
is the only drug that crosses into those tissues.
Other
treatments for Valley Fever are mainly directed at supportive care: making
your dog feel better while the antifungal medication
starts to heal the infection.
- Cough suppressants - the cough may be so severe
that your veterinarian will prescribe medicine to relieve it.
- Pain and fever
relief - anti-inflammatories or pain medication prescribed by
your veterinarian may greatly help your dog’s
attitude and appetite during the severe stages of the disease.
- Nutritional
support - while some dogs eat reasonably well with Valley
Fever, others will shun food entirely. These patients
may need measures taken to get nutrition into them.
- Hospitalization -
dogs that are too sick to eat and drink and are becoming dehydrated
or are in severe respiratory distress
may need 24-hour care, intravenous fluids, oxygen, or other medication
that can only be given in the hospital environment.
Amphotericin B, is
an old but very effective antifungal medication that is mainly used for extremely
sick dogs
in today’s
veterinary practices. Amphotericin B is only available for intravenous
administration and has the serious drawback of toxicity to the kidneys. Newer
formulations of amphotericin B (lipid-complexed amphotericin
B - brand names: Abelcet; Ambisome) with much lower kidney toxicity
have recently become available. For dogs that are either very ill
with Valley Fever or dogs that are not recovering on oral medication, intravenous
treatment with amphotericin B, especially one of the newer lipid formulations,
may be indicated. Cost is very high.
Drugs very recently introduced to the market for
treatment of fungal disease in humans include:
- Voriconazole (Vfend)
- Caspofungin (Cancidas)
The role of these drugs in treating human Valley
Fever is not yet clear. They are likely cost-prohibitive for
use in animals at this time, as well as of unknown efficacy and safety,
but
they may have a role in the future for treating dogs.
FAQ - What is the
best treatment for Valley Fever?
Treatment choices vary by the individual veterinarian
and patient. Reasons for choice of medication include practitioner’s
experience with the drugs, costs, side effects, efficacy, severity of illness,
and convenience to the owner. If one medication is unsuccessful,
another will often be tried.
For disease of the brain and spinal cord, fluconazole
(Diflucan) is the drug of choice. Fluconazole is also the only drug
that penetrates tissues of the eye and should be employed in ocular cases.
FAQ - What is the proper dose of Valley Fever medications?
Your veterinarian is skilled in the diagnosis and
treatment of your pet’s illness. Should you feel that your dog is
not responding or may have side effects to the medicine, you should first
discuss your concerns with your veterinarian. If the results are not
satisfactory, you can seek a second opinion.
FAQ - What are
the side effects of oral Valley Fever drugs (ketoconazole, itraconazole,
and fluconazole)?
Ketoconazole (Nizoral) has the highest incidence
of side effects. Loss of appetite is the most common and may be severe
in some dogs. Others include lightening of the haircoat (may grey
in blacks), vomiting, diarrhea, elevated liver enzymes, and reduced fertility
of males. Giving the drug with food may reduce gastrointestinal side
effects as well as improving absorption of the medicine.
The coat color effects reverse with discontinuation
of the medication (with the exception of a few black dogs this author has
heard about that have remained grey).
Liver enzymes are monitored by routinely testing
your dog’s blood. If your veterinarian determines that they
are significantly elevated, the medication may be stopped or the dose decreased.
Itraconazole (Sporanox) may also cause lack
of appetite and GI signs, though with less frequency than ketoconazole.
It may increase liver enzymes. Occasionally, itraconazole can
cause ulcerated lesions of the skin. If this happens, a reduction
in dose may clear it up, or your dog may need to be treated with a
different medication.
Monitoring of liver enzymes is as for
ketoconazole.
Effects of itraconazole
on coat color are unknown by this author but may be similar to ketoconazole in
an occasional dog. Itraconazole
is not known to affect fertility of males.
Fluconazole (Diflucan) has the fewest side
effects. Gastrointestinal signs can occur, though are often mild,
and elevations in liver enzymes are relatively uncommon. Unlike itraconazole
and ketoconazole, fluconazole is mainly eliminated by the kidneys.
Dose reductions may be needed in animals with poor kidney function.
Liver enzymes also need to be monitored because of occasional problems with
enzyme elevations. Fluconazole has minimal to no effect on male
fertility.
All the oral Valley Fever drugs cause birth defects
in fetuses and should be avoided in pregnant animals unless the benefit
to the mother outweighs any risk to the fetuses.
FAQ - Are there vitamins, nutritional supplements, or alternative
therapies for pets with Valley Fever?
Most
ill dogs could receive a pet multivitamin supplement safely and possibly
with benefit to overall well-being. Vitamin C is often prescribed
to be administered with ketoconazole. This aids absorption of the
drug by helping to acidify the stomach and may also “boost” the dog’s immune
system. Use of the vitamin C should be checked with your veterinarian
as high doses may cause gastrointestinal irritation.
Talk to your veterinarian about your dog’s overall
nutrition status and the nutritional goals you need to meet while your
pet is ill. The more ill your dog, the more important it is to discuss
this issue with your vet.
For dogs that will eat nothing at all, force feeding
may be an option to attempt to meet nutritional needs. For help
in determining if this drastic measure should be taken and what food should
be used to implement it, talk to your veterinarian. Force feeding
is a big commitment and an unpleasant venture for both dog and owner, but
in occasional situations it may mean the difference between recovery and
loss of the dog. If the dog’s nutritional needs can’t be met any other
way, surgical placement of a feeding tube may be an alternative.
Alternative
therapies, such as herbs or acupuncture, have not been scientifically
tested against Valley Fever. If you
wish to pursue alternative treatments, this author recommends you consult
a veterinarian trained in holistic medicine. These professionals
are your best source of help.
For cats, it is highly recommended that
no herbs or supplements be given without the guidance of a veterinarian.
Cats have a much different metabolism than dogs and what might be harmless
in a dog could prove very toxic to a cat. For cats that won’t eat
at all while sick, surgical placement of a feeding tube may be necessary
to make sure the cat does not develop fatty liver syndrome because of the
lack of food intake.
Prognosis/Outcome for Dogs with Valley
Fever
Will My Dog Recover
From Valley Fever?
The
good news is that most dogs, with adequate antifungal therapy, do recover
from this disease, especially with early diagnosis and intervention.
Dogs with infection only in the lungs have the best prognosis for recovery
and usually respond the quickest to treatment.
Dogs with disseminated infection almost always
have a more guarded prognosis. As with lung infections, it seems
that the majority respond well to medication and lead normal lives. A
small proportion of animals must take medication for life, and another small
number, unfortunately, die of Valley Fever in spite of drug treatment.
For dogs that are seriously ill, requiring hospitalization
and supportive therapy, the prognosis can be grave. With aggressive
treatment, possibly including intravenous antifungal medication, some dogs
will get well.
Dogs with central nervous system disease (seizures,
etc) also carry a guarded prognosis. Among those that respond to
medication, about 80%, most will remain well with fluconazole (Diflucan),
but treatment may be required for life.
In animals with severe bone infections and the
pain that goes with them, pain relief will often provide the support needed
to allow the Valley Fever medication time to take effect. Treatment
of high fevers with anti-inflammatories is helpful, also, as fever reduction
can improve the appetite and energy level of the dog. Pain medicine
and anti-inflammatories can be prescribed by your veterinarian.
Some dogs do not recover in spite of everyone’s
best efforts, either due to the severity of illness at the time of diagnosis
or because of long-standing, poorly responsive disease. Fortunately,
these animals represent a minority of dogs with Valley Fever.
Statistics
regarding how many dogs recover compared to those which do not are not available.
Stopping Treatment
Treatment of the Valley Fever in your dog is monitored by rechecks with
your veterinarian. Your veterinarian will examine your dog to look
for improvement as well as performing blood tests and possibly x-rays to
monitor progress and make sure the medication is not harming your dog.
If your dog is very ill, rechecks may be frequent at first. As the
disease stabilizes and recovery becomes apparent, your veterinarian will
probably only need to evaluate your dog every 2-4 months.
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.
FAQ - Can
Valley Fever relapse and can dogs be reinfected?
Valley Fever is well known to relapse in both humans
and dogs. In particular, cases of disseminated infection have a
30-50% rate of relapse in humans, no matter how well the initial infection
was treated. It is not known how many canine cases of Valley Fever
relapse, but relapses are not uncommon.
In the case
of a relapse, a return to medication is usually enough to make symptoms
subside, but the dog may require several
additional months of treatment. Dogs that experience more than one
relapse or get very sick with the relapse should probably have lifetime
treatment with medication considered.
Reinfections in humans are documented only rarely. It
is not known at this time whether dogs are susceptible to reinfection.
Prevention of Valley Fever in Dogs
Currently,
there is no sure fire way to prevent Valley Fever in pets short of never
residing in or traveling through the areas where the fungus grows.
Valley Fever endemic areas are among the fastest growing regions in the
country right now, which makes encounters of animals and people with the
fungus a likely event.
Things you can do to reduce the likelihood of your
dog’s exposure to the fungus are to avoid activities that generate dust,
reduce digging behavior by dogs, prevent sniffing in rodent holes, and
keep dogs indoors more than outdoors. Treating the soil is currently
not practical as the fungus lives in spotty areas and can live up to 12
inches deep in the ground. Yard ground cover that reduces dust, however,
is helpful: grass and deep gravel or other dust-controlling cover.
A vaccine is under development. It is possible
a vaccine will be available in the future to prevent Valley Fever or make
it only a very mild illness in dogs. Vaccination against Valley
Fever would be very useful for animals traveling to places like southern
Arizona and southern California as well as those dogs that live in these
places.
Valley
Fever in Other Animal Species
Valley Fever can affect many other animals besides dogs. Most mammals
can be shown to be infected with the fungus, even if they do not get sick
from it very often. Species in which Valley Fever has been found
include:
- cattle and other livestock
- horses
- llamas
- apes and monkeys
- many kinds of zoo animals such as kangaroos, wallabies,
tigers, bears, badgers, otters, etc.
- marine mammals - sea otters and dolphins
- occasional wildlife that lives
in the endemic area - skunk, cougar, javelina
Valley Fever
can be what is considered an “incidental
finding” after death: the organisms are present but are not causing the
disease Valley Fever in the animal. This is very typical of cows
and other ruminant livestock. Occasionally, a livestock animal
may become sick and die from the illness but it is very rare.
Clinical infections
are uncommon in horses but if
they manifest the disease, it is usually disseminated at the time of discovery.
Of the 20 or so cases reported in the literature, one was treated successfully.
The remainder were euthanized. As most of the case reports are old
and the medications currently available are both more efficacious and more
economically feasible, treatment of horses today may be more successful.
Llamas,
which are difficult to decide whether to call livestock or exotic pets,
appear to be exquisitely sensitive to
Valley Fever, unlike most other hoofed species. They develop severe
and fulminant disease. Death is the usual outcome. This author
is unaware of successful treatment at this time, but your own veterinarian
that treats your llamas may have experience treating the infection.
Cats have many fewer infections than dogs
and information on cats is interspersed with the canine information above
as diagnostic and treatment information for canines is relevant to this
species as well.
Apes, monkeys,
and all other smaller primates are very susceptible to Valley Fever. Many
of the animals in the Phoenix, Tucson, and San Diego zoos, as well as primates
in centers
and refuges that exist in the endemic area, are being treated long term
for Valley Fever, and the zoos lost many of these creatures before treatments
for Valley Fever were developed. Treatments are the same as for
dogs and people.
Other zoo animals, most of which are exotic to
this part of the country, are variably susceptible to the disease.
The zoos are very aware of this disease and often get early testing of
animals that are not feeling well. The animals can then be medicated.
Unusual cases crop up periodically in marine mammals
such as sea otters and dolphins, suggesting the spores can be blown out
over the water where these animals inhale them and become sick. An
occasional case is also found in wild native animals. Likely, these
animals have become debilitated in some way, making them susceptible to
the disease. The infection is discovered after the animal has died
or been euthanized for poor condition.
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 to veterinary specialists for evaluation are
available.
You may contact us:
e-mail:
vfever@email.arizona.edu
postal-mail:
Valley Fever
Center for Excellence
Mail Stop 1-111 INF
3601 S 6th Ave.
Tucson, AZ 85723
Telephone HOTLINE:(520) 629-4777
Written
by Lisa Shubitz, D.V.M.
Copyright © 2004 Valley Fever Center For Excellence.
All rights reserved.
Revised: April 27, 2004 .
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