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Valley Fever in Dogs

Dog in desert
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Severity: i High
Life stage: All

Valley Fever in dogs is a serious disease caused by exposure to the fungus Coccidioides immitis. Symptoms can range from cough, fever, and lethargy to more severe signs such as weight loss, seizures, and loss of coordination. Symptoms typically appear 1-3 weeks after exposure. Not all dogs will develop symptoms that require treatment. 

Valley Fever, also known as coccidiomycosis, is a fungal infection in dogs. Infection occurs when an animal is exposed to the fungus Coccidioides immitis.

This fungus is localized to certain geographic areas, meaning that your dog’s risk of contracting Valley Fever is based largely on where you live. In areas where the fungus is present, a relatively high number of dogs will become infected at some point during their lifetime, but only a percentage will develop symptomatic signs that require treatment. 

What is Valley Fever in Dogs?

Valley Fever is a disease that is caused by the fungus Coccidioides immitis. While many infections with this fungus are asymptomatic (do not show symptoms) and clear up spontaneously, some infected dogs go on to develop Valley Fever. Signs of illness range from a mild upper respiratory tract infection to a wide-spread disease affecting the brain, bones, and other internal organs.

Traditionally, Valley Fever has been found primarily in Central and South America and the Southwestern United States. However, in recent years, the distribution of this fungus has begun to spread to other geographic areas, including as far north as Washington State. Talk to your veterinarian to determine whether Valley Fever is a concern in your geographic area.

How Do Dogs Get Valley Fever?

Dog sniffing in the desert

The fungus that causes Valley Fever, Coccidioides immitis, is found in the soil. It can remain dormant for long periods of time, even at high desert temperatures. When the soil is disturbed by weather, fungal spores can aerosolize (be released into the air) and be inhaled by people and pets. Dogs may also contract coccidiomycosis by digging in the dirt or using their noses to investigate rodent burrows.

Valley Fever is most common in young, male, large breed dogs, especially those that are permitted to roam freely outdoors (as opposed to being leash-walked on sidewalks). Valley Fever appears to be especially prevalent in Boxers and Doberman Pinschers.  

Is Valley Fever Contagious in Dogs?

While Valley Fever can infect people and other pets (including cats, horses, and even some exotic pets), it is not considered a contagious disease. Your dog cannot transmit Valley Fever to you or other household pets through coughing or contact, and you cannot transmit Valley Fever to your pets. 

Any dog infected with the disease came into direct contact with Coccidioides immitis.

Valley Fever Symptoms in Dogs

Valley Fever can be divided into two separate clinical forms: primary and disseminated. In primary Valley Fever, clinical signs of illness are confined to the lungs. In disseminated Valley Fever, however, the fungus spreads throughout the body. This results in clinical signs affecting a wide range of body systems. 

Valley Fever may be difficult to distinguish from kennel cough or pneumonia in dogs. 

Signs of primary Valley Fever include: 

  • Cough
  • Fever
  • Lethargy
  • Decreased appetite

Disseminated Valley Fever, in contrast, is a more severe condition. Affected dogs may demonstrate a variety of symptoms, depending on where the fungus has spread within their body. Signs of disseminated Valley Fever may include:

  • Weight loss
  • Nosebleed
  • Seizures
  • Altered mental state
  • Pacing
  • Ataxia (stumbling as if drunk)
  • Limb weakness (limping) or paralysis
  • Blindness 
  • Eye inflammation
  • Lameness
  • Painful, swollen joints 
  • Back or neck pain
  • Swollen lymph nodes
  • Non-healing skin wounds
  • Draining wounds

While many infections with Coccidioides immitis are asymptomatic, symptomatic Valley Fever is a serious medical condition. Disseminated Valley Fever, in particular, requires urgent treatment. If a dog develops Valley Fever, signs of illness typically develop one to three weeks after exposure to the fungus. 

Diagnosing Valley Fever in Dogs

Boxer dog at the vet

There are a number of tests used to diagnose Valley Fever in dogs, but each of these tests has limitations. In most cases, obtaining an accurate diagnosis will require a combination of tests. 

Your veterinarian will begin by performing a thorough physical examination of your dog. By examining your dog from nose to tail, including listening to your dog’s heart and lungs, your veterinarian will be able to zero in on particular areas of concern that may be causing your dog’s illness. 

Next, your veterinarian may perform a complete blood cell count (CBC), serum biochemistry profile, and radiographs (X-rays). These tests are used to begin narrowing down the list of potential causes for your dog’s signs of illness. Dogs with Valley Fever often have bloodwork changes that suggest infection. Radiographs of your dog’s chest may show changes that suggest the presence of fungal pneumonia.

If initial tests suggest a possibility of Valley Fever, your veterinarian will perform more targeted testing aimed at obtaining a definitive diagnosis. Your veterinarian may begin by testing samples of blood or other bodily fluids for Coccidioides immitis. While these tests can definitively confirm a diagnosis if the organism is found, false negatives are relatively common and may require further testing. 

Your veterinarian may also test your dog for antibodies against Coccidioides immitis. The presence of antibodies only indicates exposure, not active infection. However, this can provide an additional level of support for a diagnosis of Valley Fever. Your veterinarian may collect cell samples from any accessible lesions, for microscopic examination. 

In dogs with neurologic signs of Valley Fever (such as seizures), advanced brain imaging such as a CT scan or MRI may be necessary. 

In many cases, multiple tests are needed to make an educated determination of whether or not a dog’s illness is caused by Valley Fever. This is rarely a condition that can be diagnosed on the basis of a single laboratory test. 

How to Treat Valley Fever in Dogs

Giving dog anti fungal medication

Valley Fever is treated with antifungal medications, which are typically administered on an outpatient basis. The duration of treatment will depend on the severity of your dog’s symptoms and response to therapy. Some cases can be treated with as few as six months of antifungal therapy, while other cases require lifelong antifungal treatment to prevent relapse. 

Some dogs can be completely cured with antifungal agents, while many are merely kept in remission through long-term therapy.

Medications for Valley Fever

There are four antifungal drugs used to treat Valley Fever in Dogs

  • Fluconazole
  • Itraconazole
  • Ketoconazole
  • Amphotericin B

Fluconazole, itraconazole, and ketoconazole are all oral medications, administered once or twice daily. 

Amphotericin B is an injectable medication that must be administered intravenously. Dogs typically visit their veterinary hospital for infusions several times weekly. 

General Cost of Treatment for Valley Fever

The cost of Valley Fever treatment can vary significantly, depending on a number of factors. Primarily disease that is diagnosed early will likely be less expensive to treat than advanced, disseminated Valley Fever. 

Additionally, medication costs are lower for smaller dogs than they are for larger dogs. In general, the medications used to treat Valley Fever in dogs typically cost several hundred dollars per month. 

How to Prevent Valley Fever in Dogs

Dog on leash hiking in the desert

Unfortunately, the only sure-fire way to avoid Valley Fever is to avoid living in or traveling to areas where the fungus is found. 

If you live in an area where Coccidioides immitis is found, however, you can reduce your dog’s risk by limiting their exposure to inhaled dust. Keep dogs primarily indoors and walk them outside on a leash, instead of allowing them to roam loose, dig in the dirt, and sniff in rodent holes. Avoid walking your dogs during periods of high winds, if possible. You can further reduce dust exposure by attempting to keep your lawn covered with grass or groundcover.

Although there is currently no vaccine available for Valley Fever, the University of Arizona is working to develop vaccines for use in both humans and pets. 

Related Conditions

  • Fungal pneumonia
  • Cryptococcosis
  • Blastomycosis
  • Aspergillosis
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