Recognizing and Diagnosing Valley Fever in Animals

Valley Fever, also known as coccidioidomycosis or simply “Cocci,” is fairly common in animals that live in or travel to the Southwest. The illness occurs after inhaling airborne particles of the coccidioides species fungus, which is found in dirt and dust across Arizona.

Certain animals are more susceptible to Valley Fever than others. It is estimated that somewhere between 6 to 10 percent of dogs that live in Pima, Pinal and Maricopa counties will become sick with Valley Fever in a given year. Llamas, alpacas and small primates are highly susceptible and often develop severe symptoms. Llamas and alpacas in particular are acutely sensitive to Coccidioides spp. and often die as a result of infection

Valley Fever has also been seen in:

  • Cats
  • Horses (although uncommon)
  • Cattle and other livestock
  • Zoo animals, including kangaroos, wallabies, tigers, bears, badgers, otters, etc.
  • Marine mammals, such as sea otters and dolphins
  • Wildlife, including skunks, cougars and javelina

Proper Diagnosis Is Imperative

Fortunately, most animals that contract Valley Fever are asymptomatic and therefore do not require treatment. Others develop respiratory symptoms that require treatment with antifungal medication. Some animals will develop severe forms of the disease that can be deadly without intervention. The best chance animals have at surviving Valley Fever is when they receive a timely diagnosis.

Valley Fever Symptoms

The symptoms associated with early respiratory Valley Fever are similar to other infections:

  • Coughing
  • Fever
  • Weight loss
  • Lack of appetite
  • Lethargy

As the illness progresses, pneumonia might settle in the lungs, which may be visible on X-ray. If the illness goes undetected and/or untreated, it can spread to other parts of the body. In dogs, Valley Fever that spreads beyond the lungs usually affects the legs, causing lameness. Other animals can experience debilitation, too, including marine animals. Other signs of disease dissemination include:

  • Lameness or swelling of limbs
  • Back or neck pain, with or without weakness/paralysis
  • Seizures and other manifestations of brain swelling
  • Soft abscess-like swelling under the skin
  • Swollen lymph nodes 
  • Non-healing skin wounds that ooze fluid
  • Eye inflammation with pain or cloudiness
  • Unexpected heart failure
  • Swollen testicles

Diagnostic Tests for Valley Fever

Valley Fever can be difficult to diagnose. It often requires multiple diagnostic tests, including:

  • A Valley Fever blood test (also called Cocci serology or Cocci titer)
  • General blood tests and blood cell counts
  • Chest X-rays
  • Bone and joint X-rays

Even so, tests given early in the disease process may produce false negatives. Tests may need to be repeated after a period of three to four weeks, or additional tests may need to be required, including:

  • Fluid culture
  • Biopsies or aspirates
  • CT or MRI scans of the brain or spinal cord (for animals experiencing paralysis or seizures)

For more on Valley Fever in animals, visit the Valley Fever Center of Excellence website.