Valley Fever (Coccidioidomycosis) in Dogs

Key takeaways

Valley Fever is an infection by the fungus Coccidioides immitis in dogs. 

  • This species of fungus is commonly found in dusty, dry areas in southwestern USA, Mexico, and parts of central and south America
  • Dogs typically become infected by inhaling fungal spores in contaminated dust
  • In most cases, the infection is limited to the lungs, and presents with cough, fever, and weight loss
  • Symptoms start to appear after 1 to 3 weeks after infection
  • In some cases, the infection travels to other organs, affecting the nervous system, bones and joints, and the eyes
  • Diagnosis includes physical examination, diagnostic imaging, tissue biopsy, and testing for antibodies against the fungus
  • Treatment typically consists of antifungal medications
  • Therapy is often aggressive and can take up to a year
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A closer look: Valley Fever (Coccidioidomycosis) in Dogs

Most dogs who come in contact with infectious Coccidioides immitis spores do not get sick. In symptomatic cases, severity varies depending on whether the infection is limited to the lungs or becomes disseminated, meaning that it travels to other parts of the body. With a limited infection, most dogs fully recover. In cases of disseminated infection, the condition is much more serious. Prompt and aggressive treatment is paramount for a good prognosis. Severe cases presenting with serious symptoms such as difficulty breathing, seizures, or collapse may be life threatening and should be treated as an emergency.

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Risk factors

Valley fever in dogs is common in at-risk areas. Risk factors that might make infection more likely include dust storms, exposure to dense underbrush, and exposure to recently disturbed soil. Areas where coccidioidomycosis is common include the southwestern United States, Mexico, and central and South America. Within the United states, the infection is particularly common in southern California, Arizona, and southwest Texas.

In cases of disseminated infection, other parts of the body become infected, affecting particularly bone and joints, the nervous system, and the eyes.

Possible causes

The main cause of infection is the inhalation of contaminated dust containing the fungus spores.

Main symptoms

Most cases of Coccidioidomycosis are limited to the lungs.

Testing and diagnosis

Valley fever presents with symptoms similar to many other diseases, and requires several diagnostic tests to reach a definitive diagnosis. Routine diagnostic tests include a complete physical evaluation and bloodwork. Diagnostic imaging of the chest, such as MRI and X-rays, is often necessary. The final step is confirming the presence of the fungus through tissue biopsy or blood testing for the presence of specific antibodies against the fungus.

Steps to Recovery

Treatment typically involves the prescription of antifungal medications. Therapy is generally aggressive and may require up to a year of treatment time. During treatment, dogs need to be checked regularly and require routine blood work to monitor for possible complications.

The prognosis varies according to the location and the severity of the infection. Infection that is limited to the lungs generally has a good prognosis, and most dogs fully recover. A disseminated infection has a guarded prognosis due to the risk of serious complications. Relapse of symptoms is common in disseminated infections. If the brain or the heart is involved, the survival rate drops significantly.


Coccidioidomycosis is not directly contagious between animals. Prevention is possible by avoiding dusty, dry environments, especially in at-risk areas.

Is Valley Fever (Coccidioidomycosis) in Dogs common?

Valley fever is common in at-risk areas, and seems to affect dogs more severely than other animals.

Typical Treatment

  • Aggressive antifungal therapy
  • Routine checks

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