A pathogenic fungus called Coccidioides immitis causes Valley Fever in both dogs and humans. The fungus is found in dry, arid soil more common in the Mexico, Southern United States and parts of Central America. When dust is raised from that soil, the fungus is inhaled. Dogs who have been around construction areas, who dig frequently, or are out in the wind, are especially susceptible. Young dogs or dogs with weakened immune systems are also more likely to develop Valley Fever. The fungal infection is called Coccidioidomycosis. It can cause mild to to extreme respiratory infections. The mild form of disease is more common and can be easily treated; the more severe form of the disease can be life threatening.
If infection happens, the inhaled spores burst in the lungs and start growing, usually in the lymph nodes. If the immune system does not kill the fungal organism here, they spread to many parts of the body, involving bone and eye tissue. Hunting dogs are particularly at risk of being exposed to the fungal spores, but even indoor dogs have a chance of exposure following a dust storm when billions of spores become airborne. A few years ago after a severe earthquake in the Los Angeles area disturbed dust, sand, and old buildings, several dogs were reported as having contacted the disease. However, the months of greatest exposure to the spores are May through August, when the fungi stop growing and produce spores to survive the dry, hot summer.
Symptoms of Coccidioidomycosis
Symptoms include: pneumonia-like symptoms, lack of apetite, lethargy, seizures and a harsh cough. In severe cases, the infection can spread throughout the dog’s body creating additional symptoms. Secondary symptoms may include: skin lesions, swollen lymph nodes and lameness. The illness can be chronic and untreated animals will die.
The lymph nodes may be swollen and enlarged along with extreme pain and lameness as the disease involves the bones or spinal column, and enlarged joints. Since it takes several months for these signs to become apparent, diagnosis is often delayed until the disease has progressed to the point where the dog is very ill.
Diagnosis of Coccidioidomycosis
Most diagnosis of Valley Fever is based on a history of travel in prevalent areas, clinical signs, and laboratory testing. This fungus is difficult to diagnoses and is sometimes mistaken for other fungal diseases, cancer, pneumonia, cancer, or Lyme disease. If your vet suspects Valley Fever, blood tests, x-rays, or antibody testing may be used to help diagnose the disease. Blood testing to identify circulating antibodies to Coccidioides is often used as a presumptive test if a diagnosis can not be made through biopsy or a sample from a draining lesion.
Treatment of Coccidioidomycosis
Long-term oral antifungal medications like ketoconazole, given twice a daily, is the usual treatment. The treatment may last a year in severe cases. Itraconazole may also be prescribed. It is more expensive but encouraging results have been reported. When cases a not severe they can be successful. With severe cases the prognosis is usually poor but with aggressive long-term treatment some dogs have pulled through.
It is not spread from one animal to another; it is not highly contagious; and can not spread from animal to man.
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