Introduction

Histoplasmosis is a serious, potentially fatal disease that can develop in dogs exposed to the causative fungal organism, Histoplasma capsulatum. Fortunately, once the disease is diagnosed, it usually can be treated, although successful treatment takes many months. The therapeutic goal is to clear the infection and thereby relieve the affected dog of all symptoms of the disease.

Treatment Options

Mild cases of canine histoplasmosis typically are treated with a class of anti-fungal pharmaceuticals called “azoles.” The duration of treatment and the selection of the appropriate drugs must be determined by a veterinarian, because treatment choices may differ in cases of mild, moderate and severe disease. Current azole medications that are effective against H. capsulatum include itraconazole, ketoconazole and fluconazole. In mild cases, anti-fungal drugs are administered orally, once or twice a day, for 4 to 6 months. In severe cases, when hospitalization is appropriate, intravenous anti-fungal medications (such as amphotericin B) may be administered in addition to an oral azole drug, oxygen, intravenous fluids and nutritional support.

Anti-fungal drugs can cause a number of adverse gastrointestinal side effects and normally are recommended to be given with a meal. They also are quite expensive, especially if the patient is a large or giant-breed dog. Amphotericin B carries a fairly high risk of causing or contributing to progressive kidney damage. Dogs with histoplasmosis should remain on a high-quality, palatable diet, with free access to fresh water at all times. Regular visits to the veterinarian for assessment of the patient’s progress are also very important to a successful recovery.

Prognosis

The prognosis for dogs with histoplasmosis can range from good to guarded, depending upon how far the disease has progressed at the time it is diagnosed. Once the fungi has disseminated widely throughout a dog’s body, the chances of successful treatment and recovery are significantly diminished.