Fungal Infections in Dogs: Histoplasmosis

Histoplasmosis is caused by breathing in Histoplasma capsulatum, which is carried in dust. The fungus causes a variety of respiratory and intestinal symptoms. Some animals recover from the infection without any therapy and others require treatment with antifungal medication that is usually successful. Histoplasma prefers areas that are moist and humid and grows best in soils that contain nitrogen-rich organic matter such as bird or bat droppings. It has been identified in the soil of 31 states in the U.S. Most infections occur in the region of the Ohio, Missouri, and Mississippi rivers.

Dogs and cats can both be infected. Infections are more common in outside dogs and cats, particularly in hunting dogs.

Symptoms of Histoplasmosis

Symptoms are varied and may include labored breathing with increased lung sounds is present, cough, fever and enlarged liver or other organs. Other common symptoms in the dog or cat are weight loss, loss of appetite, and depression.  In dogs with the GI form, diarrhea and blood in the stool are often common symptoms. In addition to these symptoms, both cats and dogs may be anemic and have pale gums.

Diagnosis of Histoplasmosis

Diagnosis of histoplasmosis is often made from information obtained from the history, symptoms, x-rays of the chest and abdomen, and by finding the organisms in the infected tissue. A needle aspirate or biopsy of the infected lymph nodes and lungs can often yield some of the small budding fungal organisms. Presence of the fungus may also be determined by rectal scrapings in dogs with diarrhea.

Treatment of Histoplasmosis

The more acute and widespread the infection is, the less promising is any drug therapy, but with early diagnosis, antifungal drug therapy with itraconazole, fluconazole or ketoconazole the outlook improves. Since Histoplasmosis is primarily a chronic diarrhea disease, the illness can progress so rapidly that not even the antifungal drug can help if treatment and diagnosis is delayed. For severe cases, concurrent treatment with amphotericin has been used with success. The success in treating histoplasmosis is very good if the correct treatment is used and instituted before the animal becomes too debilitated.

Canine histoplasmosis is  not contagious to humans or other animals.
Related articles include:

Moldy Dogs: Fungal and Yeast Infections in Dogs

Fungal Infections in Dogs: Aspergillosis

Fungal Infections in Dogs: Ringworm

Fungal Infections in Dogs: Blastomycosis

Fungal Infections in Dogs: Cryptococcosis

Fungal Infections in Dogs: Coccidioides immitis/Valley Fever

Fungal Infections in Dogs: Pythiosis

Fungal Infections in Dogs: Sporotrichosis

Fungal Infections in Dogs: Zygomycosis

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