Fungal Diseases In Cats : Part 2

HISTOPLASMOSIS

This disease is caused by a fungus found in the central United States near the Great Lakes, the Appalachian Mountains, Texas, and the valleys of the Mississippi, Ohio, and St. Lawrence Rivers. In these areas, the nitrogen-rich soil facilitates growth of the causative fungus (Histoplasma capsulatum).

In the majority of cats, histoplasmosis is an insidious disease with fever, loss of appetite, weakness, weight loss, and debilitation. The liver, respiratory system, eyes, and skin may be involved. Lameness may be noted. 

Cats who hunt are at risk for this problem, but cases have been documented where spores blew in a window from pigeon nests on a building. Diagnosis is made by fungal culture, needle aspirate, or tissue biopsy. 

Treatment:

Successful treatment with antifungal drugs, such as itraconazole, depends on early diagnosis. Despite treatment, most cats die from this infection. Mild respiratory cases have the best prognosis. 

SPOROTRICHOSIS

This uncommon skin infection is caused by fungus spores in the soil. These spores usually gain access through a break in the skin. Other routes of infection are by ingesting or inhaling spores. The disease is most common among male cats who prowl in thorny underbrush or sharp prairie grass. Most cases are reported in the northern and central portions of the United States, along river valleys and in coastal areas.

A nodule forms at the site of a skin wound, usually on the feet or legs, the face, or the base of the tail. The hair over the nodule falls out, leaving a moist, ulcerated surface. In some cases there is little surface reaction, but you may see several small firm nodules beneath the skin that appear to form a chain.

On rare occasions, the disease spreads internally to the liver and lungs. In these individuals the outlook for a cure is guarded. The diagnosis is made by removing a piece of tissue and examining it under a microscope, or more conclusively, by growing the fungus in culture. Fungal elements may also be noted in the exudates from wounds.

Treatment:

The response to treatment is excellent when disease is limited to the skin and surrounding tissues. Potassium iodide was the agent of choice and is given orally. Cats must be carefully observed for any signs of iodide toxicity, however, such as vomiting, depression, twitching, and cardiac problems. Itraconazole is one of the newer antifungal drugs and is currently recommended. Amphotericin B is used to treat an internal infection, but only as a last resort. These drugs have toxic potential and require close veterinary management. 

ASPERGILLOSIS

This fungus is found in decaying vegetation and organic-rich soils. Aspergillosis has usually been reported in immunodeficient cats with concurrent feline panleukopenia. Nasal infection similar to that of cryptococcosis and systemic involvement like that of histoplasmosis have been described. Cats may show both pulmonary and intestinal signs.

Nasal discharge may show organisms. The nose may be quite painful and ulcerated. X-rays often show destruction of the bones and sinuses. Blood tests can help in diagnosis, including agar gel immunodiffusion (AGID) and ELISA tests. 

Treatment:

Early detection and treatment greatly increase the odds of success. Opening up the sinuses to provide direct topical treatment is the most successful treatment. Enilconazole has been used for treatment (even applied topically, much gets absorbed systemically), and the drug clotrimazole, which has been used in dogs, may work as well. Itraconazole can be tried.  

BLASTOMYCOSIS

This disease is found along the Eastern seaboard, Great Lakes region, and Mississippi, Ohio, and St. Lawrence River valleys. The fungus has been isolated from cedar trees and pigeon droppings. Cats are more resistant to blastomycosis than are dogs and humans. 

Most cases of blastomycosis in cats involve the respiratory system, skin, eyes, and brain. Respiratory signs are the most common and may involve coughing and labored breathing. Skin lesions in cats may involve large abscesses. The nose, face, and nail beds are common sites of such lesions. Nervous system involvement is not common in cats.

Diagnosis is established by biopsy of infected tissue or culture of infected drainage. Organisms may be identified in discharges. A variety of serologic tests are available.

Treatment:

Itraconazole is the preferred medication and may be needed for as long as two months.