Besides the types of fungi that attack the skin and cause ringworm or dermatophytosis, there are several which enter the body and cause internal illness. Most of these fungi grow in the soil and are not infectious, but when they die, they produce spores, which are able to enter the cat and cause infection. Most fungi thrive in a particular region of the country so cats that moved from one area of the country to another might have little resistance to fungi native to other regions. In general, cats rarely become infected by these organisms.
Cryptococcosis is a fungal organism that most commonly affects the respiratory system, mainly the nose and is the most common systemic fungal infection in cats. The fungus seems to grow best in rich, organic soils and pigeon droppings anywhere in the United States. When the fungus dries it can become aerosolized and inhaled thus leading to infection. The organism initially will grow within the nasal cavity and sinuses but later spread to attack the eyes, brain and spinal cord, skin and lungs. Many cats with the infection will be FeLV and/or FIV positive as well.
Clinical signs will include a nasal discharge which can be thick and sometimes contain blood, sneezing, swelling to the nose/face area, fever, lymph node enlargement, blindness, anterior uveitis, seizures, staggering, behavioral changes and other symptoms depending as to where the fungus has spread within the body. Diagnosis is based on history, physical findings, blood counts, serum chemistry, cytology, X-rays, CSF analysis, serology and fungal culture. Other upper respiratory diseases can mimic cryptococcosis so an exact diagnosis is quite important to insure proper treatment.
Histoplasmosis is a systemic fungal disease caused by the fungus Histoplasma capsulatum. It is the second most common systemic fungal disease of cats. The organism grows in soils rich in bird or bat feces in the Ohio and Mississippi River valleys. Inhalation of a portion of the fungus known as a "Microconidia" will cause the disease, but it is also thought that some form of ingestion may produce the gastrointestinal version of the illness. This particular fungus, while inside the body, grows inside host cells and attacks primarily the respiratory and digestive systems. ((Area of Histoplasmosis))
Clinical signs of the respiratory form of the disease include a non-productive cough, trouble breathing, fever, weight loss, lethargy and poor appetite. Gastrointestinal signs include chronic diarrhea and weight loss. Many cases may be subclinical, meaning that the symptoms are not seen and the cat gets better without treatment. Rarely, the fungus will spread and attack other organs causing hepatitis, lymph node enlargement, neurologic disease, lameness or infections of the eye. ((Fungal Pneumonia))
Diagnosis is based on these clinical signs, physical examination, a suspicion of exposure, X-rays, blood counts and serum chemistry analysis, biopsy of lesions, or special serological tests for the fungus. Cats often have advanced disease when diagnosed and their hope of being cured is only fair in such cases. Treatment
Aspergillus is a common fungus of which there are many varieties in our environment. It usually causes disease in animals otherwise weakened or with poor general immunity. Because these fungi are so common, most cats inhale some of their spores on a daily basis, but again, very rarely will cats become infected. Cats that do become infected are likely to have FeLV, FIV or feline panleukopenia. Clinical signs would include coughing, difficulty breathing, vomiting, diarrhea and weight loss. Diagnosis is based on clinical signs, cultures and cytologic examination of nasal exudates and biopsy of affected tissues. Treatment
COCCIDIOMYCOSIS (VALLEY FEVER)
Coccidiomycosis is a systemic fungal disease caused by the fungus Coccidiodes immitis. This organism grows in the desert soils of southern California, Arizona, New Mexico, Texas and Northern Mexico. The fungi grows readily during cool, wet times of the year; during the drier seasons it produces infective spores which can be inhaled from the dust in the air. The infection, however, cannot transmit between infected cats or from cat to man. It is important to note that while many cats will be exposed to the spores of the organism, only a few rare cases have been reported.
Clinical signs would depend on where the fungus is growing inside the body. Several forms of the disease are recognized: a cutaneous form, where firm, ulcerated but painless nodules form in the skin and local enlargement of lymph nodes is also often seen; a respiratory form, presenting as a persistent hacking dry cough; and the most serious form, disseminated disease, which may start as a cough and trouble swallowing, eventually attacking the bones and internal organs which may lead to lameness, joint pain in one or multiple joints, weight loss, fever and weakness. Enlargement of multiple lymph nodes may also been noted. Rare cases of anterior uveitis have also been reported. Diagnosis is based on history and physical examination, X-rays of the chest, serology for valley fever, blood counts and occasionally biopsies of bone, lumps or other organs. Treatment ((Area of Coccidiomycosis))
Blastomycosis is a very uncommon systemic fungal disease of cats caused by the organism Blastomyces dermatitidis that grows in the soils of the Great Lakes region, Ohio, and Mississippi River valleys. Cats are infected by inhalation of fungal spores and initially show symptoms of respiratory disease. ((Area of Blastomycosis)) ((Fungal Pneumonia))
Clinical signs include various degrees of coughing and/or trouble breathing, fever, weight loss, poor appetite, lethargy and lymph node enlargement. In some cases, the disease spreads from the respiratory system and may cause tearing and redness to the eye or a more serious condition called uveitis, with some cats becoming blind. A few patients will develop open ulcerated sores, bone infections and neurologic infections. Diagnosis is based on these clinical signs, probability of exposure, blood counts, X-rays, cytologic evaluation of lesions or exudates, biopsy and special serological tests for the fungus. Treatment
OF SYSTEMIC FUNGAL DISEASE. All systemic fungal diseases seem to respond well to several related oral medications: iatraconazole, fluconazole, or, ketoconazole. Fluconazole is most effective and well tolerated by cats in general. Most patients will need treatment for several months, with some disseminated cases needing treatment for up to a year. A few cats may prove incurable, but it is impossible to identify these patients ahead of time; it is a wait and see proposition. Regular blood tests to monitor the success of the treatment as well as watching for liver or other organ dysfunction, which is rare, is very important.
Another drug available for the treatment of these diseases is amphotericin B, which can be very effective in killing the fungus, but is quite toxic to the patient, and must be administered in the hospital while the cat is on IV fluids to flush the kidneys, and (hopefully) prevent kidney failure. Hospitalization and careful monitoring for several days will also be needed, and if no toxic effects are encountered, good results are possible. This drug is probably best reserved for severe cases or cats with neurologic involvement.
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©2007 James W. Day D.V.M., P.C.
