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. When they die, however, they produce spores, which are able to enter the dog and cause infection. Most fungi thrive in a particular region of the country so dogs that moved from one area of the country to another might have little resistance to fungi native to other regions.

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 dogs or from dog to man. It is important to note that while many dogs will be exposed to the spores of the organism, very few will actually become infected with most pets native to an area having a natural level of immunity.

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 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 can cause 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 neurologic disease will occasionally be seen. Diagnosis is based on history and physical examination, X-rays of the chest, a special valley fever test, blood counts and occasionally biopsies of bone, lumps or other organs. Treatment  ((Coccidiomycosis Area Map))  ((Valley Fever Xray))

Blastomycosis is a systemic fungal disease caused by the organism Blastomyces dermatitidis that grows in the soils of the Great Lakes region, Ohio, and Mississippi River valleys. Dogs are 10 times less resistant to this condition than is man and serve as something of a warning system for an outbreak of the disease. Man and dogs are infected by inhalation of fungal spores and initially show symptoms of respiratory disease.

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 dogs becoming blind. Other patients will develop open ulcerated sores, bone infections and reproductive tract 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 ((Blastomycosis Area Map))

Histoplasmosis is a systemic fungal disease caused by the fungus Histoplasma capsulatum. 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. This particular fungus, while inside the body, grows inside host cells and attacks primarily the respiratory and digestive systems.

Clinical signs of the respiratory form of the disease include a non-productive cough, an inability to exercise, 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 dog 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. 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. Treatment ((Histoplasmosis Area Map))

Cryptococcosis is a fungal organism that most commonly affects the respiratory system, mainly the nose and is more common in cats than in dogs. The fungus seems to grow best in pigeon droppings anywhere in the United States. Dogs with chronic nasal infections should be suspect for the condition. Diagnosis is based on clinical signs, culture or cytologic examination of exudates, and special serologic testing specific for the fungus. 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 dogs inhale some of their spores on a daily basis, but again, very few animals will ever become infected. Clinical signs would include a chronic nasal discharge that is thick and pus-like, which may become bloody with time. In very rare instances, the fungus may spread from the nasal cavity and attack the brain or other organs. Diagnosis is based on clinical signs, cultures and cytologic examination of nasal exudates, and on occasion, biopsy of affected tissues. Treatment

TREATMENT OF SYSTEMIC FUNGAL DISEASE. All systemic fungal diseases seem to respond well to several related oral medications: iatraconazole, fluconazole, or the most commonly used, ketoconazole. Most patients will need treatment for several months, with some disseminated cases needing treatment for up to a year. A few dogs 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 dog 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.

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©2007 James W. Day D.V.M., P.C.