59 (149)

5 : Deep mycoses

Treatment

Orał itraconazole (10 mg/kg SID or BID), given for at least two months beyond clinical resolution, is necessary. For serious systemie forms, itraconazole can initially be given in association with intravenous amphotericin B (0.25-0.5 mg/kg, three times weekly) until a combined dose of 4-8 mg/kg has been reached. Amphotericin B must not be given if the patient has an associated renal insufficiency. Orał fluconazole (2.5-5 mg/kg SID or BID) is an altemative therapy when there is ocular and neurological involvement. Treatment must be continued for at least two months beyond clinical resolution. Response to treatment is usually good when there are pulmonary signs.

Blastomycosis

Aetiopathogenesis

Blastomycosis is a systemie mycosis caused by the saprophytic dimorphic fungus, Blastomyces dermatidis. The infective mycelial form of Blastomyces dermatidis lives in sandy, acid soils close to water. The disease is endemic in the Mississippi, the Missouri and Ohio valleys and in some parts of western North America^l9. Blastomycosis has not been reported in cats in Europę. Abyssinian and Havana cats appear predisposed.

Infective forms enter the host via the respiratory tract and transform into yeasts in pulmonary tissue where they provoke initial lesions. The disease can then be spread via the lymphatics and blood into other organs including the skin. Involvement of lymph nodes, kidneys, gastrointestinal tract, eyes, nervous system and skin has been reported. Cats seem to have natural resistance to the disease.

Clinical features

Signs vary according to the organ affected. Systemie signs (depression, weight loss, respiratory, neurological and ocular signs) are common. Dermatological lesions present as multiple uleerated nodules.

Diagnosis

Diagnosis is based on the history, systemie (respiratory, neurological and ocular) and sometimes dermatological signs, cytology, histopathology and fungal culture.

Cytological and histopathological examination of deep samples does not always allow identification of Blastomyces dermatidis as these fungal organisms vary in number in lymph nodes, lungs and skin. Special stains (e.g. Gomori, PAS) help to demonstrate the organism within smali pyogranulomas, surrounded by epithelioid macrophages and multinucleate giant cells. Blastomyces dermatidis appears as a round or oval yeast, 5-20 urn in diameter, usually extracellular and often with broad-based budding. Immunofluorescent techniąues are sometimes necessary when using histopathological examination to identify fungi. It is characterised by a thick, refractile, double-contoured celi membranę. Confirmation of the diagnosis is madę easier by the use of immunological techniąues on tissue sections.

Fungal culture can be used to isolate and identify Blastomyces dermatidis which grows as a yeast on blood agar at 37°C and in mycelial form on Sabouraud’s agar at 25 °C. Mycelial forms represent a serious source of potential infection for people, a fact which always justifies using specialist laboratories in case of suspicion.

Serology (ELISA) testing is currently being evaluated and may in the futurę be useful for confirming the diagnosis of blastomycosis in the cat.

A moderate non-regenerative anaemia and hyperglobulinaemia are often seen in systemie forms. Treatment

Orał itraconazole (5 mg/kg SID or BID), given for at least two months beyond clinical resolution, is necessary. For serious systemie forms, itraconazole can initially be given in association with intravenous amphotericin B (0.25-0.5 mg/kg, three times weekly) until a combined dose of 4-8 mg/kg has been reached. Amphotericin B must not be given if the patient has an associated renal insufficiency. Orał fluconazole (2.5-5 mg/kg SID or BID) is an altemative therapy when there is ocular and neurological involvement. Treatment must be continued for at least two months beyond clinical resolution. The prognosis is generally good except when neurological and severe pulmonary forms are present.

5.9