Page 284 - Cote clinical veterinary advisor dogs and cats 4th

122 Blastomycosis

• Agar gel immunodiffusion test: a positive treatment and stop if > 50% increase in • Animals with severe lung involvement
test result is very specific, but the test is • Lipid-complexed amphotericin B (dyspnea) or CNS involvement have a guarded
either parameter.
VetBooks.ir (p. 1314). ○ Dogs, cats: 1-2 mg/kg IV 3 times weekly. • More than 1500 bands/microL on CBC may
prognosis. Most deaths occur in the first week
not sensitive early in the disease process
after presentation, despite treatment.
Higher cumulative doses can be achieved
be a poor prognostic indicator.
TREATMENT
because less nephrotoxic.
• Recurrence of blastomycosis occurs in
Treatment Overview Drug Interactions 20%-25% of treated dogs in a few months
Itraconazole is considered the treatment of Itraconazole should not be administered with to a year after completion of treatment. Most
choice, but fluconazole may be more cost- drugs that inhibit cytochrome P450, such as dogs with recurrence are cured when given
effective despite longer treatment duration. some anticoagulants. another course of treatment.
Dogs with neurologic disease should be treated • Eyes that have anterior uveitis usually become
with amphotericin B. Possible Complications glaucomatous and blind. Retinal lesions are
• Itraconazole may cause hepatotoxicosis and more likely to be cured. Blind eyes should
Acute and Chronic Treatment anorexia in dogs and cats. Itraconazole at be enucleated because they can harbor
• General supportive care to include supple- doses of 10 mg/kg/d may produce vasculitis, organisms.
mental oxygen (p. 1146) to dyspneic patients. with ulcerative skin lesions that may resemble
Dyspnea is considered a negative prognostic lesions of blastomycosis. PEARLS & CONSIDERATIONS
factor. • Nephrotoxicity with amphotericin B
○ Dogs with dyspnea may require short-term • Lung disease often worsens initially with Comments
glucocorticoid therapy (predniso[lo]ne treatment due to inflammation from dying • Early recognition is critical for successful
0.5 mg/kg q 12h × 5-7 days) to reduce organisms. Glucocorticoid therapy can be treatment. Comprehensive diagnostic testing
pulmonary inflammation. Glucocorticoids lifesaving in dyspneic dogs but should be should be done initially in suspect cases.
should not be used before antifungal given only after starting antifungal drugs. • Obtaining a travel history when dogs have
therapy is begun. signs suspicious of blastomycosis is an
• Antifungal drugs Recommended Monitoring important step for raising or lowering the
○ Itraconazole is considered the drug of • Liver enzyme activities should be monitored disease on the differential diagnosis.
choice in most cases. every 2-4 weeks during treatment in animals
○ Fluconazole, although requiring longer treated with itraconazole and measured if Prevention
treatment times, is usually more cost- the patient develops anorexia. Restrict activity in endemic areas, particularly
effective in dogs. • Perform thoracic radiographs monthly to lakes, creeks, and heavily shaded areas with
○ Amphotericin B may be superior in severe assess response to treatment in dogs with moist soil in endemic areas.
disease and in dogs with neurologic pulmonary involvement. Median time to
involvement. resolution of radiographic signs ≈6 months. Technician Tips
• Itraconazole Improvement typically continues even after • Although the disease is infectious (acquired
○ Dogs: 5 mg/kg q 12h PO for 3 days, then discontinuing treatment. by inhalation), it is not transmitted by
5 mg/kg PO q 24h for at least 60 days • Following urine antigen concentrations is inhalation from an infected patient to other
and for 30 days after all evidence of disease useful in predicting when treatment can be animals or humans. Most zoonotic infections
has resolved. Give capsules with canned discontinued and for documenting relapse. are acquired by needlestick injuries after
food for maximal absorption. Brand-name fine-needle aspiration (FNA). Care should
itraconazole is preferred, but generic PROGNOSIS & OUTCOME be taken when handling needles. Specifically,
itraconazole can be effective; poor absorp- needles should not be recapped after FNA.
tion can occur with compounded itra- • The mortality rate is ≈20%. • Never culture a lesion or exudate if it could
conazole. Itraconazole is expensive in large • 50%-75% of dogs can be cured with the harbor Blastomyces; the spores aerosolize from
dogs. initial course of treatment. culture medium and are highly infectious.
○ Cats: 5 mg/kg PO q 12h. The pellets from
the capsules can be mixed with palatable
food for ease of administration. Oral liquid
formulation is available (10 mg/mL) and
has higher bioavailability.
• Fluconazole
○ Dogs: 10 mg/kg PO q 24h for a minimum
of 4-6 months
○ Cats: 50 mg/CAT PO q 24h
• Amphotericin B (IV)
○ Dogs: 0.5 mg/kg IV in 5% dextrose 3
times/week at evenly spaced intervals. A
cumulative dose of amphotericin B of at
least 9 mg/kg is usually required. Therapy
is continued until signs have resolved or
until nephrotoxicity occurs, at which time
treatment can be changed to itraconazole.
○ Cats: 0.25 mg/kg IV 3 times/week.
Monitor closely for nephrotoxicosis.
○ Nephrotoxicity is the main side effect.
Ensure animals are adequately hydrated BLASTOMYCOSIS Cytologic evaluation of a fine-needle aspiration from a patient with blastomycosis. The
before infusion. Monitor blood urea cytologic diagnosis is made based on the thick-walled, basophilic, spherical B. dermatitidis (arrows). The intense
nitrogen (BUN) and creatinine during inflammatory infiltrate surrounding the yeasts is typical.

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