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938 Sporotrichosis

Sporotrichosis
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• Cats: ≈97% of affected cats have one or
BASIC INFORMATION
multiple skin lesions, commonly on the testing: positive in < 1% and 8% of affected
cats, respectively
Definition distal limbs, tail base, or head (face or nasal • Cytologic exam from aspirates, exudates, or
The mycotic disease is caused by the dimorphic plenum), often with mucosal involvement. skin preps: diagnostic
fungus Sporothrix schenckii, which clinically ○ Draining puncture wounds, abscesses, or ○ Organism is small (3-5 mcm in diameter
manifests with chronic granulomatous skin cellulitis and 5-9 mcm long [slightly smaller than
lesions. Sporothrix brasiliensis is emerging as a ○ Ulcerations, purulent exudate, and large erythrocytes]) and round, oval, or cigar
more pathogenic form in Brazil and neighboring crusted lesions shaped. Large numbers of organisms are
South American countries. ○ ≈44% of affected cats have respiratory found in exudate in cats; small numbers
tract signs are found in dogs.
Epidemiology • Dogs: multinodular truncal or head lesions; • Positive bacterial cultures from secondary
SPECIES, AGE, SEX dermal or subcutaneous infection, often Staphylococcus pseudinterme-
• Cats, dogs, humans, horses, pigs, and ○ Ulcerations with purulent exudate and dius
cattle; young to middle-aged cats and dogs crust formation are possible.
predominate. ○ Lymphocutaneous form: nodules on distal Advanced or Confirmatory Testing
• Rose-grower’s disease in humans limb, ascending through lymphatics, and • Histopathologic exam of nodules: diagnostic
associated lymphadenopathy • Fungal culture: notify laboratory of the
RISK FACTORS possibility of Sporothrix organisms because
• The disease is often acquired by inoculation Etiology and Pathophysiology of the infectious nature of sample to humans
from puncture wounds, and outdoor- • Inoculation of mycelial form of S. schenckii (zoonosis risk). For the same reason, never
roaming dogs are overrepresented. For cats, into tissues leads to production of the yeast culture suspected sporotrichosis lesions in
prevalence is higher among fighting, intact form. house.
males. • Incubation period of ≈1 month • The Centers for Disease Control and Pre-
• A higher concentration of organisms exists in • Pyogranulomatous inflammation occurs, vention, Atlanta, can perform fluorescent
soils rich in decaying organic matter, barberry with organisms seen in macrophages and antibody testing on exudates or tissue.
and rose bush thorns, sphagnum moss, and neutrophils.
tree bark. • Lymphatic dissemination to spleen, liver, TREATMENT
• Immunosuppression allows for dissemination. lung, eyes, bones, central nervous system,
muscles, mammary gland, testis, and Treatment Overview
CONTAGION AND ZOONOSIS epididymis • Antifungal treatment of organisms, with
• Cat-to-cat or cat-to-human transmis- ○ Lung and liver are predominant sites for treatment continuing for 30 days beyond
sion is considered possible, especially to dissemination in cats. apparent cure
immunosuppressed people (by wounds or • Dissemination is rare in dogs but may • Corticosteroids or other immunosuppressives
contaminated claws). occur in up to 50% of cats, especially are contraindicated.
• Dog-to-dog or dog-to-human transmission with immune-suppressive dosages of
is unlikely/rare due to low numbers of corticosteroids. Acute and Chronic Treatment
organisms found in lesions. Dogs: options include one of the following:
DIAGNOSIS • Itraconazole or fluconazole 5-10 mg/kg PO
GEOGRAPHY AND SEASONALITY with food q 12-24h for 30 days beyond
• Worldwide distribution; temperate to tropical Diagnostic Overview apparent cure, or
climates Diagnosis is based on geography, history, and • Supersaturated solution of potassium iodide
• Found in Mississippi and Missouri River physical exam findings, with positive cytologic (SSKI) 40 mg/kg PO with food q 8-12h for
valleys; infrequent in California and south- results. Suspicion is also warranted with skin 30 days beyond apparent cure, or
western United States wounds that are not responding to standard • Ketoconazole 5-15 mg/kg PO with food q
antibiotic therapy. 12h for 30 days beyond apparent cure
Clinical Presentation • Terbinafine 25-30 mg/kg/day for 30 days
DISEASE FORMS/SUBTYPES Differential Diagnosis beyond apparent cure
• Three clinical forms: cutaneous, lymphocu- • Deep cutaneous bacterial infection Cats:
taneous, and multifocal disseminated • L-form bacterial infection • Itraconazole is the treatment of choice for
• Dogs: predominantly cutaneous, • Systemic mycosis cats; better absorption with suspension
lymphocutaneous • Squamous cell carcinoma formula; or 5-10 mg/kg (capsules) PO q
• Cats: all three forms • Immune-mediated disease, systemic lupus 12-24h for 30 days beyond apparent cure
erythematosus, pemphigus, vulgaris, allergy, • Itraconazole 5-10 mg/kg q 12-24h with
HISTORY, CHIEF COMPLAINT drug eruption SSKI (2.5-20 mg/kg/day) may be a better
• Cutaneous lesions (nodular to ulcerated), • Leishmaniasis (dogs) combination for resistant infections in cats.
possibly with draining tracts
• Lethargy Initial Database Possible Complications
• Anorexia • CBC, serum biochemistry profile, urinalysis: • SSKI can cause systemic iodination (ocular
anemia, leukocytosis with neutrophilia, and nasal discharge, dry haircoat with scaling,
PHYSICAL EXAM FINDINGS hypoalbuminemia, and hyperglobulinemia vomiting, depression, collapse). If signs are
• Fever: suggests possible disseminated disease commonly observed mild, discontinue the medication for 1 week
and immunocompromised state • Feline leukemia virus (FeLV) and feline and reinitiate; if signs are severe, change to
• Depression immunodeficiency virus (FIV) serologic different therapy.

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