CHAPTER 44 SPOROTRICHOSIS 659
Cats: male-intact outdoor or stray cats innoculated from claws and teeth during fights.
Exposure to soil rich in decaying organic debris; increased prevalence in tropical and
subtropical zones.
Exposure to infected animals or clinically healthy cats sharing a household with an
affected cat.
Immunosuppression is a risk factor for development of disseminated disease.
CAUTION– zoonotic disease: proper precautions should be taken to prevent infec-
tion; a break in the skin is not required for transmission; disease has become endemic
in some areas.CLINICAL FEATURES
Cutaneous form – dogs: multiple firm nodules or plaques that may crust or ulcerate
and drain; typically affecting the head or trunk.
Cutaneous form – cats: multiple ulcerating nodules to lesions that appear initially as
nonhealing wounds or abscesses mimicking wounds associated with fighting; typi-
cally affecting the head, lumbar region, or distal limbs (Figures 44.1–44.3).Cutaneolymphatic form: extension of the cutaneous form through the lymphatics
resulting in the formation of new nodules that frequently ulcerate to form draining
tracts or crusts; lymphadenopathy is common.Disseminated form: systemic signs of malaise and fever.
DIFFERENTIAL DIAGNOSIS
Infectious: bacterial and fungal diseases presenting with nodules and draining tracts
(e.g., cryptococcosis, blastomycosis, feline leprosy, histoplasmosis).
Other causes of granulomatous to pyogranulomatous dermatitis (e.g., foreign body,
panniculitis).
Neoplasia.
Deep bacterial infection.
DIAGNOSTICS
Cytology of exudates: cigar- to round-shaped yeast found intracellularly or free in the
exudate; organisms are generally plentiful in cat lesions but scarce in dogs (Figures
44.4, 44.5).Biopsy: organisms usually numerous, especially in cats; fungal stains (PAS or GMS)
may aid in the diagnosis; the absence of demonstrable organisms in tissues from dogs
does not preclude diagnosis (Figures 44.6, 44.7).Cultures: samples obtained from deep within draining tracts.
CAUTION– zoonotic disease; laboratory personnel must be warned of the potential
differential diagnosis; cultures should not be attempted until other differential diag-
noses have been eliminated.