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Sporotrichosis is a disease of animals and people caused by the fungus
Sporothrix schenckii. The organism is found worldwide in soils
that are rich in decaying plant matter. Infection is usually caused
by traumatic inoculation of tissues with material contaminated with
the fungus. In people the disease is commonly seen in gardeners,
forestry workers and other occupations associated with the soil. In
cats, sporotrichosis is most commonly identified in outdoor cats. The
portal of entry is typically a skin wound, such as a scratch or bite.
After the
organism enters the tissues, it converts into a yeast-like form and
can present in three clinical forms. It can proliferate locally and
produce lesions at the inoculation site (cutaneous form), it can
spread up regional lymphatics (cutaneolyphatic form), or it can
disseminate systemically (systemic form). It is likely that the
clinical form reflects the host’s immune response and
affected cats should
be tested for feline immunodeficiency virus and feline leukemia virus.
Skin lesions
usually occur at sites that are commonly exposed during cat fights
such as the distal aspects of the limbs, head or tail-base regions.
The lesions may initially resemble the draining puncture wounds of a
fight or ulcerated nodules; however extensive necrosis can occur.
With grooming, cats may spread fungal organisms over the entire skin
surface. The disease can become generalized and cause lung,
kidney, digestive, and central nervous system lesions.
Sporotrichosis is suspected when a cat has an
ulcerative skin lesion that is nonresponsive to appropriate antibiotic
treatment. Cytological and histopathological examination of deep
samples and fungal culture are the most useful diagnostic tests and
special stains may be required to differentiate
Sporothrix from other fungal
organisms. Oral itraconazole (5mg/kg twice daily) is the drug of
choice for this disease. Treatment usually extends 1 month beyond
clinical resolution of lesions/symptoms. Antibiotics are also used
when there is secondary bacterial infection.
Public Health Risks
Feline
sporotrichosis is contagious to humans. People can become infected
following a bite or scratch from an affected cat, or by direct contact
with infected tissues. The most common form in people is the cutaneolymphatic form. Systemic disease in people is rare but has
been observed in immunocompromised patients. People should consult
their physicians for additional information.
Disposable gloves
should be worn when handling a cat suspected of having sporotrichosis
and hands and arms washed well after removing gloves.
By: Sarah Peakheart, DVM
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