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Sporotrichosis |
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- Subcutaneous infection by Sporothrix schenckii. Organism is dimorphic, grows as mold in soil and as yeast in skin.
- Distribution - worldwide, prevalence varies. Grows as a saprophyte in moss, soil.
- Causes nodular lesions in cutaneous and subcutaneous tissue; swollen lymph nodes.
- Horses - characteristic nodular lesions
- Dogs - can disseminate
- Cats - seem more susceptible, disease tends to cause severe ulcerative lesions, dissemination. Zoonotic threat to humans.
- Humans - nodular lesions, often follows cut or puncture wound (e.g. gardeners).
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Pathogenesis |
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- Organism resides in soil, is implanted in skin by puncture wound or cut.
- Yeast multiply locally, evade phagocytes.
- Yeast enter draining lymphatics, multiply in draining lymph node. This enlarges, ulcerates.
- Infection progresses along draining lymph nodes.
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Treatment |
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- Usually responds to KI, either orally or i.v.
- Mechanism of action unknown.
- Iodide toxicity (indigestion, lacrimation, cardiac irregularities) common but reversible.
- Amphotericin B and ketoconazole also appear to be effective.
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Diagnosis |
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Histopathology
- Look for cigar-shaped yeast, often rare except in cats.
- Fluorescent Ab available for diagnosis.
- "Asteroid bodies" , flattened central yeast surrounded by leukocytes
- Can isolate on Sabouraud’s and other media - grows as mold greater than 28 C, yeast at higher temp
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Immune response |
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- Protective immunity not well understood.
- Experimental studies suggest CMI is important.
- There are serologic tests for Ab response. Abs not thought to contribute to protection.
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