Bacteriology and Mycology: Sporotrichosis

Sporotrichosis

SPOROTRICHOSIS

Sporotrichosis is caused by the dimorphic fungus Sporothrix schenckii.
The disease is characterized by nodular lesions that suppurate, ulcerate, drain, and involve the cutaneous and subcutaneous tissues and the adjacent lymphatics.
The fungus is widespread in nature, found in soil, on wood, and on other vegetation.
The organism gains entrance to the skin through wounds or by traumatic implantation.
Occasionally (especially in dogs), the infection may spread to involve bone, muscle, the central nervous system, lungs, or the genitourinary tract.
Infections are common, particularly in horses and dogs. In dogs, the disease is more likely to disseminate and result in a fatal infection.
In horses, the disease must be differentiated from epizootic lymphangitis (caused by Histoplasma farciminosum).
The lymphocutaneous form may be nonsuppurative, or may result in ulcerations and pus that discharge at several sites along the lymphatic channel, which serves as a means of transmission for the organism within the animal.
Laboratory rodents are highly susceptible to experimental infection, indicating the virulence of this organism is greater than that of the opportunistic fungi.
The disease is infectious, but not contagious, and is chronic.
This dimorphic fungus can be isolated from lesions on brain heart infusion agar, blood agar, or Sabouraud agar with cycloheximide and chloramphenicol.
The mold is white when young, then turns brown to black.
The hyphae are septate and fine, and the microconidia form in clusters at the hyphal tips or as sessile forms at the sides of the hyphae.
Differentiation from similar looking fungi is by conversion of the mold to the yeast phase.
Single-celled, cigar-shaped yeasts may or may not be seen in pus from lesions.
Fluorescent antibody enhances visualization and confirmation of the disease.
Serological diagnosis can be made by demonstration of a rise in complement-fixing antibody.
Potassium iodide, Amphotericin B, ketoconazole and micoconazole are effective for treatment.

Last modified: Monday, 4 June 2012, 6:35 AM

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VMC 311: Systematic Veterinary Bacteriology and Mycology (2+1)

Sporotrichosis

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