Fungal Disease - Sporotrichosis


Sporothrix schenkii is a dimorphic fungus and environmental saprophyte that can be found worldwide. Infection occurs when the organisms are inoculated into tissue through puncture wounds.

Sporotrichosis is uncommon to rare in dogs and cats, with highest incidences reported in hunting dogs and intact male outdoor cats.

Clinical signs


Skin lesions are characterized by multiple non painful, non-pruritic, firm nodules that may ulcerate, drain purulent exudate, and crust over.

Lesions are most commonly found on the head, trunk, or distal extremities. Nodules on the distal limbs may spread up ascending lymphatic vessels to form more ulcerated, draining nodules.

Regional lymph adenomegaly is common. Dissemination is rare.


Skin lesions may include non-healing puncture wounds, abscesses, cellulitis, crusted nodules, ulcerations, purulent draining tracts, and sometimes tissue necrosis.

Lesions usually involve the head, distal limbs, or tail base. Concurrent lethargy, depression, anorexia, and fever may be present. Dissemination is common.

Differential diagnosis

Differentials include other fungal and bacterial infections and neoplasia.


Cytology (exudate, tissue aspirate): suppurative or (pyo)granulomatous inflammation. Intracellular and extracellular round, oval, and cigar-shaped yeasts are usually easy to find in cats but are difficult to find in dogs.

Dermatohistopathology: nodular to diffuse suppurative or (pyo)granulomatous dermatitis. Yeasts that may resemble cryptococcal organisms are easily found in cats but are rarely found in dogs.

Immunofluorescent testing: detection of Sporothrix antigen in tissue or exudates.

Fungal culture: S. schenckii is easy to culture from infected cats but may be difficult to isolate from infected dogs (fungal cultures are highly infectious).

PCR analysis, where available, may simplify the diagnosis.


Long-term (weeks to months) systemic antifungal therapy should be administered and continued at least 1 month beyond complete clinical resolution.

Treatments include the following:

  • » Ketoconazole 5–15 mg/kg PO with food q 12 hours
  • » Fluconazole 10 mg/kg PO with food q 24 hours
  • » Terbinafine 30–40 mg/kg PO q 24 hours
  • » Itraconazole (Sporanox) 5–10 mg/kg PO with food q 12–24 hours
  • » In cats, the drug of choice is itraconazole (Sporanox).

Historic therapies include the following

  • » In dogs, the traditional treatment is supersaturated potassium iodide 40 mg/kg PO with food every 8 hours.
  • » In cats, supersaturated potassium iodide 20 mg/ kg PO with food q 12 hours

Prognosis: is fair to good, but relapses can occur. No cases of disease transmission from dogs to humans have been reported, but infected cats are highly contagious to people. Good hygiene and gloves should be utilized when handling the patient.

Recently Discussed Topics

Blog Archive