Sporotrichosis

Sporotrichosis in a horse -Copyright Professor Andrew N. Rycroft, BSc, PHD, C. Biol.F.I.Biol., FRCPath

Sporotrichosis cigar shaped cells -Copyright Professor Andrew N. Rycroft, BSc, PHD, C. Biol.F.I.Biol., FRCPath

• Sporothrix schenckii

• Occurs in soil, wood and vegetation
  • Saprophyte of both decaying and healthy vegetation

• Worldwide

• Exogenous infections through wounds

• Sporadic infections

• Non-contageous

• Causes subcutaneous nodules or granulomas
  • Nodules ulcerate discharging pus

• Spread via the lymphatics

• The bones and viscera can be involved which terminates in mortality
  • This is rare
  • Reported in dogs and horses

• Affects dogs, horses, cats, monkeys, mules, camels, donkeys, cattle, fowl and rodents
  • Most commonly seen in horses as an ascending lymphocutaneous infection of the legs
  • Can be confused with epizootic lymphangitis in horses

• Single cell, cigar shaped
  • Usually found within neutrophils
  • Yeast cell clusters with peripheral eosinophilic rays can be seen in tissue sections

• Stained using PAS, Gram stain (positive), fluorescent antibody and Calcofluor White

• Latex agglutination and immunodiffusion serology can be performed

• Grows on Blood agar and Sabouraud's Dextrose agar in one to three weeks
  • At 37°C:
    • Colonies are smooth, cream to tan coloured and soft
    • No mycelium can be seen
  • At 25°C to 27°C:
    • Colonies turn from white and soft to tan to brown to black
    • Leathery, wrinkled and coarse
    • Mycelium can be seen as branching septate hyphae
    • Conidiospores can also be seen

• Potassium iodide treatment orally
  • 5-fluorocytosine and amphotericin B can also be used