• Chronic subcutaneous fungal infection caused byPythium insidiosumin tropical and subtropical areas.
• Cause:Pythium insidiosum.
• Signs: Acute onset of rapidly enlarging ulcerated masses of granulation tissue.
• Diagnosis: history, clinical signs, cytology, histopathology, fungal culture.
• Treatment: surgery, immunotherapy, anti-fungal therapy.
• Prognosis: good - if diagnosis is made early and treatment is immediate.
• See also:
  • Subcutaneous fungal infection:Pythium.
  • Ulcerative, granulomatous lesions:Pythium.

Presenting signs

• Acute onset of rapidly enlarging ulcerated masses of granulation tissue with sinus tracts that discharge a thick serosanguineous fluid         .
• Lesions are severely pruritic. Foul odor is noted when necrosis is present.
• Irregularly shaped yellow-tan, gritty masses called "kunkers" are seen in the sinus tracts. Kunkers are composed of sequestered vessels, eosinophils and Pythium hyphae.
• Lesions are usually circular and vary in size according to the duration of infection.
• Most commonly affected areas include distal extremities     , ventral abdomen and thorax.
• Lymphangitis with edema and osteomyelitis may occur in chronic cases, especially on legs     .

Geographic incidence

• Common in tropical and subtropical regions, particularly in states close to the Gulf of Mexico.

• Reported also in Australia, Brazil, Columbia, Costa Rica, Argentina, Greece, France and Japan.

Age predisposition

• All ages can be affected.

Breed/Species predisposition

• No breed predilection.

Cost considerations

• Expensive:
  • Surgery.
  • Anti-fungal therapy.

Special risks

• Transmission ofPythiumfrom infected horses to humans or other horses has not been reported, but exudate may be a source of zoonotic infection.