• Prolonged contact with lake, pond, swamp, or flood water

• Minor wounds

• Pythiosis occurs in tropical and subtropical areas, including Australia, Brazil, Costa Rica, India, and Thailand. In the United States, pythiosis occurs in states along the Gulf of Mexico.

• Most cases occur during warmer and wetter months of the year, especially the summer.

• P. insidiosum generally infects the wounds in the distal portions of the body, including the limbs below the carpus and hock, ventral abdomen (Figure 1), and ventral thorax (areas more likely to be in contact with stagnant water), as well as the lips, nostrils, face, external genitalia, neck, and trunk.

Cutaneous granulomas may involve or spread to the muzzle and lips.

Lesions are usually single and large nodular eroded to ulcerative granulomas associated with moderate to severe pruritus and oozing of serosanguineous discharge (Figure 2).

Severe pruritus, which often leads to self-mutilation

If excised, tissue has a thickened fibrotic dermis (pink) and contains scattered areas of red surrounding a yellow-tan, gritty, central necrotic core (“leeches” or “kunkers”). Kunkers range from 2 to 10 mm, which is larger than those seen with zygomycosis.

Malodorous (associated with tissue necrosis)

Lesions involving the limbs are accompanied by lymphangitis with severe edema or swelling (Figure 3)

The infection is locally invasive (spreading from the subcutaneous to lymphatics and deeper tissues (eg, bones, tendon sheaths, joints).

Osseous involvement generally occurs in chronic lesions (>2 months’ duration).

Metastasis (spreading to lungs) may occur (Figure 4).

Gastrointestinal lesions may occur.

• Lesions are often heavily contaminated by bacteria (especially gram-negative organisms).