Aspergillus and Candida are the most common secondary fungal infections, causing chronic diarrhea with severe ulceration of the intestinal wall. These fungi are of particular importance when animals are being treated for long periods with antibiotics which may destroy the normal protective bacteria in the gut leaving the way open for the fungi to become established.

Diagnosis can be difficult and relies upon identifying the fungi in biopsy of the gut and lymph nodes. The condition can be easily mistaken for cancer by signs and appearance.

Treatment is also very difficult and requires both surgical removal of the effected gut and prolonged antifungal drugs such as Ketoconazole or Amphotericin B