Aspergillus grows readily in warm and moist environments. The microscopic spores of the fungus become airborne, and poor ventilation, poor sanitation, dusty conditions, and close confinement increase the chance the spores will be inhaled. Usually the fungus itself does not cause sickness, however, if the immune system is compromised through such things as poor nutrition, poor husbandry, poor sanitation, it can cause illness.
Aspergillosis can follow one of two courses, acute or chronic. Birds with acute aspergillosis have severe difficulty breathing, decreased or loss of appetite, frequent drinking and urination, cyanosis (a bluish coloration of mucous membranes and/or skin), and even sudden death.
The fungus generally affects the trachea, syrinx (voice box), and air sacs. The lungs may also be involved. Diagnosis is generally made through a post-mortem examination. Chronic aspergillosis is much more common, and unfortunately, much more deadly due to its insidious nature. The bird may not become symptomatic until the disease has progressed too far for a cure. The respiratory system is the primary location of infection. White nodules appear and ultimately erode through the tissue, and large numbers of spores enter the bloodstream. The spores then travel throughout the body, infecting multiple organs including kidneys, skin, muscle, gastrointestinal tract, liver, eyes, and brain. Spores can also penetrate fresh or incubating eggs and kill the embryo.
Diagnosis of avian Aspergillosis can be difficult, at best, other than by autopsy as in the chronic form it mimics other diseases. The veterinarian will need a detailed history of the course of the illness, and an accurate description of the diet and husbandry of the bird. Additionally, your avian veterinarian should take samples and attempt to culture the fungus in specially prepared culture media. Blood should also be submitted for serologic evaluation.
Antifungal drugs, such as itraconazole, ketoconazole, terbinafine, flucytosine, and amphotericin B, may be administered orally, topically, by injection, or nebulizing, depending upon the drug. In some situations, surgery may be necessary. Each treatment protocol has to be tailored to the individual bird. Therapy may continue for weeks or months depending on situation of underlying conditions.