The disease, aspergillosis, is caused by a fungus belonging to the genus Aspergillus.  The species most frequently involved is Aspergillus fumigatus.  This organism is widely distributed throughout the world, commonly existing in soil or mouldy grain.

Aspergillosis occurs most frequently in birds but is occasionally reported from mammals.  Aspergillosis in birds is usually reported from waterfowl, game birds and species held in captivity.  Species of these groups of birds are examined frequently by man.  In Ontario the disease has been recorded as a mortality factor in a variety of birds including loons, gulls, pheasants and mallard, scaup and black ducks.

Lungs and air sacs are the primary sites of infection.  Yellowish-white caseated nodules varying in size up to that of a pinhead occur in lung tissue.  The walls of the air sacs may be thickened and in some cases covered with a growth of greenish mould.  Plaques or concentrically-layered concave discs may be observed on membranes of the body cavities.  Evidence suggests that birds are most susceptible to aspergillosis during periods of physiological stress.  Aspergillosis is usually, but not always, fatal.

Selected Reference:

Chute, H.L. 1965.  Diseases caused by fungi, pp. 494-511.  In: Biester, H.E. and L.H. Schwarte (eds.), Diseases of poultry, 5th ed.  The Iowa State University Press, Ames.