They are often lethargic and easy to approach. Some infected birds may show no outward signs, but are carriers of the disease and can spread the infection to other birds. Occasionally, outbreaks of the disease cause significant mortality in certain species. Healthy birds normally resist the disease, but birds with depressed immune systems are especially vulnerable. External symptoms include difficulty in breathing, emaciation, and increased thirst.
Birds also can appear to have difficulty walking.
When their eyes are infected, there may be a white opacity in one or both eyes, accompanied by a discharge. Aspergillosis is a mold infection that is usually caused by Aspergillosus fumigatus , commonly found in decaying vegetable matter. A bird becomes infected by the ingestion or inhalation of mold spores from contaminated foods. The infection causes lesions in the lungs and air sacs and has been reported in many species of birds. Occasionally, outbreaks of the disease cause significant mortality in certain species.