Aspergillosis

Aspergillosis

Causative Agent

A disease of the respiratory tract, primarily of birds. It is caused by a fungus, Aspergillus, usually A. fumigatus.
Aspergillus fungi live on dead or decaying matter that are closely related to human activities such as decaying vegetation and feed grains.

Distribution

Geographic:

Seasonality:

Outbreaks of aspergillosis in waterfowl occur usually in the fall and early winter.
Individual cases of aspergillosis can occur throughout the year, particularly among birds undergoing stress such as malnutrition or suffering from another disease.

Click on a photo to enlarge.

Laboured breathing and gaping are often observed in birds suffering from aspergillosis.

Lung of bird with chronic aspergillosis showing "cheese-like" fungal plaques (at arrows).

Hosts, Transmission and Life Cycle

Hosts:

Aspergillosis is most often encountered in birds; rarely in mammals.
In young birds, particularly of northern waterfowl (eiders, mergansers), infection may spread (become generalized) and affect the brain.
All birds are susceptible to aspergillosis. It is most commonly observed in colonial waterbirds (gulls), waterfowl, ravens and crows (corvids), and captive birds of prey.

Transmission and Life Cycle:

Aspergillus spores are ubiquitous in the atmosphere and are continually inhaled by vertebrates.
Spores travel through the upper respiratory tract to the lungs where they may colonize and produce a fungal pneumonia. The lungs become obliterated with debris and fungal filaments.
Air sacs, parts of avian respiratory systems located primarily in the abdomen and long bones of wings, may also become infected. Dispersal of fungi to organs adjacent to air sacs may also occur.
Aspergillosis is not usually considered contagious.

Signs and Symptoms

Typically, birds infected with aspergillosis will be emaciated, exhibiting severe difficulty in breathing, appear “unthrifty” and weak, their wings may droop, and they may fail in attempts to escape if pursued.
Infection that has reached the brain can result in loss of muscular coordination and twisting of the head and neck so they are held in unnatural positions.
Variously sized lesions in the lungs and air sacs are often visible in chronic infections of aspergillosis, occurring as flattened, yellow plaques with a cheese-like appearance and consistency.
Similarly, large masses of fungal growth resembling bread mould may line air sacs.

Meat Edible?

Birds with aspergillosis should not be considered edible because they are often in poor body condition. While it is not possible for humans to contract aspergillosis from eating the meat of an infected bird, it is possible for humans to contract this disease from inhaling the spores that are present in the air sacs and lungs. Because of this, infected birds should be discarded and not consumed.

Human Health Concerns and Risk Reduction

Aspergillosis is considered a zoonotic disease. If resistance to infection is impaired, inhalation of Aspergillus fungi may lead to fungal pneumonia or a serious allergic reaction to the fungus.

Samples for Diagnosis

The whole carcass should be submitted for necropsy. The presence of fungal infection can be confirmed microscopically in the laboratory.

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