Aspergillosis in birds: diagnosis and treatment

Aspergillosis is one of the most common and dangerous fungal infections in pet birds, caused by the mould Aspergillus fumigatus. It is particularly insidious because it develops slowly and shows few obvious symptoms until well advanced — earning it the nickname "the silent killer" in aviculture.

How birds get Aspergillosis

Aspergillus spores are everywhere in the environment — in dust, soil, hay, decaying plant material, and mouldy food. Most healthy birds with intact immune systems inhale spores regularly without getting ill. Disease develops when:
- The bird is immunocompromised (from another illness, nutritional deficiency, stress, or prolonged antibiotic use)
- The bird is exposed to an unusually high spore load (mouldy food, dusty hay, poor ventilation)
- Certain species are inherently more susceptible — African Greys, Amazon parrots, and goshawks are at particular risk

Forms of aspergillosis

- Acute (systemic): rapid onset, severe respiratory distress, septicaemia. Often rapidly fatal.
- Chronic (localised): more common in pet birds; granulomas (fungal nodules) form in the air sacs, lungs, trachea, or sinus. Progresses slowly over weeks to months.

Symptoms

- Breathing changes: tail bobbing (the tail moves with each breath), voice changes, open-mouth breathing in advanced cases
- Weight loss and muscle wasting
- Lethargy, decreased interest in food
- Nasal discharge or crusty nostrils
- Neurological signs if the infection spreads to the brain (rare)
- The bird may appear relatively normal until the disease is well established

Diagnosis

Diagnosing aspergillosis is genuinely challenging:
- Blood tests (haematology, plasma protein electrophoresis, Aspergillus serology) provide clues
- Radiographs may show air sac thickening or density changes
- Endoscopy of the air sacs under anaesthesia is the most definitive method — granulomas are directly visible
- PCR on respiratory samples

Treatment

Treatment is prolonged (months) and expensive:
- Voriconazole is currently the antifungal of choice for most pet birds
- Itraconazole is another option, particularly for less severe cases
- Nebulisation with antifungal drugs (amphotericin B or clotrimazole) delivers drug directly to the respiratory tract
- Surgical removal of accessible granulomas

Prognosis depends entirely on how early treatment begins. Early-stage disease in a well-supported bird has a reasonable prognosis; advanced disease is often fatal despite treatment.