Aspergillosis in Chickens and Birds: Signs, Diagnosis and Prevention
Aspergillosis is a fungal disease that can affect poultry as well as parrots, pigeons, waterfowl, wild birds and many other avian species.
It is caused by fungi from the Aspergillus genus, most commonly Aspergillus fumigatus. These fungi are widespread in the environment and produce microscopic spores that birds can inhale.
Disease tends to occur when birds are exposed to very high numbers of fungal spores or when their normal defences are compromised.
Where Does Aspergillosis Come From?
Aspergillus thrives in warm, damp environments, particularly where organic material is present.
Potential sources include:
- Mouldy bedding or litter
- Damp feed
- Mouldy hay, straw or mulch
- Poorly cleaned incubators and hatchers
- Contaminated ventilation systems
- Damp housing
- Decaying vegetation and organic material
Young chicks can be particularly vulnerable when incubators, hatchers or brooding environments are contaminated with fungal spores.
In adult birds, disease is more likely following heavy environmental exposure or when birds are stressed, immunocompromised or suffering from another illness.
Signs of Aspergillosis
Because birds have a complex respiratory system involving both lungs and air sacs, respiratory fungal infections can become extensive.
Signs may include:
- Gasping or difficulty breathing
- Increased respiratory effort
- Changes to the voice or crow
- Reduced activity
- Poor appetite
- Weight loss
- Weakness
- Reduced egg production
- Eye or sinus swelling
- Nasal or ocular discharge
Neurological signs such as poor coordination, abnormal gait or head position can occasionally occur if infection becomes disseminated.
In severe flock outbreaks, birds may become sick and die relatively quickly.
What Does Aspergillosis Look Like at Post-Mortem?
One of the classic findings is the presence of white, cream or yellow fungal plaques or nodules within the respiratory system.
These may be found in the:
- Air sacs
- Lungs
- Trachea
- Sinuses
In disseminated disease, fungal lesions may also occur in other organs.
The appearance can be striking, but lesions alone don't necessarily identify the exact fungal species involved.
How Is Aspergillosis Diagnosed?
Diagnosis can be challenging because many of the clinical signs are nonspecific.
Depending on the bird and presentation, investigation may involve:
- Clinical examination
- Endoscopy
- Imaging
- Cytology
- Fungal culture
- Histopathology
- Molecular testing
- Post-mortem examination
Fungal culture can be useful, but because Aspergillus is common in the environment, results need to be interpreted alongside the clinical picture and other diagnostic findings.
Can Aspergillosis Be Treated?
Yes, but treatment can be difficult, particularly once disease is advanced.
Individual birds may require prolonged antifungal treatment, sometimes combined with nebulisation, supportive care or treatment directed at fungal plaques.
Treatment depends on the species of bird, severity and location of infection, so antifungal medications should ideally be selected and dosed under veterinary supervision.
Unlike bacterial infections, antibiotics do not treat Aspergillus.
Managing a Flock Outbreak
When multiple birds are affected, one of the most important questions is:
Where are the fungal spores coming from?
Treating individual birds without correcting the environmental source may simply result in continued exposure.
Investigating a flock outbreak should include checking:
- Feed storage
- Bedding and litter
- Ventilation
- Water systems
- Incubators and hatchers
- Brooding areas
- Damp areas
- Recently introduced organic material
- Compost, mulch, hay or decaying vegetation
Removing contaminated material and correcting moisture, ventilation and hygiene problems can be just as important as treating affected birds.
A Case From the Field
One free-range poultry flock we investigated experienced a sudden increase in illness and mortality.
Affected birds showed respiratory distress, neurological signs, eye swelling and reduced egg production. Post-mortem examinations revealed characteristic fungal lesions affecting multiple tissues.
One particularly important environmental finding was the recent addition of a large quantity of mulch to the ranging area.
Decaying organic material can provide excellent conditions for fungal growth. In this case, the timing and environmental findings made the mulch a suspected contributor to the high fungal exposure.
Cases like this demonstrate why flock disease investigation shouldn't stop at the individual bird.
Sometimes the most important diagnostic clue is sitting in the environment.
Prevention Is Key
Aspergillosis is much easier to prevent than to treat.
Good prevention includes:
- Keeping feed and bedding dry
- Discarding mouldy feed or litter
- Maintaining good ventilation
- Thoroughly cleaning incubators and hatchers
- Keeping feeders and drinkers clean
- Preventing moisture accumulation
- Monitoring organic material such as mulch, hay and compost
- Reducing unnecessary environmental stress
- Investigating unusual mortality early
For hatcheries and brooding facilities in particular, good hygiene and moisture control are extremely important.
The Takeaway
Aspergillus spores are everywhere. The presence of the fungus in the environment isn't unusual.
Problems arise when birds inhale large numbers of spores or their natural defences are compromised.
If multiple birds suddenly develop respiratory disease, particularly following changes to bedding, feed, housing or organic material in their environment, don't just look at the birds.
Look at the environment too.
Written by Dr Sam Hurley, BSc, BVSc, MAH
