Diseases and conditions

Aspergillosis

Aspergillosis is the name given to the disease caused by infection by the Aspergillus genus.

Aspergillus is a fungus. The fungus spreads by creating threadlike structures, called hyphae. This allows it to expand over a large area. It multiplies by forming spores. Spores are microscopic reproductive units that are spread through the air.

 

Aspergillus fumigatus is the most common Aspergillus species to cause disease in birds. Aspergillus flavus and Aspergillus niger are also found, although less often.

It is a fungus that occurs naturally almost everywhere in the environment. Birds can be infected by breathing in the spores. Whether or not infection by the spores causes illness depends in large part on the physical condition of the bird. A healthy bird that is given quality feed with all the nutrients it needs, will usually be able to combat the inhaled spores and not become sick.

If infected by large amounts of spores, even a healthy bird can develop a disease.

Birds can also be more susceptible to an infection by Aspergillus after having been treated with antibiotics and medicines that weaken the immune system (corticosteroids).

 

If the Aspergillus cannot be cleared by the body's immune system, it will multiply and cause disease. The biggest problems are often seen in the respiratory system of birds.

 

Aspergillosis can either be acute or chronic in its nature. In its acute form, the fungal spores attack several parts at once and often cause a large infection throughout the entire body. Besides damaging the respiratory organs, it will also affect the liver and kidneys. The bird will become ill within a very short time, will refuse to eat and have difficulty breathing. They often drink much more than usual and the stool can have a green colouration. They can even die without showing any clear symptoms of illness.

 

The chronic form is more common. The fungi gradually grow from within one or more parts of the body (this usually starts in the respiratory system). They form lesions and granulomas (nodular masses) of fungal tissue.

The fungus can have an impact on several parts of the body. Fungal lesions may appear in the nose or at the back of the mouth, but can also often appear in the air sacs. They cover the air sac linings and can even block the connection to the lungs.

Spores that are formed spread slowly throughout the whole body. This can be an extremely insidious process. The birds don't become acutely ill, but have a weaker physical condition, are lethargic and sleep more. Shortness of breath is a common symptom, particularly after exertion.

If the fungus in the windpipe is close to the syrinx (birds' vocal organ), it can cause the voice to change.

Due to the nature of this disease, help is usually only sought once the fungus has spread to many parts of the body. This can make treatment of the disease very difficult. In its chronic form, sudden deterioration can sometimes occur. This could be the result of fungal granulomas eroding and blocking a section of the windpipe. This causes the bird to have severe breathing difficulties and should therefore be seen as an acute life-threatening situation.

 

Diagnosis

Aspergillosis can be diagnosed in several ways. One method is by collecting a swab culture from the nose, back of the mouth and upper part of the trachea. The collected material can then be examined under a microscope, showing the hyphae (fungal growth).

If the fungal infection is restricted to the air sacs, swabs taken from the upper airways will give a negative result. Diagnosis can be made by looking directly in the air sacs. This can be done with an endoscope, a small camera at the end of a very thin tube. The endoscopy will show the lesions and granulomas that cover the linings of the air sacs.

 

X-rays and blood tests can definitely help in diagnosing this disease, but don't always provide a clear picture.

 

Treatment

The fungus can be treated in a number of ways. Because of the extensive nature of the disease, one thing all treatments have in common is that they will take a long time.

In June 2014, a new anti-fungal medicine came on the market. This medicine is specifically developed for the treatment of birds. Extensive research was conducted on birds to be sure it is both safe and effective.

The medicine contains itraconazole, an agent that stops fungal growth and damages the outer layer of the fungus. The bird's own immune system can then take over and get rid of the remaining fungus. The medicine can be given orally, either directly in the beak or mixed with feed.

 

If large fungal granulomas are found in the windpipe, nose or air sacs, an attempt can be made to operatively remove them, even partially. This means the bird must be put under general anaesthesia.

 

 

Besides treating the fungus itself, it is also very important to establish any underlying causes. This often involves changing the diet of the bird. Other infections, such as viral or parasitical infections, can weaken the resistance, allowing the fungus infection to prosper.