What are Acute and Chronic Aspergillosis?

Usually a disease of the respiratory system, Aspergillosis is caused by the fungus Aspergillus, impacting chickens and turkeys, and less often, ducklings, pigeons, canaries, geese and other birds (both wild and those kept as pets). While the disease may be endemic on farms, in wild birds it often impacts an individual bird. Most often the birds that develop this disease are between the ages of 7 and 40 days.

Aspergillosis is a disease of the respiratory system caused by the fungus Aspergillus that impacts chickens and turkeys, as well as other birds less frequently.

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Symptoms of Acute and Chronic Aspergillosis in Birds

Aspergillosis may be acute or chronic. Those birds with the acute form of the disease may display the following symptoms:

  • Having a very difficult time breathing
  • Decrease in or loss of appetite
  • Drinking and urinating more often
  • Mucous membranes and/or skin turning bluish in color
  • Sudden death

Birds with the chronic form of aspergillosis, which is more common, may not show symptoms until the disease has progressed to the point where it cannot be cured. In the chronic form, respiratory symptoms are often the first to be seen. This will include trouble breathing, breathing quickly or struggling to exercise. When the voice box is affected, you may notice a change in the bird’s voice, an unwillingness to talk or a clicking. Other symptoms will depend on which organs are involved. Should there be central nervous system involvement, the bird may experience:

  • Tremors
  • Uneven gait
  • Seizures
  • Paralysis

Nonspecific symptoms may include:

  • Lack of appetite leading to weight loss
  • Wasting of muscles
  • Gout
  • Diarrhea or abnormal feces
  • Urinating excessively
  • Appearing lethargic
  • Appearing depressed

Types 

In the acute form of the disease the fungus will typically impact the trachea, voice box and air sacs. In some cases, there is lung involvement. The condition is usually diagnosed by an examination after the bird has died.

In the chronic form, which is more common, the condition is more deadly. The primary place of infection is the respiratory system and white nodules will show up and will wear away the tissue, with large amounts of spores entering the bloodstream. These spores make their way through the bird’s body and infect multiple organs, to include the brain, liver, kidneys, muscle, gastrointestinal tract,  and eyes. The spores can also impact fresh or incubating eggs and will cause death in the embryos.

Causes of Acute and Chronic Aspergillosis in Birds

Aspergillosis is a respiratory disease that is caused by the Aspergillus, which is a fungus that is found in most places in the environment. The most common species of the fungus that causes disease is A. fumigatus; A. flavus and A. niger as well as other species can cause issues. Aspergillus will grow more easily in places that are warm and moist. When spores of the fungus become airborne, particularly in places with poor ventilation and sanitation and/or that are dusty and confined, there will be a greater chance that spores will be breathed in.

Infection can occur when chicks are hatching should they inhale a large number of the spores in hatching machines or from litter that is contaminated. Birds that are older will usually be infected by inhaling dust from litter, feed or range areas that are contaminated with the spores. 

Typically, inhaling the fungus does not lead to disease, though if the bird lacks a healthy immune system, illness can occur. Certain factors predispose birds to developing the disease, which include:

  • Other illness
  • Stress
  • Poor nutrition
  • Residing in unsanitary conditions
  • Poor husbandry
  • Injury to their respiratory system
  • Use of certain medications (for example antibiotics and corticosteroids).

In pet birds, the disease is more common in parrots and mynahs than other birds.

Diagnosis of Acute and Chronic Aspergillosis in Birds

It can be challenging to diagnose aspergillosis as the symptoms will be similar to those of other illnesses, particularly those experiencing the chronic form of the condition. Your veterinarian will ask you for information regarding the symptoms you have noticed, when they were first noticed and what changes you have witnessed. You will also be asked for information about diet and husbandry of the bird. Tests may include x-rays, a complete blood count and a chemistry panel, and endoscopy may be used to look at lesions on the voice box and/or trachea.

Samples may be taken for a culture or microscopic exam. PCR testing may also be conducted to determine if Aspergillus is present. While a blood test panel may point toward aspergillosis, in some cases is will return a false positive or a false negative, meaning that the tests must be considered in conjunction with other findings. Should a bird be infected with the acute form of the disease, the diagnosis is usually made during an exam after its death.

Treatment of Acute and Chronic Aspergillosis in Birds

In regards to treatment, antifungal drugs may be administered to your bird (itraconazole and amphotericin B). These can be given by mouth, topically, through injection, or nebulizing and will depend upon the particular drug. The medication will need to be given for a period weeks to months and in some cases more than one antifungal drug will be used. 

In addition to medication, supportive care may be helpful to include oxygen, heat, feeding by a tube, and providing treatment for any underlying conditions. Surgery may be recommended to remove any lesions. During treatment, prognosis is guarded.

Recovery of Acute and Chronic Aspergillosis in Birds

Good husbandry and diet are imperative to keep there from being aspergillosis outbreaks. Birds should be kept in an environment that is well-ventilated with clean food and water dishes. The bottom of your bird’s cage should be cleaned often and your bird should be removed from the cage while his environment and other items are thoroughly cleaned (at least monthly). Alleviating stress in your bird’s life is also important in helping him avoid developing disease.