Aspergillosis in Birds
Aspergillosis is a fungal infection that commonly causes respiratory disease in pet birds. It can cause both upper (nose, sinuses, eye, and trachea) and lower (lungs and air sacs – a specialized part of the respiratory tract that birds have) respiratory problems or more broadly distributed systemic infections.
What is aspergillosis?
Aspergillus is the fungus that causes an infection called aspergillosis. This slow growing fungal infection gradually damages tissues in the body over a period of weeks to months, often with little obvious evidence of illness until an organ or system is severely compromised. Aspergillus fungus exists in the environment as microscopic spores that are found everywhere, particularly in soil, moist nesting material, and moldy foods. The spores persist in the environment and are very resistant to disinfection.
"Birds on an all-seed diet may be more prone to this disease."
Aspergillus is normally an environmental contaminant and is not contagious from bird to bird. It more commonly affects birds whose immune systems have been compromised by other diseases or by malnutrition. Birds with healthy immune systems may be exposed to Aspergillus spores and not develop infection. However, even healthy birds exposed to large numbers of these spores (in dust, mold, soil, etc.) may be infected. Steroid use, long term antibiotic use, excessive stress, poor husbandry or hygiene, respiratory irritants (such as cigarette smoke), viral infections and other chronic infections can all cause immune suppression and lead to secondary infection with Aspergillus. Birds on all-seed diets may be more prone to this disease because seeds lack vitamin A, a nutrient essential to keeping both birds’ respiratory tracts and immune systems healthy.
How do I know if my bird has aspergillosis?
Birds with aspergillosis may show very non-specific signs, and infection may not be obvious early in the disease. Ultimately, infected birds may show signs of respiratory difficulty, including tail bobbing, or weight loss. The bird may be lethargic, fluffed, and listless. A veterinarian familiar with birds should start by collecting a complete history, measuring the bird’s weight, and performing a thorough physical examination. Since many of the clinical signs of aspergillosis are non-specific and common to several different diseases, a veterinarian will likely want to perform several diagnostic tests.
What tests can be done?
Many different tests may be employed if aspergillosis is suspected. Each test provides another piece of the puzzle, and often multiple tests are needed to give more clarity.
A complete blood count (CBC) with a dramatic elevation in the white blood cells may initially raise suspicion of an Aspergillus infection. X-rays may only show subtle lesions in early stages of disease. Later in the illness, changes potentially visible on X-rays include pneumonia, thickening of air sacs, and breakdown of bone. Serology (antibody) tests are available but can have false negative results because a healthy immune system is needed to mount antibody response, and many birds with aspergillosis have poorly functioning immune systems. Likewise, as Aspergillus spores are common in the environment, many healthy birds can have antibodies to this fungus, so false positive serology tests occur as well. DNA tests will detect the presence of Aspergillus DNA in blood or other tissues. A tracheal wash may document the presence of the Aspergillus organism in the trachea or respiratory tract; however, spores may be present in small numbers even in healthy birds. The most accurate diagnostic technique is surgical laparoscopy in which a fiber-optic endoscope is passed surgically into the bird’s airways to view the trachea, air sacs, lungs, and sinuses. Samples of lesions are collected for microscopic analysis and culture.
Can my bird be treated?
Aspergillosis is a very challenging disease to cure. The location of the infections and the way the body attempts to wall off the fungus both restrict the ability of drugs to get to the fungus. Treatment takes a long time. The bird must have a strong immune system in order to completely eliminate the organism. Treatments may include oral, intravenous, topical, and aerosolized antifungal medications and/or surgical removal of fungal plaques (concentrated areas of fungal growth). Supportive care includes hospitalization, oxygen therapy, providing warmth, force feeding, administration of anti-inflammatory medications, and treatment of other underlying or concurrent diseases.
"Aspergillosis is a very challenging disease to cure."
Good hygiene (to minimize dust and moisture build-up), frequent cage cleaning, fresh nutritious food, and good ventilation are all important in both treating and preventing outbreaks of aspergillosis in birds.
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