THE DISEASE OF THE MONTH
"ASPERGILLOSIS"
by Diane Wanamaker, Certified Avian Specialist
Real Macaw Parrot Club Member
The disease Aspergillosis (as'per ji lo' sis) is caused by fungal spores that are found everywhere in the environment. The Kingdom Fungi includes molds, mushrooms and yeast. Fungus lack chlorophyll and digest food externally, absorbing the small nutrient molecules that result. They have body structures and methods of reproduction unlike any other organism. A typical fungus consists of a net-like mass of filaments called hyphae. Fungus reproduce by producing spores that contain half the number of chromosomes found in the mature fungus. Fungi flourish in damp, dark places where organic material is available for them to feed on.
Aspergillosis can not be spread from bird to bird. Most companion birds are highly resistant to this fungus. A bird can only be infected when exposed to a huge number of spores or when their immune system is weakened. Chronic disease condition, poor diet, poor ventilation, lack of sunlight, overcrowding, antibiotic therapy, corticosteroid treatments, respiratory irritants and stress are some conditions that could weaken the immune system. Birds should not be exposed to damp nesting material, plant potting soil, peat moss, wet shavings or other litter, and contaminated corn and peanuts.
According to Louise Bauck, DVM in Avian Medicine: Principles and Treatment, the birds that are believed to be especially susceptible are Penguins, Birds of Paradise, waterfowl (especially diving birds and shore birds), Goshawks arid Gyrfalcons. Aspergillosis is commonly seen in African Greys and Amazon parrots.
Since Aspergillus (the fungus that causes this disease) most commonly causes respiratory problems, I will describe the different parts of this system. In the August edition of Bird Talk Magazine, Margaret Wissman, DVM presents an excellent article explaining the where, what and why of avian respiratory systems. The diagram used is taken from Avian Medicine: Principles and Treatment. I suggest you read this article to help you better understand this system and its diseases. The trachea (the wind pipe) begins at the back of the bird's mouth and ends in the lungs. At the far end of the trachea is the syrinx (sir'inks) which parrots use to make sounds. Parrots have paired lungs, just like humans, that are located near their back. Avian (birds) lungs are expandable to a certain point, but are unlike human lungs which can greatly expand to fill with air. The avian lungs are connected to the syrinx by the primary bronchi. We flavor alveoli, where oxygen exchange takes place. Birds have air capillaries that perform this function. Most birds have four paired air sacs and one single air sac that connect to the lung and help create a large respiratory capacity.
Kevin Flammer, DVM reports that acute (sudden and severe) infections occur when the fungus affects the syrinx and essentially blocks the trachea. Birds affected this way might have a voice change followed by severely labored breathing. Affected birds will often breathe through their mouth and stretch out their necks in an attempt to breathe. Death may occur in a matter of days. More commonly, Aspergillus causes a more chronic (long term) infection. Louise Bauck, DVM writes, "The first signs are subtle and are often missed. As the fungus spreads through the lungs and air sacs, it forms large masses. Affected birds show severe weight loss, depression and intolerance to exercise. Labored breathing may or may not occur. Signs of labored breathing are open mouth breathing, tail "bobs" (the tail moves forward with each inspiration)." When observing a loud parrot (like my Amazon), you can see normal tail bobs when they scream. Tail bobbing (or pumping) associated with breathing in a resting bird is never normal. Louise Bauck also states that, "Wheezing, squeaking or loud raspy breathing are also indications of respiratory distress. Aspergillosis may be associated with ascities (fluid in the body cavity) caused by peritonitis (inflammation of the membrane that lines the abdominal cavity) or cardiopulmonary impairment (heart and lung problems)." These symptoms are usually the result of fibrous clots caused by the fungus in the blood supply to and from the lungs.
Aspergillosis causes the destruction of nearby affected tissue that could include bone or beak. Aspergillosis that infects the nasal cavity typically involves dry lesions and destructive swelling in one nostril. Tracheal or syringeal lesions usually occur as plugs of creamy white necrotic debris (dead tissue) at or near where the trachea and the primary bronchi meet.
Dr. Louise Bauck reports diagnosis of this disease could include; history, physical findings and blood counts (high white blood cell count and anemia). Fungal culture, blood studies, cytology (examining cells under the microscope), radiology (x-ray) and endoscopy (internal observation via a small diameter telescope) or exploratory surgery are among the methods used to diagnosis infections. If Aspergillus is found without other related symptoms it may not be an indication of this condition, because these spores are found normally in the environment. Aspergillus can occasionally be found in a culture from the cloaca (vent) or feces (poop). This fungus rarely affects the digestive tract, but this could be an indication that the bird is exposed to a large number of spores. Radiographic (x-rays) findings could be negative or show enlargement of the abdominal air sacs, dense spots in lungs or air sacs, loss of definition in the body cavity, air sac walls and opaque areas (white areas) of abdominal air sacs. A tracheal wash (saline is put down the trachea and then recovered) can be examined for the presence of fungal hyphae and cultured. An ELISA test (Enzyme-linked immunosorbent assay) which is a diagnostic test that can be used to detect the presence of anti-Aspergillus antibodies.
Dr. Louise Bauck writes, "Treatment of Aspergillosis is difficult, expensive and has a poor success rate in chronic infections. Surgical removal of infected areas should be employed if possible. Flushing areas with antifungal drugs may be helpful, but should be exercised with caution." The drugs used to treat this disease should only be used with veterinary supervision. The course of medication could last for months. Employing good hygiene and reducing exposure to sources of infection are the keys to preventing this disease. Kevin Flammer, DVM recommends providing a good diet and avoid feeding dried corn and damaged peanuts (buy human grade produce from health stores). Reducing exposure to damp bedding and nesting materials will help control this disease. He also advises not to let your birds play in potted plants. Now that we know the fungus can be among us, we can take safe guards to protect our birds' health.
Bauck, Louise, DVM. Avian Medicine: Principles and Application. Branson Ritchie, DVM, PhD. Greg Harrison, DVM. Linda Harrison, BS. Lake Worth, Florida, Wingers Publishing, Inc. 1994. 1000-1004.
Flammer, Kevin, DVM. "Aspergillosis". Proceedings of International Aviculturists Society. January 10-14, 1996.
Harrison, Greg. J., DVM. Tully, Thomas Jr., DVM. "Pneumonology, The Respiratory System". Avian Medicine: Principles and Application. Branson Ritchie, DVM, PhD. Greg Harrison, DVM Linda Harrison, BS. Lake Worth, Florida. Wingers Publishing, Inc. 1994. 560-567.
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