|by Dr. David Phalen
A few brief comments on aspergillus. This is a disease that is most likely to occur in birds that are from environments where aspergillosis does not grow well (cool and dry or hot and dry environments). For some reason these birds have a poor ability to fight off this organism. Examples of these birds include sea ducks, ostriches, and penguins. The other predisposing factor is the density of spores. In buildings that are poorly ventillated spore density will increase. Less commonly we see individual animals come down with asper, even though they would not be considered at risk birds.
Successful treatment for asper depends on many factors. The location of the infection (nasal passages, trachea, airsacs, lungs), the extent of the disease by the time that it is recognized, and the immune status of the bird that has the infection all are critical factors. Asper grows like mold on bread inside the bird forming colonies on the respiratory surfaces. This elicits a response from the host that causes purulent material to build up around the colonies. The fungus is invasive and in advanced infections will invade into tissues and eventually into a blood vessel. Once a blood vessel is invaded the organism will spread to other organs and block blood vessels. The tissues whose vessels are blocked die. At this point treatment is not likely to be successful.
Treatment is also complicated by the fact that asper grows on the surface of airsacs where the blood supply is poor and lots of caseous material builds up in these areas. Therefore, it is difficult to get drugs directly to these locations.
Traditional treatment has been with itraconazole given orally. Usually this only has to be given once a day, but we treat until 1 month after the white blood cell count returns to normal, generally about 3 months. In my experience this drug has been very effective.
When the organism is in the trachea of the nasal passages, direct application of an antifungal to the lesion has been used in conjunction with systemic treatment. Amphotericin B has been applied directly into the trachea. This drug is caustic and complications from this therapy may occur. Nebulization with clotrimazole has been used in gyrfalcons with asper of the airsacs. I have used clotrimazole as an infusion for a bird with refractory nasal asper. This bird was also on intraconazole. Lamisil is an new drug that Dr. Bob Dahlhausen and others are using. There will be a paper presented at the AAV this year on this product. It may be better or as good as itraconazole. We will have to see.
If you wish to donate to avian research by Dr. Phalen, please send tax-deductible donations to:
David N. Phalen DVM, PhD
Department of Large Animal Medicine and Surgery
College of Veterinary Medicine
Texas A&M University
College Station, Texas 77843