Steven R. Brown1, DVM; Peter Noah2, BS
Discussing one's treatment of avian aspergillosis can be a very humbling exercise. Much of the scientific information available about this most common of the avian mycoses comes from the poultry industry. There-in lies some inherent problems when protocols for a short lived species are applied to raptors, caged pet birds or captive sea birds.
The ubiquitous organism Aspergillus fumigates is considered the most common etiologic species in avian aspergillosis. The most accepted theory suggests that birds become vulnerable to the disease when intrinsic or extrinsic factors create immunosuppression or when there is an overwhelming exposure to the fungal spores. Aspergillosis presents a very ominous threat to captive sea birds.
The Oregon Coast Aquarium has an exhibit collection of over one hundred birds including tufted puffins (Lunda cirrhata), pigeon guillemots (Cepphus columba), rhinoceros anklets (Cerorhinca monocerala), common murres (Uria aalga), and oyster catchers (Hamatopus bachmani). The majority of these birds were collected as chicks from the Alaskan coast. Several adult tufted puffins are on breeding loan from Sea World of Florida and Texas. All of the birds are maintained in a 7,000 sq. foot outdoor walk through aviary that recreates rocky cliffs and an earthen hillside. There are two pools holding 12,000 and 17,000 gallons of sea water to which the birds have free access.
To date we have diagnosed 26 cases of aspergillosis in our sea birds. Diagnosis has been based upon multiple parameters: post mortem exam, observation history and physical (lethargy, anorexia, weight loss, dyspnea, paralysis) hematology (leukocytosis), tracheal cytology/culture (very unreliable for us; many false negatives), ELISA antibody at Raptor Center university of Minnesota (unreliable for us; false negatives), radiography (granulomas, thickened air sacs, splenomegaly, hepatomegaly), and endoscopic evaluation. Our first cases in a population of less than one year of age predominately involved pigeon guillemots leading to 30% mortality of that species (no new cases in 2yrs). Our second highest incidence has been in tufted puffins with a mortality rate of 20% spanning three years and a variety of age groups. It is interesting to note that only one case of aspergillosis has been diagnosed in our population of twenty three rhino cerous anklets, and six black oyster catchers.
Our first attempts at treatment were rather "traditional" and far from satisfactory. Protocols included the following medications: fluconazole (l0mg/kg po bid l), flucytosine (125mg/kg po bid), amphote4ricin-B (1mg intratracheal qd), and ketoconazole (10mg/kg po bid). Fluid and nutritional support was minimal based upon the premise that extra handling was unduly stressful. With this approach our mortality rate was 100% with survival from detection to death ranging from 0 -30 days (mean 9 days).
In July of 1992, thanks to Sea World of California we were introduced to Itraconazole. This fungistatic agent has become the backbone of our aspergillosis treatment following much trial and error. Attempting to minimize the guess work and errors, mycolic identification and susceptibility testing was preformed from post mortem specimens. Aspergillus fumigates was confirmed demonstrating susceptibility to itraconazole and amphotericin-B at 0.lug/ml and 0.1\ug/ml respectively. Similarly, resistance was noted for fluconazole, and only moderate susceptibility to ketaconazole (MIC 1.6ug/ml) and fluorocytosine (MIC 6.25 ug/ml). Kidney and liver tissue concentrations were evaluated on a tufted puffin that had received itraconazole 30mg/kg po bid for 30 days and untreated bird tissues were used as a control. The laboratory reported a liver concentration of 0.61ug/ml, kidney concentration of <0.5 ug/ml and zero concentration respectively. Subsequently, sufficient air sac tissue was harvested from a tufted puffin that had received itraconazol (20mg/kg po bid) and enilconazole nebulization for tissue testing. Results indicated the air sac tissue concentration of itraconazole to be 8.3 ug/ml. (Testing for enilconazole is not currently available).
With this information in hand we were satisfied that itraconazole was an appropriate medication for our strain of Aspergillus, and that we were achieving more than adequate tissue concentrations to exceed the mean inhibitory concentration (MIC). Our patients' survival statistics had greatly improved, (40% survival rate, 1 to 619 + days, average 221 days). Liver and kidney histopathology from post mortem specimens found no evidence of drug toxicity. Frequent hematology and serum biochemical evaluation gave us further evidence to support the safety of itraconazole at 20mg/kg of body weight given orally twice daily. Even so, we were still losing some birds, especially tufted puffins, to aspergillosis.
Currently, birds identified with clinical aspergillosis receive itraconazole 20mg/kg po bid and amphotericin-B nebulized (amphotericin-B .2cc (5mg/ml), saline 2.0cc (0.9%)) three to five consecutive days (following pre nebulization with 0.5cc aminophylline (50mg/ml), 0.5cc saline (0.g%), 0.25cc acetylcysteine 20%, 0.lcc DMSO 90%) per ten day cycle. Six milliliters of enilconazole (l-50 dilution with saline) is nebulized with 0.lcc DMSO for 45 minutes on days alternate to amphotericin-B in severe cases. Under weight and anorectic birds are gavage fed twice daily. Isotonic fluid therapy is administered on an as needed basis. This regime has provided the most promising results to date.
There remains many unanswered questions:
1. if immunosuppression is a primary factor in these birds is it a deficient cellular or humoral response? or both?
2. if we attempt to stimulate the cellular immune response how do we measure the response in a clinical setting?
3. will "vaccination" prove to be beneficial?
4. will a vaccine" stimulate a cellular response as well as a humoral response?
5. are there other factors such as a predisposing virus that leads to immunosuppression and subsequent aspergillosis?
Aviary staff Oregon Coast Aquarium, Newport, OR, Veterinary Diagnostic Laboratory, Oregon State University, Corvallis, OR
1. Diflucan, Roerig Pharmaceutical, New York, NY
2. Ancobon, Roche Laboratories, Nutley, NJ
3. Fungizone, Pharma-tek Inc., Huntington, NY
4. Nizoral, Janssen Pharmaceutical Inc., Piscataway, NJ
5. Sporanox, Janssen Pharmacoutical, Titusville, NJ
6. Microbiology Reference Laboratory, Walker St., Cypress, CA
7. Fungus Testing Laboratory, University of Texas Health Sciences Center, San Antonio, Texas