| | | | | Owners & Enthusiasts | | | | | | ASPERGILLOSIS SINUSITIS | | | | | By Fern Van Sant, DVM
For the Birds
Aspergillus sp. is a ubiquitous soil saprophyte that is the causative agent of a number of disease syndromes in avian medicine. It is regarded as an opportunistic pathogen and disease caused by this organism usually implies some degree of immune system compromise.
In pet birds there are numerous conditions of conventional management that predispose pet birds to aspergillosis. Environmental and nutritional status can play a significant role in this disease process. An understanding of the underlying processes involved is imperative in successfully treating this disease.
Many of the commonly accepted practices of companion bird management contribute to the frequency of this disease. Many of our companion birds are maintained or diets composed largely or entirely of seed. This ration is lacking in many vital nutrients, most notably vitamin A and minerals.
Unfortunately, a lack of vitamin A leads to changes in the squamous epithelium lining respiratory passages. These predictable changes in cellular structure translate into decreased function.
The normal clearing and local immune functions that protect against respiratory disease are depressed or lacking.
This commonly puts the bird at risk for significant disease. Aspergillus sp. is one of a host of potential pathogens that can cause disease in these situations.
The use of bedding on the cage floor is often adopted for esthetic reasons but can be poorly maintained and often moist due to water spillage and droppings. The most common bedding available is ground corncob. Aspergillus grows readily in this litter, and the litter itself is often seeded with aspergillus spores.
Poor ventilation and dusty environments can contribute to this process by contributing to conditions of airway inflammation. Other respiratory irritants such as second hand cigarette smoke, smoke from fireplaces or wood stoves, or aerosolized chemicals can contribute.
Aspergillosis occurs in two principal forms, acute and chronic. The acute form usually results in the formation of milliary granulomas from inhalation of an overwhelming number of spores.
Acute aspergillosis is usually fatal. The chronic form usually occurs when a bird is unable to eliminate or contain even a small number of aspergillus spores. The prognosis in this case usually depends on the site of the primary infection and the immune status of the host. Unfortunately the primary lesion is often in an airway and usually in a site with minimal blood supply. Aspergillus granulomas are often seen in the trachea at the chorina.
It is speculated that the frequency of lesions at this site in due to airflow patterns. This same explanation can account for air sac lesions.
Aspergillus sinusitis is not commonly reported. Most reported sinusitis cases are attributable to hypovitaminosis A or bacteria. The external site of these infections makes the process somewhat easier to manage and diagnose. The presence of an aspergillus granuloma in an accessible sinus can indicate a limited process or can be a sign of systemic disease.
Diagnosis of this disease is often challenging and patients often present in an advanced stage of a chronic process. Dyspnea, debilitation and emaciation are common presenting signs. Management history can be crucial to diagnosis. Stabilization of the patient is crucial with supportive care that will usually include oxygen, heat and fluids. Diagnosis can be obtained with radiographs, endoscopy, cytology and culture. High WBC counts and a low-grade anemia are expected in this disease. Titers for aspergillus antibodies can be run, but results can be inconclusive in psittacines.Many severely affected birds have no measurable antibodies. Treatment with antifungal agents should be started quickly and continued for months. Amphotericin B remains the initial treatment of choice followed by oral itraconazole and nebulization of an antifungal drug.
It is imperative that the predisposing factors of diet and management be identified and corrected if therapy is to be successful. Depletion of specific nutrients can result in whole body changes that are potentially reversible. Reversal of these processes will largely depend on the stage of debilitation of the patient.
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