ASK THE VET (ASPERGILLOSIS - PART II Diagnosis of Aspergillosis)

Aspergillosis is the most frequently occurring fungal infection in birds. All species are susceptible. It may be contracted as the result of inhalation of fungal spores or oral ingestion, especially if birds are fed moldy food or housed on contaminated bedding.Immunocompromised and malnourished birds are most susceptible to the disease.

Diagnosis of aspergillosis can be difficult. A tentative diagnosis may be made of the basis of physical findings, a history of environmental conditions suitable for fungal growth, and recent stress. A hemogram may show a significant leukocytosis (elevated white blood cell count) with a heterophilia early in the disease. As the disease becomes more chronic, a monocytosis, lymphopenia, and non-regenerative anemia develop. An increase in total blood protein with a hyperglobulinemia may develop. Deep tracheal cytology and culture may be performed under anesthesia. A positive culture will usually be present in 18 hours. A single colony growth is considered significant.

Endoscopic examination of the respiratory tract and abdominal cavity will allow cultures to be taken and granulomas (large walled-off areas) visualized.

An indirect ELISA blood test will permit the detection of antibodies, which will be present within a week of exposure to a large number of spores. This test permits detection of a patient early in the course of the disease, before clinical signs become apparent. Antibody titers decline during remission, and thus this test is useful in monitoring a patient's response to treatment. Unfortunately, an infected bird may fail to show a positive titer due to a poor immune state.

Radiographs may be helpful in supporting a diagnosis of aspergillosis. Hyperinflation of air sacs in the lateral and ventraldorsal views is the classic presentation. This occurs as a result of stenosis near the syrinx or mainstem bronchi which results in the trapping of air in the caudal air sacs. Nodular densities may be present in the air sacs and lungs. Loss of definition of air sac lining may occur early in the disease. Asymmetry of the air sacs as a result of air sac collapse, hyperinflation, or filling with necrotic material may be present.

Treatment of aspergillosis involves several objectives:

2. killing and eliminating fungal organisms, and

3. supportive care