What Is Your Diagnosis?

Esther H. Greenbarg Department of Veterinary Biosciences and Diagnostic Imaging, College of Veterinary Medicine, University of Georgia, Athens, GA 30602.

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Scott A. Secrest Department of Veterinary Biosciences and Diagnostic Imaging, College of Veterinary Medicine, University of Georgia, Athens, GA 30602.

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History

A wild young adult bald eagle (Haliaeetus leucocephalus) was admitted to the University of Georgia Veterinary Teaching Hospital's Emergency Service after being found lying down by a good Samaritan. On physical examination, the bald eagle was responsive but dull and lethargic with drooping wings. It was estimated to be 10% dehydrated on the basis of a slow basilic vein refill time. The bird had a prominent keel and poor pectoral musculature, with a body condition score of 1 of 5 and body weight of 2.42 kg (5.32 lb). Hematologic evaluation revealed moderate anemia (PCV, 25%; reference range, 40% to 48%), heterophilia and monocytosis (estimated), a moderately high creatine kinase activity (1,066 U/L; reference range, 69 to 524 U/L), and mild to moderate hypoglycemia (157 mg/dL; reference range, 223 to 390 mg/dL). Assay results for serum antibodies against West Nile virus were considered positive, with a serum antibody titer of > 1:10. Orthogonal radiographs of the coelom were obtained (Figure 1).

Figure 1—
Figure 1—

Right lateral (A) and ventrodorsal (B) radiographic views of the coelom of a young adult female bald eagle (Haliaeetus leucocephalus) evaluated because of lethargy and drooping wings. R = Right.

Citation: Journal of the American Veterinary Medical Association 248, 9; 10.2460/javma.248.9.999

Determine whether additional imaging studies are required, or make your diagnosis from Figure 1—then turn the page →

Radiographic Findings and Interpretation

An increase in soft tissue opacity is evident in the mid ventral aspect of the coelom, which obscures the margins of the cardiohepatic silhouette. Throughout the lungs, numerous well-defined and ill-defined irregular soft tissue opacity nodules are seen, which are best identified on the ventrodorsal view (Figure 2). Additional ill-defined linear and nodular soft tissue opacities are visible in the area of the thoracic air sacs, caudal to the syrinx and dorsal to the heart. At the level of the fifth intercostal space, a thick, curvilinear soft tissue opacity is observed. Within the area of the proventriculus and ventriculus, gas and a minimal amount of mineralized ingesta are noted. The small intestine contains gas. No osseous abnormalities are identified, including on evaluation of radiographs of the extremities (not shown).

Figure 2—
Figure 2—

Same radiographic images as in Figure 1. Multiple pulmonary soft tissue nodules are seen within the lungs (arrows) and air sacs (black arrowhead). Thickening of the caudal thoracic air sac is evident as a conspicuous, curvilinear soft tissue opacity (asterisk). Gas is present within the area of the proventriculus and ventriculus (white arrowhead). See Figure 1 for remainder of key.

Citation: Journal of the American Veterinary Medical Association 248, 9; 10.2460/javma.248.9.999

Differential diagnoses for the soft tissue opacity nodules in the lungs and air sacs included fungal pneumonia and, less likely, neoplasia or bacterial abscesses. The curvilinear soft tissue opacities were consistent with thickening of the caudal thoracic air sac (airsacculitis) and concurrent coelomitis or neoplastic effusion.

Treatment and Outcome

The patient was initially treated with fluid therapy (200 mL/kg [91 mL/lb], SC, q 24 h), enrofloxacin (20 mg/kg [9.1 mg/lb], IV, once), orbifloxacin (20 mg/kg, PO, q 24 h), iron dextran (10 mg/kg [4.5 mg/lb], IM, q 7 d), vitamin B complex (3 mg/kg [1.4 mg/lb], IM, q 7 d), assisted feedings, and body temperature support. Although further diagnostic tests were considered (ie, respiratory endoscopy and sample collection), they were not performed because the bird began to show further signs of stress and an increase in lethargy. Treatment frequencies were reduced as a means to reduce patient stress. Two days after hospital admission, the patient was found dead in its cage.

Gross and histologic findings on necropsy indicated severe fungal pneumonia, airsacculitis, and coelomitis with effusion due to an Aspergillus infection. Fibrinous adhesions and Aspergillus colonies throughout the coelom suggested chronicity of infection. The mineralized ingesta were confirmed to be within the ventriculus.

Comments

Lethargy and drooping wings in birds can be due to a variety of disease processes with differential diagnoses including trauma, heavy metal toxicosis (particularly lead, although serum lead concentration was within reference limits in the patient of this report), fungal (aspergillosis) or bacterial (mycobacteriosis or chlamydiosis) pneumonia, and dystocia.1 Radiology was helpful in the case described in the present report to greatly refine the differential diagnoses for the patient's nonspecific clinical signs. Regardless of the species, fungal pneumonia and metastatic neoplasia are the most common differential diagnoses for multiple pulmonary soft tissue opacity nodules. However, given the frequency of fungal infections and the age of the patient, metastatic neoplasia was considered less likely than fungal pneumonia.2 Bacterial pneumonia was also considered less likely because it typically results in an interstitial to alveolar pattern in most species, with abscess formation less common.3 Dystocia and trauma were ruled out as a cause of the patient's clinical signs given the absence of radiographic changes consistent with these conditions. Therefore, the presence of multifocal pulmonary and air sac soft tissue opacity nodules on radiographs made fungal pneumonia the primary differential diagnosis, which was confirmed at necropsy. Airsacculitis is a nonspecific term for inflammation or infection of the air sacs that, when severe enough, can be identified radiographically as linear or curvilinear soft tissue opacities. In the bird of the present report, airsacculitis was due to a mixture of edema, inflammatory infiltrates, and the presence of a large number of fungal hyphae.

Aspergillosis occurs as a result of an overload of inhaled infective spores, usually in an immunocompromised animal. In the bird of the present report, assay results for serum antibodies against West Nile virus were positive, suggesting that this patient was immunocompromised as a result of a primary viral infection; however, it is also possible that the positive antibody assay results may have been an incidental finding reflective of exposure to rather than infection with West Nile virus. Aspergillus infection is common in both pet and wild birds and predominantly affects the respiratory tract, but can spread hematogenously to other organ systems.4 It occurs in acute and chronic forms in birds, both of which carry a poor prognosis. Clinical signs depend on organ system involvement and are often nonspecific, as was true for the bird of the present report. Respiratory signs such as tail-bobbing and open-mouth breathing are often not observed until end-stage disease.4 Antemortem diagnosis is often difficult, as is treatment. Prolonged systemic antifungal drugs such as amphotericin B or itraconazole are recommended, in addition to intensive supportive care and antimicrobials for secondary bacterial infections.

Because of the often nonspecific clinical signs of birds infected with Aspergillus spp and the common respiratory tract involvement in apparently eupneic birds, findings on radiography could raise suspicion for fungal infection in birds with otherwise vague clinical signs. Aspergillosis should be considered as a differential diagnosis for similarly affected avian patients with radiographic pulmonary and air sac soft tissue opacity nodules.

References

  • 1. Mayer J, Donnelly TM, eds. Clinical veterinary advisor: birds and exotic pets. St Louis: Elsevier Saunders, 2013.

  • 2. Morishita TY, Aye PP, Brooks DL. A survey of diseases of raptorial birds. J Avian Med Surg 1997; 11:7792.

  • 3. Thrall D. The canine and feline lung. In: Thrall D, ed. Textbook of veterinary diagnostic radiology. 6th ed. St Louis: Elsevier Saunders, 2013;608631.

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  • 4. Dahlhausen RD. Implications of mycosis in clinical disorders. In: Harrison GJ, Lightfoot T, eds. Clinical avian medicine. Palm Beach, Fla: Spix Publishing, 2006;691700.

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  • Figure 1—

    Right lateral (A) and ventrodorsal (B) radiographic views of the coelom of a young adult female bald eagle (Haliaeetus leucocephalus) evaluated because of lethargy and drooping wings. R = Right.

  • Figure 2—

    Same radiographic images as in Figure 1. Multiple pulmonary soft tissue nodules are seen within the lungs (arrows) and air sacs (black arrowhead). Thickening of the caudal thoracic air sac is evident as a conspicuous, curvilinear soft tissue opacity (asterisk). Gas is present within the area of the proventriculus and ventriculus (white arrowhead). See Figure 1 for remainder of key.

  • 1. Mayer J, Donnelly TM, eds. Clinical veterinary advisor: birds and exotic pets. St Louis: Elsevier Saunders, 2013.

  • 2. Morishita TY, Aye PP, Brooks DL. A survey of diseases of raptorial birds. J Avian Med Surg 1997; 11:7792.

  • 3. Thrall D. The canine and feline lung. In: Thrall D, ed. Textbook of veterinary diagnostic radiology. 6th ed. St Louis: Elsevier Saunders, 2013;608631.

    • Search Google Scholar
    • Export Citation
  • 4. Dahlhausen RD. Implications of mycosis in clinical disorders. In: Harrison GJ, Lightfoot T, eds. Clinical avian medicine. Palm Beach, Fla: Spix Publishing, 2006;691700.

    • Search Google Scholar
    • Export Citation

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