Case Report
Severe Leukemoid Response Associated With Mycobacterium genavense Infection in a Pet Budgerigar (Melopsittacus undulatus)

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Abstract

A 2-year-old pet budgerigar was presented after a period of general malaise that was unresponsive to supportive therapy. Radiographic images revealed a marked hepatomegaly. Hematology results indicated the bird had a severe leukocytosis with marked discrepancy between the hemocytometer white blood cell (WBC) count and WBC estimated from the smear. The leukocytosis was characterized by an extreme heterophilia with marked left shift, including the presence of metamyelocytes and promyelocytes with marked toxic changes, and a marked monocytosis, consistent with a leukemoid response. The bird died despite supportive treatment. Hepatosplenomegaly was present at necropsy. Histopathology of multiple tissues demonstrated acid-fast organisms on Ziehl-Neelsen staining, subsequently identified as Mycobacterium genavese by polymerase chain reaction analysis. Mycobacteriosis should be considered as a differential diagnosis in the presence of a severe leukemoid response with multiple heterophilic precursors in avian species.

Section snippets

Case Report

A 2-year-old male budgerigar (46 g) was presented to Burwood Bird and Animal Hospital (Melbourne, Australia) for evaluation of lethargy, a reduced appetite, and dyspnea of 2 weeks’ duration. A fecal wet smear and Gram’s stain examination were performed showing scant bacteria, of which 90% were Gram-positive and 10% were Gram-negative cocci and rods. Candida albicans, Macrorhabdus ornithogaster, and gastrointestinal parasites were not detected. Blood (0.3 mL) was collected via right jugular

Discussion

Mycobacterial infections have been described in companion,1, 6, 7 zoo,8 and free-ranging9 birds, but the incidence is unclear.11, 12 In the USA, reviews of necropsy specimens have shown a prevalence of mycobacteriosis in avian species ranging between 0.5% and 14%,8, 10, 12 but the incidence of this avian disease within Australia has not been determined. It is estimated that there are around 4.8 million pet birds in Australia, with 13% of the Australian population owning at least one pet bird,13

Acknowledgments

The authors would like to thank Dr Janet Fyfe of the Mycobacterium Reference Laboratory, Melbourne for her assistance with the MGE sequencing; IDEXX Laboratories, Melbourne for initial examination of the hematology and serum biochemistry, and Dr John Jardine of Vetpath, Perth, for his interpretation of the histopathology associated with this case.

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