The clinician should always carefully review the differential and cell morphology to determine if illness seems likely. Our experience, young birds residing in pet stores before sale to the public, tend to run higher leukocyte counts in the absence of documentable disease. Disease-caused leukocytosis in birds occurs mostly due to infections. Degenerative and neoplastic disorders can inconsistently present with moderate elevations in the total leukocyte counts. The clinician cannot easily differentiate diseases based solely on leukocytosis, but certain trends emerge.
Mild leukocytosis correlates with bacterial, fungal, and chlamydial infections.
Moderate elevations can be caused by yolk peritonitis, granulomatous disease, and some phases of septicemia. Of course these counts are rated differently in various species. Leukemia must be included in the differential diagnosis of very high leukocyte counts, but cannot be easily ruled out without repeated morphologic examination of peripheral and bone marrow elements. Leukopenia Leukopenia must be interpreted in conjunction with knowledge of typical reference ranges for the species examined. Smaller birds tend to have lower normal leukocyte counts.