Morphologic and quantitative evaluation of bone marrow aspirates from Hispaniolan Amazon parrots (Amazona ventralis)

Background Bone marrow aspirate assessments provide valuable information about hematopoietic status and hematologic disease. Hematopoietic cell differentials and morphologies have been anecdotally described in psittacines, but quantitative studies are lacking. Objectives We aimed to determine differential cell counts and calculate granulocyte:erythroid (G:E) ratios in bone marrow aspirates from Hispaniolan Amazon parrots and report representative morphologies of the hematopoietic cells. Methods Bone marrow aspirates were collected from 32 clinically healthy, captive, parrots. Peripheral blood was obtained for CBCs. Bone marrow differential cell counts (%) were determined by counting 500 cells on modified Wright's-stained smears. G:E ratios were calculated. Representative images of hematopoietic cells at all stages of development were taken. Results Of the 32 parrots sampled, 17 bone marrow samples were of sufficient cellularity and quality for evaluation. Erythroid cells comprised 68.9 +/- 8.6% (total +/- SD) of the hematopoietic cells and consisted primarily of early- and late-stage polychromatophilic rubricytes (43.6 +/- 2.1% of total erythroid cells). Granulocytic cells comprised 28.1 +/- 3.8% of the hematopoietic cells and consisted primarily of mature and band heterophils (11.9 +/- 5.2% and 6.5 +/- 3.4%, respectively, of total granulocytic cells). A unique morphologic finding in avian progranulocytes was the presence of multiple different granules. The G:E ratio was 0.4 +/- 0.2 (median 0.4, range 0.1-0.9). Thrombocyte lineage cells could not be reliably identified and were not counted. CBC results were largely within expected limits. Conclusions The low G:E ratios observed could be normal in this species; however, these ratios could be affected by factors related to sampling and cell identification. These findings will be a valuable resource for the diagnostic evaluation of clinical bone marrow samples from Hispaniolan Amazon parrots and could serve as a general reference for psittacine bone marrow evaluation.