Atypical hemograms of the commercial duck

A description of standard and atypical heterophils, lymphocytes, and 2 types of giant cells found in the circulation of 17 wk commercial ducks (N = 24) in apparent good health is the subject. Heterophils were sorted as either "classic" (HC) having red rod-shaped cytoplasmic granules, "typical" (HT) having weakly stained granules providing a reticular cytoplasmic appearance, or rarely as "variant" types (HV) having orange spherical granules. Atypical HT's and HC's were in 14 of 24 (58%) of the ducks. Small lymphocytes (Ls), reactive lymphocytes and plasmacytes (Lm) were routinely found. Giant cells, also present, were placed with Lm or monocytes (Mn) depending on cytology. Two counts of 200 leukocytes gave the total white count (TWBC) and 2 heterophil/lymphocyte ratios. H/L 1 = (HT + HC +HV) / Ls; and H/L 2 = (HT + HC + HV) / (Ls + Lm). The results showed that TWBC were normal (~ 23,000 /μL) but both H/L ratios were highly variable. HT were differentiated from HC on nuclear and cytoplasmic criteria. Many HT and HC exhibited signs of deterioration. Some giant cells likely represented developmental stages. Multiple nucleoli were evident in others suggesting polyploidy. The more common lymphoid giants were usually round whereas monocyte types were irregular. Mn types were actively phagocytic often consuming thrombocytes or rarely erythrocytes (RBC). Giant cells of either type were in 13 of 24 (54%) of the duck hemograms. Conidiospores were detected in the blood smears of 4 ducks and bacteria in 2 with 1 duck having both. As all ducks were in apparent good health the blood born microorganisms likely represented low grade infections. Presumably the atypical cells were a response to the presence of toxins of bacterial and fungal origin. The presence of atypical heterophils and lymphocytes complicates interpretation of H/L ratios traditionally used to establish stress. As atypical cells can be found in the context of normal TWBC or nonstress H/L values cytological observations attain additional importance. Moreover, giant cells may be useful indicators of infection even without direct microscopic observation or isolation of the offending organisms.