694 GLASSMAN AND BENNETT 



RESULTS AND DISCUSSION 



The size and composition of the cellular elements in normal, 

 uninfected animals were determined. Nucleated red blood cells 

 (RBC's) were characterized by size, number, and hemoglobin per 

 deciliter of whole blood (Table 1). No statistically significant changes 

 in red blood cell indexes, hemoglobin, or hematocrit were noted in 

 infected animals vs. wild or captively raised normals. White blood 



TABLE 1 



RED BLOOD CELL INDEXES FOR HEALTHY, UNINFECTED 



A lliga tor m ississipp iensis * 



Hemoglobin, 7.2 ± 0.4 g/dl 



Hematocrit, 19.9% ± 2.0 



Red blood cell count, 3.9 ± 0.07 X 10^ /mm^ 



Mean corpuscular volume, 522.0 ± 78 iJi^ 



Mean corpuscular hemoglobin, 190.0 ± 29.8 jJiJig 



Mean corpuscular hemoglobin concentration, 36.4% ± 2.2 



Red blood cell size (N = 65) 



Long axis, 17.2 ± 1.4 /i 



Short axis, 9.1 ± 1.2 jU 



*Values are x ± standard deviation. Sample size (N) = 8 unless 

 otherwise indicated. 



cells were categorized as: (1) granulocytes, (a) eosinophils, (b) 

 basophils; (2) neutrophilic macrophages; (3) lymphocytes; (4) 

 monocytoid cells; and (5) thrombocytes (Tables 2 and 3; Figs. 1 to 3). 



Infected animals had increased white blood cell counts, pre- 

 dominantly of the neutrophilic macrophage component. This is 

 consistent with the kind of host immune-defense mechanism seen in 

 higher vertebrates exposed to pyogenic organisms. Neutrophilic 

 macrophages increased from 37 to 70+% in the alligators infected 

 with A. hydrophila. Peroxidase staining, which is used in humans as 

 an aid in differentiating cells of the myelocytic systems from those of 

 the monocytic and lymphocyte series, demonstrated that the 

 neutrophilic macrophages were positive. They were also positive with 

 PAS stain, which detects glycogen. There was a high content of LAP 

 in the neutrophilic macrophages. 



Modes of exposure resulting in infection were contaminated 

 water in holding pens and injections. No infections were noted in 

 animals given A. hydrophila orally. Infected animals died most 

 frequently at 35°C and exhibited a diminished immune response, as 

 measured by ineffective increases of neutrophilic macrophages and 



