News : 2017 : August

Case of the Month: Under the Microscope

In the new Case of the Month series, Dr. Nicole Stacy presents: Abnormal heterophil morphology and increased SAA concentrations in a cold-stunned Florida manatee during rehabilitation. In this case, an adult female Florida manatee was admitted to rehabilitation with lethargy and focal cold stress lesions in early February after a cold snap event in South Florida.

Initial CBC and chemistry abnormalities (refs1,2):

  • Marked mature heterophilia with marked left-shift and toxicity (2+ to 3+/all on a 3+ grading scale, ref 3)
  • WBC count 28.5 K/ul [RI 2.77-15.5 K/ul]; heterophils 21.2 [RI 0.77-6.53/K/ul]; band heterophils 3.4 K/ul [RI 0-0.22 K/ul]; metamyelocytes 1.2 K/ul and myelocytes 0.8 K/ul [RI 0]
  • Mild monocytosis: 2.9 K/ul [RI 0.08-1.70 K/ul]
  • Mild nonregenerative anemia: PCV 27% [RI 29-44%]
  • Moderately increased CK: 7540 U/L [RI 51-2966 U/L]
  • Moderate hyperkalemia: 8.1 mmol/L [RI 3.8-6.3 mmol/L]
  • Markedly increased SAA: 1,218 mg/L [RI 0-46 mg/L] (ref 4)

Blood film from a cold-stressed manatee at time of rehabilitation with left-shifted and toxic heterophils. Insert: normal heterophil for comparison. Wright-Giemsa stain

Blood film from a cold-stressed manatee at time of rehabilitation with left-shifted and toxic heterophils. Insert: normal heterophil for comparison. Wright-Giemsa stain.

The hemogram findings were consistent with chronic-active inflammation and mild nonregenerative anemia. The high SAA level supported the diagnosis of inflammation. The concurrent increases in CK and K were most consistent with muscle damage (e.g., from exertion and/or impaired blood flow from hyopthermia). A metabolic acidosis component may have contributed to the increased K; however, blood gas analysis was not available at the time of admission to further assess the acid base status. Although CBC and chemistry abnormalities normalized by week 6 into rehabilitation, the SAA continued to be increased until week 12:

Day 0: 1,218 mg/L
Day 32: 917 mg/L
Day 44: 985 mg/L
Day 62: 483 mg/L
Day 72: 144 mg/L
Day 86: 37 mg/L
Day 98: 39 mg/L

After 4 months of rehabilitation, the patient had fully recovered clinically, supported by CBC, chemistry, and SAA that were within normal limits, and was released.
Toxicity in heterophils (or neutrophils in other species) is a morphologic change that develops in the bone marrow during conditions with intense heterophil (neutrophil) production and shortened maturation time such as that present during inflammation (ref 3). In this case, SAA was increased for longer than the time to disappearance of heterophil toxicity. Although the disappearance of toxicity is considered a good prognostic indicator, SAA has much higher sensitivity and specificity than other blood analytes investigated in manatees for diagnosis and monitoring of systemic inflammation (refs 4,5).

References

1. Harvey, J.W., Harr, K.E., Murphy, D., Walsh, M.T., Nolan, E.C., Bonde, R.K., Pate, M.G., Deutsch, C.J., Edwards, H.H. and Clapp, W.L., 2009. Hematology of healthy Florida manatees (Trichechus manatus). Veterinary Clinical Pathology, 38(2), pp.183-193.

2. Harvey, J.W., Harr, K.E., Murphy, D., Walsh, M.T., Chittick, E.J., Bonde, R.K., Pate, M.G., Deutsch, C.J., Edwards, H.H. and Haubold, E.M., 2007. Clinical biochemistry in healthy manatees (Trichechus manatus latirostris). Journal of Zoo and Wildlife Medicine, 38(2), pp.269-279.

3. Harvey, J.W., 2011. Veterinary Hematology: A Diagnostic Guide and Color Atlas. Elsevier Health Sciences.

4. Cray, C., Rodriguez, M., Dickey, M., Brewer, L.B. and Arheart, K.L., 2013. Assessement of serum amyloid A levels in the rehabilitation setting in the Florida manatee (Trichechus manatus latirostris). Journal of Zoo and Wildlife Medicine, 44(4), pp.911-917.

5. Harr, K., Harvey, J., Bonde, R., Murphy, D., Lowe, M., Menchaca, M., Haubold, E. and Francis-Floyd, R., 2006. Comparison of methods used to diagnose generalized inflammatory disease in manatees (Trichechus manatus latirostris). Journal of Zoo and Wildlife Medicine, 37(2), pp.151-159.

Manatee image kindly provided by the U.S. Geological Survey – Sirenia Project