How to Read an Elephant Blood Film: A Valuable Diagnostic Tool in Sick Elephants (Elephas maximus, Loxodonta africana)
Although normal elephant hematology has been described,1 hemogram changes in disease are uncharacterized in the literature. Band heterophils in blood films of sick elephants, even in low percentages of 1 to 2%, seem to be significant indicators of systemic inflammation. Because band heterophils are observed with such diseases as elephant endotheliotropic herpesvirus (EEHV), salmonellosis, and surgical colics, their presence and morphology warrant further clinical investigation as diagnostic and prognostic indicators of disease. Observation of trends, such as relative increases and decreases in total numbers of lymphocytes and monocytes, as well as changes in the appearance of these cells, including reactivity and vacuolization, also have clinical relevance in the detection of systemic inflammation.
Elephant erythrocytes can show alterations in morphology, size and color in association with various inflammatory, infectious, and neoplastic diseases. Polychromasia and reticulocytes, not normally seen in blood films of healthy elephants, indicate a regenerative anemia. Platelets, normally abundant in elephant peripheral blood, can decrease dramatically with certain diseases, particularly EEHV. Since elephant platelets tend to clump in vitro, blood film evaluation is more likely to provide evidence of developing thrombocytopenia.
Appropriate sample handling and processing of elephant blood samples are essential for obtaining accurate results. A larger gauge needle, at least 18 gauge, is recommended to avoid hemolysis. This recommendation precludes the use of commercial ‘butterfly needles’ which are currently available at a maximum size of 19 gauge. Additionally, preparing a blood film immediately after phlebotomy can significantly improve blood sample quality and aid in its interpretation.
1. Harr K.E., R. Isaza, J.T. Blue. 2006. Hematology of elephants In: Weiss, D.J. and K.L. Wardrop, eds. Schalm's Veterinary Hematology. 6th ed. Ames, IA: Blackwell Publishing Ltd.; 2006:942–949.