A Comparison of Hematological, Immunological, and Stress Responses to Capture and Transport in Wild White Rhinoceros Bulls (Ceratotherium simum simum) Supplemented With Azaperone or Midazolam

Abstract

Capture and transport are essential procedures for the management and conservation of southern white rhinoceroses (Ceratotherium simum simum), but are associated with stress-induced morbidity and mortality. To improve conservation efforts, it is crucial to understand the pathophysiology of rhinoceros stress responses and investigate drug combinations that could reduce these responses. In this study we measured rhinoceros stress responses to capture and transport by quantifying hematological and immunological changes together with adrenal hormone concentrations. We investigated whether the potent anxiolytic drug midazolam was able to mitigate these responses compared to azaperone, which is more commonly used during rhinoceros transport. Twenty three wild white rhinoceros bulls were transported for 6 h (280 km) within the Kruger National Park for reasons unrelated to this study. Rhinoceroses were immobilized with either etorphine-azaperone (group A, n = 11) or etorphine-midazolam (group M, n = 12) intramuscularly by darting from a helicopter. Azaperone (group A) or midazolam (group M) were re-administered intramuscularly every 2 h during transport. Serial blood samples were collected at capture (TC), the start of transport (T0) and after 6 h of transport (T6). Changes in hematological and immunological variables over time and between groups were compared using general mixed models. Increases in plasma epinephrine and serum cortisol concentrations indicated that rhinoceroses mounted a stress response to capture and transport. Packed cell volume decreased from TC to T6 indicating that stress hemoconcentration occurred at TC. Neutrophils progressively Pohlin et al.Translocation Stress in White Rhinoceroses increased and lymphocytes and eosinophils progressively decreased from T0 to T6, resulting in an increase in neutrophil to lymphocyte ratio; a characteristic leukocyte response to circulating glucocorticoids. A reduction in serum iron concentrations may suggest the mounting of an acute phase response. Rhinoceroses experienced a decrease in unsaturated fatty acids and an increase in lipid peroxidation products at capture and toward the end of transport indicating oxidative stress. Midazolam, at the dose used in this study, was not able to mitigate adrenal responses to stress and appeared to directly influence leukocyte responses.

Muscle tremors observed in white rhinoceroses immobilised with either etorphine–azaperone or etorphine–midazolam: An initial study

“…Midazolam, at the doses administered in this study, did not reduce muscle tremor scores in etorphine-immobilised rhinoceroses. Accordingly, midazolam failed to demonstrate a difference in circulating plasma epinephrine concentrations in the same rhinoceroses (Pohlin et al 2020b). The benzodiazepine acts on different receptors compared to etorphine and was, therefore, unable to directly mitigate any etorphine-induced tremors.…”

Arterial Blood Gases and Cardiorespiratory Parameters in Etorphine-Medetomidine-Midazolam Immobilized Free-Ranging and Game-Farmed Southern White Rhinoceroses (Ceratotherium simum simum) Undergoing Electro-Ejaculation

“…Rhinoceroses from Group 3 had a lower Hct compared to Group 2. An increased Hct is proposed to be associated with etorphine-induced catecholamine release ( 48 ). On the other hand, the higher glucose concentration in rhinoceroses of Group 3, is possibly related to a higher medetomidine dose, which has been shown to increase blood glucose concentrations in domestic animals ( 49 ).…”

Protein Electrophoresis and Haptoglobin Values for Captive Bongo (Tragelaphus eurycerus)

“…As this was a multi-institutional study utilizing samples collected over an approximately 15-year time span, there were differences in sample collection (including method of animal restraint, venipuncture location, and technique) and processing [sample preparation and varied implementation of FIB and complete blood cell (CBC) testing] that could potentially have influenced the results. To this point, stress-associated changes in hematological values and iron but not HP were reported in free-ranging white rhinoceros subject to transport with chemical immobilization ( 27 ). For the most part, HP is found to be stable with prolonged freezing ( 28 ).…”