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

Authors

  • Mary Nasr Cornell University College of Veterinary Medicine
  • Leith C.R Meyer University of Pretoria
  • Peter Buss South African National Parks
  • Maria C Fàbregas University of Pretoria
  • Robin D Gleed Cornell University College of Veterinary Medicine
  • Jordyn M Boesch Cornell University College of Veterinary Medicine
  • Friederike Pohlin University of Pretoria

Abstract

Etorphine–azaperone is the most commonly used drug combination for chemical immobilisation of free-ranging white rhinoceroses, but causes several profound physiological disturbances, including muscle tremors. The addition of benzodiazepine sedatives, such as midazolam, has been proposed to reduce the muscular rigidity and tremors in immobilised rhinoceroses. Twenty-three free-ranging, sub-adult white rhinoceros bulls were darted and captured using a combination of etorphine plus either azaperone or midazolam. Skeletal muscle tremors were visually evaluated and scored by an experienced veterinarian, and
tremor scores and distance run were compared between groups using the Wilcoxon rank sum test. No statistical differences were observed in tremor scores (p = 0.435) or distance run (p = 0.711) between the two groups, and no correlation between these variables was detected (r = –0.628; p = 0.807). Etorphine–midazolam was as effective as etorphine–azaperone at immobilising rhinoceroses, with animals running similar distances. Although the addition of midazolam to the etorphine did not reduce tremor scores compared to azaperone, it might have other beneficial immobilising effects in rhinoceroses, and further investigation is
necessary to elucidate possible methods of reducing muscle tremoring during chemical immobilisation of rhinoceroses.
Keywords: white rhinoceros; muscle tremors; etorphine; midazolam; azaperone; immobilisation; muscle relaxation; butorphanol.

Author Biographies

Mary Nasr, Cornell University College of Veterinary Medicine

Oradell Animal Hospital, Paramus, New Jersey, United States of America and Section of Anaesthesiology
and Pain Medicine, Department of Clinical Sciences, Cornell University College of Veterinary Medicine, Ithaca, New York, United States of America

Leith C.R Meyer, University of Pretoria

Centre for Veterinary Wildlife Studies, Faculty of Veterinary Sciences, University of Pretoria, Onderstepoort, South Africa and Department of Paraclinical Sciences, Faculty of Veterinary Sciences, University of Pretoria,
Onderstepoort, South Africa

Peter Buss, South African National Parks

Veterinary Wildlife Services, Kruger National Park, South African National Parks, Skukuza, South Africa and Department of Production Animal Studies, Faculty of Veterinary Sciences, University of Pretoria, Onderstepoort, South Africa

Maria C Fàbregas, University of Pretoria

Centre for Veterinary Wildlife Studies, Faculty of Veterinary Sciences, University of Pretoria, Onderstepoort, South Africa and Department of Paraclinical Sciences, Faculty of Veterinary Sciences, University of Pretoria,
Onderstepoort, South Africa

Robin D Gleed, Cornell University College of Veterinary Medicine

Section of Anaesthesiology and Pain Medicine, Department of Clinical Sciences, Cornell University
College of Veterinary Medicine, Ithaca, New York, United States of America

Jordyn M Boesch, Cornell University College of Veterinary Medicine

Section of Anaesthesiology and Pain Medicine, Department of Clinical Sciences, Cornell University College of Veterinary Medicine, Ithaca, New York, United States of America

Friederike Pohlin, University of Pretoria

Centre for Veterinary Wildlife Studies, Faculty of Veterinary Sciences, University of Pretoria, Onderstepoort, South Africa and Department of Paraclinical Sciences, Faculty of Veterinary Sciences, University of Pretoria, Onderstepoort, South Africa and Research Institute of Wildlife Ecology, Department of Interdisciplinary Life Sciences, University of Veterinary Medicine, Vienna, Austria

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Published

2021-12-09

Issue

Section

Short Communications