Ratite immobilizations are often precarious, as their powerful legs are used as a defense, and physical restraint may result in self-injury or injury to handlers. Although various combinations of opioids, alpha-2 adrenoreceptor agonists, and dissociatives have been employed in ratites, including a thiafentanil-medetomidine combination used in emus, few effective chemical immobilization protocols have been documented for rheas.1-3 In 2009, a novel cocktail consisting of 7.0 mg thiafentanil, 0.2 mg dexmedetomidine, and 100 mg Telazol was tested in eight adult (four male, four female) greater rheas (Rhea americana) at Wildlife Safari drive-through zoo. A Dan-Inject carbon dioxide powered pistol was used to deliver the drug combination into the thigh musculature, using a Type C Pneu-Dart with a gel collar and ¾” needle. Smooth inductions were observed with a mean time of 4.5 min to sternal recumbency. Atipamezole was administered to antagonize the cardiopulmonary depressant effects of the dexmedetomidine. Birds were intubated and maintained on isoflurane gas during clinical procedures. Naltrexone was administered to antagonize the thiafentanil, and midazolam was administered to smooth crate recoveries until release. Mean time to sternal recovery was 2.5 min. Respiratory depression was observed in one animal with evidence of respiratory acidosis on blood gas analysis; however, antagonists were administered, and the animal recovered without incident. This low volume, high potency, reversible drug combination demonstrated safe inductions, smooth recoveries, and proved to be a reliable anesthetic regime for greater rheas.
The authors would like to thank Oregon State University, Department of Biomedical Sciences for funding, as well as all of the veterinary students and Wildlife Safari staff who provided assistance with the study.
1. Cushing, A., and M. McClean (In press). 2010. Use of thiafentanil-medetomidine for the induction of anesthesia in emus (Dromaius novaehollandiae) within a wild animal park. J. Zoo Wildl. Med.
2. Lin, H., P.G. Todhunter, T.A. Powe, and D.C. Ruffin. 1997. Use of xylazine, butorphanol, tiletamine- zolazepam, and isoflurane for induction and maintenance of anesthesia in ratites. J. Am. Vet. Med. Assoc. 210: 244–248.
3. Siegal-Willott, J. 2007. Ratites. In: West, G., D. Heard, and N. Caulkett (eds.). Zoo Animal & Wildlife Immobilization and Anesthesia, 1st ed. Blackwell Publishing, Ames, Iowa. 325–334.