Abstract
Tricaine methanesulfonate (MS-222) immersion is current standard of care for fish and anuran euthanasia,1 but research has proven it insufficient for euthanasia of goldfish.2 To assess appropriateness for humane euthanasia of anurans, this study evaluated the efficacy of three MS-222 euthanasia protocols in Smokey Jungle Frogs (SJF; Leptodactylus pentadactylus). Eighteen frogs (21–33 g) were exposed to one of three treatments via partial immersion: MS-222 at 2.5 g/L for 90 minutes (M2.5/90), 5 g/L for 60 minutes (M5/60), or 10 g/L for 60 minutes (M10/60). Physiologic parameters and times to loss of spontaneous movement and response to noxious stimuli (toe clamp) were recorded. Following exposure, frogs were rinsed with dechlorinated water and time to cessation of heart beat recorded. Survival in M2.5/90, M5/60, and M10/60 was 1/6, 0/6, and 0/6, respectively. In M2.5/90, 3/6 frogs had continued movement throughout exposure. In M5/60 and M10/60, median time to initial loss of movement was 14.3 (5.5–30.0) and 7.6 (4.8–19.7) minutes, respectively; however, 4/6 frogs in both groups demonstrated 1–3 episodes throughout exposure of regained consciousness and movement following loss of response to noxious stimuli. Median time to cessation of heart beat in M2.5/90, M5/60, and M10/60 was 90 (75–150), 105 (75–165), and 15 (15–150) minutes, respectively. Although death was achieved in 6/6 frogs exposed to 5 and 10 g/L, as the goal of euthanasia is a rapid and distress-free death,1 given the repeated events of regained consciousness, MS-222 immersion at ≤10 g/L is not an appropriate SJF euthanasia protocol.
Acknowledgements
The authors extend thanks to the veterinary and animal care staff at Brookfield Zoo for their support and assistance with this project.
* Presenting author
+ Student presenter
Literature Cited
1. AVMA Panel on Euthanasia. 2013. AVMA Guidelines for the Euthanasia of Animals: 2013 Edition. American Veterinary Medical Association; [accessed 2016 Dec 27]. www.avma.org/KB/Policies/Documents/euthanasia.pdf
2. Balko JA, Oda A, Posner LP. 2017. Immersion euthanasia of goldfish (Carassius auratus) using tricaine methanesulfonate (MS-222) or propofol. J Am Vet Med Assoc. (In press).