A Fixed Moderate-dose Combination of Tiletamine+Zolazepam Outperforms Midazolam in Induction of Short-term Immobilization of Ball Pythons (Python regius)

Abstract

26 Laboratory animals are commonly anesthetized to prevent pain and distress and to provide safe 27 handling. Anesthesia procedures are well-developed for common laboratory mammals, but not as 28 well established in reptiles. We assessed the performance of intramuscularly injected tiletamine 29 (dissociative anesthetic) and zolazepam (benzodiazepine sedative) in fixed combination (2 mg/kg 30 and 3 mg/kg) in comparison to 2 mg/kg of midazolam (benzodiazepine sedative) in ball pythons 31 (Python regius). We measured heart and respiratory rates and quantified induction parameters 32 (i.e., time to loss of righting reflex, time to loss of withdrawal reflex) and recovery parameters 33 (i.e., time to regain righting reflex, withdrawal reflex, normal behavior). Mild decreases in heart 34 and respiratory rates (median decrease of <10 beats per minute and <5 breaths per minute) were 35 observed for most time points among all three anesthetic dose groups. No statistically significant 36 difference between the median time to loss of righting reflex was observed among animals of 37 any group (p = 0.783). However, the withdrawal reflex was lost in all snakes receiving 3mg/kg 38 of tiletamine+zolazepam but not in all animals of the other two groups (p = 0.0004). In addition, 39 the time for animals to regain the righting reflex and resume normal behavior was longer in the 40 drug combination dose groups compared to the midazolam group (p = 0.0055). Our results 41 indicate that midazolam is an adequate sedative for ball pythons but does not suffice to achieve 42 reliable immobilization or anesthesia, whereas tiletamine+zolazepam achieves short-term 43 anesthesia in a dose-dependent manner. Performance of Injectable Anesthetic Agents in Ball PythonsMiller et al. 4 INTRODUCTION45 A good understanding of the natural history, evolutionary development, and reproduction of 46 snakes (Reptilia: Squamata: Serpentes) is paramount for many reasons including conservation 47 efforts [1-4], evaluation of snake-specific sensory anatomy for chemoreception and behavior [5-48 8], and to help develop medical countermeasures against venomous snake bites, and finally the 49 development of candidate therapeutics for human health issues including clotting disorders and 50 cancer [9][10][11][12]. Snakes are also increasingly investigated as natural or accidental hosts for a 51 variety of viruses [13-23], and there is increased interest in snake fungal diseases such as those 52 caused by Ophidiomyces ophiodiicola [24] and the Chrysosporium anamorph of Nannizziopsis 53 vriesii complex (CANV) [25]. Snake researchers face unique challenges for husbandry, animal 54 restraint, biosample collection, and surgery. Varying levels of immobilization can be required 55 depending on the procedure to be performed, the size and temperament of the snakes, or their 56 ability to produce venom [26][27][28]. These challenges can be exacerbated when snakes are 57 suspected to be, or are infected with potentially zoonotic microorganisms or viruses, and when 58 the safety...