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Clinical Technique: Handling and Treating Venomous Snakes
Topics in Medicine and Surgery
Clinical Technique: Handling and Treating Venomous Snakes Robert Johnson, BVSc, MACVSc, CertZooMed, BA
Abstract This article describes safe handling techniques for venomous snakes in the consulting room. Practical information is presented for clinicians who treat venomous snakes to reduce the risk of injury to the handler as well as the animal being treated. © 2011 Published by Elsevier Inc. Key words: elapid; heading; tubing; venomoid; venomous
V
eterinarians who treat reptiles, and in particular snakes, will be asked to examine venomous snakes. It is important for clinicians to first determine if they want to treat venomous snakes. If the answer is yes, start with a thorough education that includes venomous snake identification, safe capture, and handling practices in the consulting room. The educational process also includes learning about the proper equipment needed for optimum safety and protection of both the handler and patient. The required equipment must be available before the first venomous snake is presented to the clinic. The author practices in Australia and sees Australian venomous species (most of which are elapids) in his veterinary hospital. Basic principles for the handling of venomous snakes are similar for all venomous snake families, requiring the same high standard of care, knowledge of ophidian behavior, and attention to detail. The focus of this article will be safe handling and examination of venomous snakes with an emphasis on elapids. Taxonomy, venomous snake identification, and emergency protocols for the treatment of snake bite are well covered in the literature.1-4 Readers should note that the treatment of a snake bite, particularly the administration of first aid, varies depending on the species of snake involved with the injury.
124
Common Species Venomous snakes are frequently classified into 3 groups based on their dentition: proteroglyphs, solenoglyphs, and opisthoglyphs. Aglyphous snakes are not venomous and do not have fangs (e.g., pythons).
Proteroglyphs Proteroglyphous snakes (elapids) are characterized in part by a complex venom production and delivery system.5 The system consists of a large venom gland in the temporal region of the head connected by a duct to the base of a large syringe-like fang on the rostral end of the maxilla. Because the entire venom production and delivery system is enclosed, except for the small opening at the tip of the fang, the secretion can be delivered quickly and under pressure when the snake bites. The word proteroglyph From the South Penrith Veterinary Clinic, Penrith, NSW, Australia. Address correspondence to: Robert Johnson, BVSc, MACVSc, CertZooMed, BA, South Penrith Veterinary Clinic 126 Stafford Street, Penrith, NSW, Australia 2750. E-mail: clinic@reptilevet. com.au. © 2011 Published by Elsevier Inc. 1557-5063/11/2002-$30.00 doi:10.1053/j.jepm.2011.02.007
Journal of Exotic Pet Medicine, Vol 20, No 2 (April), 2011: pp 124 –130
125
Handling and Treating Venomous Snakes
(Greek) refers to the rostral position of the fang in relation to the other maxillary teeth.
Solenoglyphs Solenoglyphous snakes include vipers and pit vipers, which have large, mobile fangs that fold caudally along the upper jaw when not in use.6
Handling Venomous snakes should be skillfully restrained for the physical examination, preferably by the keeper or owner and not the veterinarian. It is recommended that only experienced reptile veterinarians examine and treat venomous species.
Equipment Opisthoglyphs Opisthoglyphous snakes comprise several groups of colubrid snakes (e.g., brown tree snake, Boiga irregularis) that have enlarged fangs at the rear of the mouth.
Elapids and Envenomation The Fang “Fang, n. 1, any long, sharp, pointed tooth with which prey is seized and held. 2, a tooth in the upper jaw which is recurved, conical, and elongate, and contains a lumen running along the anterior margin with orifices near the base and slightly proximally from the tip, through which the venom passes.”7
Elapidae The elapids, belonging to the proteroglyph group of snakes, are the largest family of snakes in Australia. 5 There are 75 recognized species of elapidae compared with the other 92 species in the other 7 families of Australian snakes. Elapid fangs have an enclosed venom duct that opens in proximity to the distal tip. The main venom glands are modified parotid glands situated on each side of the head behind and below the eye that extend caudally beyond the corner of the mouth. These exocrine venom glands are enveloped by a fibrous capsule from which the fibers of the mandibular muscle arise.1 When an elapid snake prepares to strike, the fangs rotate in a rostral direction; this allows for a more vertical strike as the fang enters the skin of the victim. The degree of rotation is much more pronounced in solenoglyphous snakes (e.g., vipers) because of the length of their fangs. The muscle surrounding the venom gland contracts as the fang enters the skin, forcing the venom out of the opening of the venom duct at the proximal distal tip of the fang similar to a hypodermic injection. Except for the genus Pseudonaja, which strikes with an open mouth, Australian snakes insert their fangs into the skin of the victim with their mouth closed.
Equipment required for the safe handling of venomous snakes includes the following: jiggers, hooks, pinning sticks, hoop bags with sewn corners, clear plastic tubes, pads (foam rubber), secure containers and holding facilities.2
“Tubing” Tubing is a safer and less stressful snake capture technique for both the patient and handler compared with tailing, pinning, and heading. Clear plastic tubes are selected based on the size and length of the snake. The snake is initially coaxed into the tube (Fig 1), and once the snake has entered the tube with a significant percentage of the body, the body and the tube are grasped firmly together to prevent escape (Fig 2). A snug-fitting tube will prevent the snake from turning around. Snakes may become “tube shy” after repeated use of this handling technique. For the “tube shy” snakes it is recommended that the end of the tube be marked or painted in a dark color to encourage the snake to enter. Certain snake groups such as crotalids (e.g., rattlesnakes) and vipers exhibit different behaviors and
Figure 1. Tubing a mainland tiger snake, Notechis scutatus.
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Johnson
Figure 4. Intubated mainland tiger snake, Notechis scutatus. Figure 2. Securing snake and tube for examination.
can be more difficult to coax into a tube compared with elapids.
“Heading” of Snakes “Heading,” which is pinning and manually restraining the head of a snake, should only be performed for close examination of the cranial portion of the snake (Fig 3), procedures such as tracheal intubation (Fig 4), and stomach tubing (Fig 5). A special “pinning” jigger and a soft surface (e.g., folded towel, piece of thick rubber foam padding) are required to firmly hold the
Figure 3. Restraining the head of a mulga snake, Pseudechis australis.
head (Fig 6). The head is then carefully restrained with the thumb and middle finger on either side of the head and the index finger on top, taking care to avoid contact with the fangs. Juvenile and smaller venomous snakes such as the yellow-faced whip snake, Demansia psammophis, may move very quickly and prove difficult to restrain and treat. It is often best to determine the position of the snake while it is still in the bag and to apply gentle, firm pressure on the head from the outside. This technique is only recommended for the less dangerous snakes. Once restrained, the free hand is used to control the snake from inside the bag. It can then be safely removed for inspection. Juvenile venomous snakes can also be problematic to handle and treat (Fig 7).
Figure 5. Stomach tubing a broad-headed snake, Hoplocephalus bungaroides.
127
Handling and Treating Venomous Snakes
Figure 8. Handling a common death adder, Acanthophis antarcticus, with a hook and tongs.
ability to turn and strike the handler with ease. Instead they should only be handled with a hook and tongs (Fig 8).
Figure 6. Pinning and heading a mainland tiger snake, Notechis scutatus.
“Tailing” Handling snakes by the tip of the tail to examine them and/or “head” or “tube” them for capture should only be done by experts. Death adders (Acanthophis antarcticus) should never be tailed because of their short, plump body and an innate
Safety Preparing for the Examination Veterinarians treating venomous snakes must know the experience and competence of the person handling the animal. Most of the experienced competent snake handlers who work with venomous animals are zookeepers, experienced wildlife rescuers, and occasionally private herpetologists. The examination room must be escape proof, with all gaps under doors and cabinets blocked off. Ensure that snakes cannot wedge themselves under large items of furniture, such as refrigerators, desks, and weighing scales. All unessential personnel and onlookers should be excluded from the examination room. All people within the building should be informed that a venomous snake is being examined and a large, easily recognized sign should be posted on the examination room door. First aid knowledge is mandatory for keepers and owners of venomous snakes. In the rare event of a snake bite, bandages should be available for applying first aid. Guarantee that the local hospital has antivenom available for the common species that are presented to the hospital.
Legal Issues for Consideration Figure 7. Juvenile common brown snake, Pseudonaja textilis, attached to adhesive tape. Such small snakes require gentle and cautious handling.
●
Legal responsibilities of the veterinarian should be considered when handling venomous snakes.8
128
Johnson
must be removed from the tube. One must take extreme care when grasping the head of the snake as the animal retreats from the tube. It is often easier and safer to completely remove the snake from the tube by allowing it to either move in a forward direction and be placed in the holding bin or slide out in a backward direction. The snake should then be pinned for the oral cavity examination. Snakes should remain in the tube for ultrasound examination, radiographic examination, probing, and blood sampling.
Diagnostics Figure 9. Typical appearance of a pre-ecdysis spectacle in the coastal taipan, Oxyuranus scutellatus, as viewed through a snake tube.
●
Who is responsible in the event of a bite: rescuer, handler, staff, or the veterinarian?
●
Do veterinary hospitals have protocols for the handling of venomous snakes?
●
Have you informed your insurer that you handle venomous snakes?
●
Understand the legal and licensing issues of owning or keeping exotic venomous reptiles in private collections.
Blood Collection As with most snake patients, blood is collected from the ventral coccygeal vein. Collection by cardiac puncture is also possible; however, this technique is best performed with the snake under anesthesia (the heart is more easily visualized in an anesthetized snake). The position of the heart within the body
Venomoid Snakes Venomoid snakes are snakes that have undergone surgery to section the venom duct or ablate the venom gland.2,8 This practice is viewed by most reptile veterinarians and herpetologists as disfiguring surgery and considered by some as professional malpractice. Venomoid snakes can never be guaranteed as “de-venomed.” The surgery may be incomplete or incorrectly performed (often by nonveterinarians). It is apparent that there are considerable legal and liability issues associated with this practice. In addition, there is the subsequent risk of people being bitten by apparently venomoid snakes that still have remnants of venom gland tissue and/or patent venom ducts. Venomoid snakes should always be regarded as venomous.
Clinical Examination Once a snake is “tubed,” a physical examination can be conducted. The skin, eyes, and cloaca can be examined safely while the snake is restrained (Fig 9). To adequately examine the oral cavity the snake
Figure 10. Cardiac puncture in a sedated and restrained red-bellied black snake, Pseudechis porphyriacus.
129
Handling and Treating Venomous Snakes
Inhalation Anesthesia and Intubation (Isoflurane and Oxygen). A risk/benefit analysis of the need to “head” the snake should be determined by the veterinarian. Inhalation anesthesia is required for procedures lasting longer than 10 minutes.
Monitoring. Observe the heartbeat directly or use a Doppler monitor. Recovery. ●
Place the snake in a secure hospital cage or container while still anesthetized.
●
Ensure that the snake is visible to enable postanesthetic monitoring.
●
See notes on hospitalization.
Figure 11. Modified anesthetic mask fitted to the snake tube.
cavity varies depending on the species of snake from which the blood is being collected. In Australian elapids, the heart is situated 20% to 24% of the snout vent length.9 Cardiocentesis is facilitated if the snake is placed in dorsal recumbency and the position of the heart stabilized between 2 fingers (Fig 10). Studies have shown that serial cardiocentesis is well tolerated in some snakes.10
Treatments Consider treatment options carefully: ●
Does the snake even need to be handled?
●
Minimize the number of handlers. Often the veterinarian does not have to handle the snake.
●
Should the snake be anesthetized?
Injection sites and techniques are similar to those used in nonvenomous species.
●
Injury site
●
Near the head—is “heading” required?
Microchipping
●
Caudal body—“tubing” will suffice.
Microchipping sites are similar to those used in nonvenomous species.
●
Use absorbable sutures to reduce postsurgical handling.
●
Treat the snake as an outpatient if possible.
Injection Sites
Anesthesia To avoid double handling, venomous snakes are often not premedicated. Anesthetic induction may be initiated by fitting a modified mask to the end of the tube holding the snake (Fig 11). Great care is required when removing the snake from the tube for intubation. An alternative method for anesthetic induction is to “head” the snake, intubate it while conscious, and immediately begin ventilating the patient. The author’s method of choice is to induce anesthesia by administering alfaxalone (5-8 mg/kg, intravenous, Alfaxan-CD RTU; Jurox, Rutherford, NSW, Australia) in the ventral coccygeal vein while the snake is restrained in a tube. After the injection, return the snake to the holding container and intubate once sedated. The selection of an anesthetic protocol will depend on the species of snake, site, and extent of injury or body region to be examined.
Figure 12. A locked and labeled hospital cage suitable for a venomous snake.
130
Johnson
minimize the chance of envenomation, it is often safer to decapitate the dead snake and place the head directly into a jar that contains decalcifying formalin solution.
Carcass Disposal Sever the head from the body and place it in a firm, sealable, and crushproof container (e.g., plastic jar or tub).
Disclaimer
Figure 13. Injection of intracardiac pentobarbitone in a coastal taipan, Oxyuranus scutellatus.
●
If it is still eating, medicate the snake via a food item.
If injectable medication is the only treatment option, choose a drug that requires a lower frequency of administration (e.g., ceftazidime every 72 hours, intramuscular, Fortaz; GlaxoSmithKline, Philadelphia, PA USA).
Hospitalization It is preferable to treat venomous snakes as outpatients. If hospitalization is required, ensure that a locked, labeled enclosure is available in a secure room (Fig 12). Access to the secure room that contains the venomous snake(s) should be restricted to authorized staff only. Snake hooks, jiggers, and tubes should be easily accessible outside and within the secure room.
Veterinarians treat venomous snakes at their own discretion and should be acutely aware of the risks involved. These notes are meant as a guide only. The advice contained within this article may change with time as new, safer equipment and techniques evolve. Veterinarians are advised to familiarize themselves with snake identification and make their own enquiries relating to specific species and procedural concerns.
References 1.
2. 3.
4. 5.
Euthanasia As for many animals, a 2-stage euthanasia technique is recommended for venomous snakes. The euthanasia solution (Beuthanasia-D; Schering Plough Animal Health, New York, NY USA) is administered using the ventral coccygeal vein in a previously sedated or anesthetized snake. Cardiocentesis may be necessary if venous access is difficult or not possible (Fig 13).
6. 7. 8.
Necropsy 9.
Equipment. Protective eyewear and gloves should be worn when handling dead snakes because envenomation may still occur from a dead animal. Care should be taken when dissecting the venom gland, and this structure should be avoided if necessary. To
10.
Sutherland SK: Appendix— key to the identification of Australian snakes, in Sutherland SK (ed): Australian Animal Toxins. Melbourne, Australia, Oxford University Press, pp 33-39, 1983 Boyer TH: Common procedures with venomous reptiles. Vet Clin North Am Exotic Anim Pract 9:269285, 2006 Whitaker BR, Gold BS: Working with venomous species: emergency protocols, in Mader DR (ed): Reptile Medicine and Surgery (ed 2). St. Louis, MO, Saunders/Elsevier, pp 1051-1061, 2006 Shea GM: The distribution and identification of dangerously venomous Australian terrestrial snakes. Aust Vet J 12:791-798, 1999 Greer A: Elapidae—venomous land snakes, in Greer A (ed): The Biology and Evolution of Australian Snakes. Chipping Norton, Australia, Surrey Beatty and Sons, pp 132-246, 1997 Shine R: Anatomy of a snake, in Shine R (ed): Australian Snakes: A Natural History. Chatswood, Australia, Reed Publishing, pp 8-27, 1991 Peters JA: Dictionary of Herpetology. New York, NY, Hafner Publishing Co., 1964 Johnson RSP: What snake is that? Proceedings of the Combined Conference of the Association of Avian Veterinarians Australasian Committee and the Unusual and Exotic Pets Veterinarians, Australian Veterinary Association, Hobart, Tasmania, Australia, pp 225-230, 2010 McCracken H: Organ location in snakes for diagnostic and surgical evaluation, in Fowler ME, Miller RE (eds): Zoo and Wildlife Animal Medicine, Current Therapy 4. Philadelphia, PA, WB Saunders, pp 243-248, 1999 Isaza R, Andrews G, Coke R, et al: Assessment of multiple cardiocentesis in ball pythons (Python regius). Contemp Top Lab Anim Sci 43(6):35-38, 2004
Clinical Technique: Handling and Treating Venomous Snakes Robert Johnson, BVSc, MACVSc, CertZooMed, BA
Abstract This article describes safe handling techniques for venomous snakes in the consulting room. Practical information is presented for clinicians who treat venomous snakes to reduce the risk of injury to the handler as well as the animal being treated. © 2011 Published by Elsevier Inc. Key words: elapid; heading; tubing; venomoid; venomous
V
eterinarians who treat reptiles, and in particular snakes, will be asked to examine venomous snakes. It is important for clinicians to first determine if they want to treat venomous snakes. If the answer is yes, start with a thorough education that includes venomous snake identification, safe capture, and handling practices in the consulting room. The educational process also includes learning about the proper equipment needed for optimum safety and protection of both the handler and patient. The required equipment must be available before the first venomous snake is presented to the clinic. The author practices in Australia and sees Australian venomous species (most of which are elapids) in his veterinary hospital. Basic principles for the handling of venomous snakes are similar for all venomous snake families, requiring the same high standard of care, knowledge of ophidian behavior, and attention to detail. The focus of this article will be safe handling and examination of venomous snakes with an emphasis on elapids. Taxonomy, venomous snake identification, and emergency protocols for the treatment of snake bite are well covered in the literature.1-4 Readers should note that the treatment of a snake bite, particularly the administration of first aid, varies depending on the species of snake involved with the injury.
124
Common Species Venomous snakes are frequently classified into 3 groups based on their dentition: proteroglyphs, solenoglyphs, and opisthoglyphs. Aglyphous snakes are not venomous and do not have fangs (e.g., pythons).
Proteroglyphs Proteroglyphous snakes (elapids) are characterized in part by a complex venom production and delivery system.5 The system consists of a large venom gland in the temporal region of the head connected by a duct to the base of a large syringe-like fang on the rostral end of the maxilla. Because the entire venom production and delivery system is enclosed, except for the small opening at the tip of the fang, the secretion can be delivered quickly and under pressure when the snake bites. The word proteroglyph From the South Penrith Veterinary Clinic, Penrith, NSW, Australia. Address correspondence to: Robert Johnson, BVSc, MACVSc, CertZooMed, BA, South Penrith Veterinary Clinic 126 Stafford Street, Penrith, NSW, Australia 2750. E-mail: clinic@reptilevet. com.au. © 2011 Published by Elsevier Inc. 1557-5063/11/2002-$30.00 doi:10.1053/j.jepm.2011.02.007
Journal of Exotic Pet Medicine, Vol 20, No 2 (April), 2011: pp 124 –130
125
Handling and Treating Venomous Snakes
(Greek) refers to the rostral position of the fang in relation to the other maxillary teeth.
Solenoglyphs Solenoglyphous snakes include vipers and pit vipers, which have large, mobile fangs that fold caudally along the upper jaw when not in use.6
Handling Venomous snakes should be skillfully restrained for the physical examination, preferably by the keeper or owner and not the veterinarian. It is recommended that only experienced reptile veterinarians examine and treat venomous species.
Equipment Opisthoglyphs Opisthoglyphous snakes comprise several groups of colubrid snakes (e.g., brown tree snake, Boiga irregularis) that have enlarged fangs at the rear of the mouth.
Elapids and Envenomation The Fang “Fang, n. 1, any long, sharp, pointed tooth with which prey is seized and held. 2, a tooth in the upper jaw which is recurved, conical, and elongate, and contains a lumen running along the anterior margin with orifices near the base and slightly proximally from the tip, through which the venom passes.”7
Elapidae The elapids, belonging to the proteroglyph group of snakes, are the largest family of snakes in Australia. 5 There are 75 recognized species of elapidae compared with the other 92 species in the other 7 families of Australian snakes. Elapid fangs have an enclosed venom duct that opens in proximity to the distal tip. The main venom glands are modified parotid glands situated on each side of the head behind and below the eye that extend caudally beyond the corner of the mouth. These exocrine venom glands are enveloped by a fibrous capsule from which the fibers of the mandibular muscle arise.1 When an elapid snake prepares to strike, the fangs rotate in a rostral direction; this allows for a more vertical strike as the fang enters the skin of the victim. The degree of rotation is much more pronounced in solenoglyphous snakes (e.g., vipers) because of the length of their fangs. The muscle surrounding the venom gland contracts as the fang enters the skin, forcing the venom out of the opening of the venom duct at the proximal distal tip of the fang similar to a hypodermic injection. Except for the genus Pseudonaja, which strikes with an open mouth, Australian snakes insert their fangs into the skin of the victim with their mouth closed.
Equipment required for the safe handling of venomous snakes includes the following: jiggers, hooks, pinning sticks, hoop bags with sewn corners, clear plastic tubes, pads (foam rubber), secure containers and holding facilities.2
“Tubing” Tubing is a safer and less stressful snake capture technique for both the patient and handler compared with tailing, pinning, and heading. Clear plastic tubes are selected based on the size and length of the snake. The snake is initially coaxed into the tube (Fig 1), and once the snake has entered the tube with a significant percentage of the body, the body and the tube are grasped firmly together to prevent escape (Fig 2). A snug-fitting tube will prevent the snake from turning around. Snakes may become “tube shy” after repeated use of this handling technique. For the “tube shy” snakes it is recommended that the end of the tube be marked or painted in a dark color to encourage the snake to enter. Certain snake groups such as crotalids (e.g., rattlesnakes) and vipers exhibit different behaviors and
Figure 1. Tubing a mainland tiger snake, Notechis scutatus.
126
Johnson
Figure 4. Intubated mainland tiger snake, Notechis scutatus. Figure 2. Securing snake and tube for examination.
can be more difficult to coax into a tube compared with elapids.
“Heading” of Snakes “Heading,” which is pinning and manually restraining the head of a snake, should only be performed for close examination of the cranial portion of the snake (Fig 3), procedures such as tracheal intubation (Fig 4), and stomach tubing (Fig 5). A special “pinning” jigger and a soft surface (e.g., folded towel, piece of thick rubber foam padding) are required to firmly hold the
Figure 3. Restraining the head of a mulga snake, Pseudechis australis.
head (Fig 6). The head is then carefully restrained with the thumb and middle finger on either side of the head and the index finger on top, taking care to avoid contact with the fangs. Juvenile and smaller venomous snakes such as the yellow-faced whip snake, Demansia psammophis, may move very quickly and prove difficult to restrain and treat. It is often best to determine the position of the snake while it is still in the bag and to apply gentle, firm pressure on the head from the outside. This technique is only recommended for the less dangerous snakes. Once restrained, the free hand is used to control the snake from inside the bag. It can then be safely removed for inspection. Juvenile venomous snakes can also be problematic to handle and treat (Fig 7).
Figure 5. Stomach tubing a broad-headed snake, Hoplocephalus bungaroides.
127
Handling and Treating Venomous Snakes
Figure 8. Handling a common death adder, Acanthophis antarcticus, with a hook and tongs.
ability to turn and strike the handler with ease. Instead they should only be handled with a hook and tongs (Fig 8).
Figure 6. Pinning and heading a mainland tiger snake, Notechis scutatus.
“Tailing” Handling snakes by the tip of the tail to examine them and/or “head” or “tube” them for capture should only be done by experts. Death adders (Acanthophis antarcticus) should never be tailed because of their short, plump body and an innate
Safety Preparing for the Examination Veterinarians treating venomous snakes must know the experience and competence of the person handling the animal. Most of the experienced competent snake handlers who work with venomous animals are zookeepers, experienced wildlife rescuers, and occasionally private herpetologists. The examination room must be escape proof, with all gaps under doors and cabinets blocked off. Ensure that snakes cannot wedge themselves under large items of furniture, such as refrigerators, desks, and weighing scales. All unessential personnel and onlookers should be excluded from the examination room. All people within the building should be informed that a venomous snake is being examined and a large, easily recognized sign should be posted on the examination room door. First aid knowledge is mandatory for keepers and owners of venomous snakes. In the rare event of a snake bite, bandages should be available for applying first aid. Guarantee that the local hospital has antivenom available for the common species that are presented to the hospital.
Legal Issues for Consideration Figure 7. Juvenile common brown snake, Pseudonaja textilis, attached to adhesive tape. Such small snakes require gentle and cautious handling.
●
Legal responsibilities of the veterinarian should be considered when handling venomous snakes.8
128
Johnson
must be removed from the tube. One must take extreme care when grasping the head of the snake as the animal retreats from the tube. It is often easier and safer to completely remove the snake from the tube by allowing it to either move in a forward direction and be placed in the holding bin or slide out in a backward direction. The snake should then be pinned for the oral cavity examination. Snakes should remain in the tube for ultrasound examination, radiographic examination, probing, and blood sampling.
Diagnostics Figure 9. Typical appearance of a pre-ecdysis spectacle in the coastal taipan, Oxyuranus scutellatus, as viewed through a snake tube.
●
Who is responsible in the event of a bite: rescuer, handler, staff, or the veterinarian?
●
Do veterinary hospitals have protocols for the handling of venomous snakes?
●
Have you informed your insurer that you handle venomous snakes?
●
Understand the legal and licensing issues of owning or keeping exotic venomous reptiles in private collections.
Blood Collection As with most snake patients, blood is collected from the ventral coccygeal vein. Collection by cardiac puncture is also possible; however, this technique is best performed with the snake under anesthesia (the heart is more easily visualized in an anesthetized snake). The position of the heart within the body
Venomoid Snakes Venomoid snakes are snakes that have undergone surgery to section the venom duct or ablate the venom gland.2,8 This practice is viewed by most reptile veterinarians and herpetologists as disfiguring surgery and considered by some as professional malpractice. Venomoid snakes can never be guaranteed as “de-venomed.” The surgery may be incomplete or incorrectly performed (often by nonveterinarians). It is apparent that there are considerable legal and liability issues associated with this practice. In addition, there is the subsequent risk of people being bitten by apparently venomoid snakes that still have remnants of venom gland tissue and/or patent venom ducts. Venomoid snakes should always be regarded as venomous.
Clinical Examination Once a snake is “tubed,” a physical examination can be conducted. The skin, eyes, and cloaca can be examined safely while the snake is restrained (Fig 9). To adequately examine the oral cavity the snake
Figure 10. Cardiac puncture in a sedated and restrained red-bellied black snake, Pseudechis porphyriacus.
129
Handling and Treating Venomous Snakes
Inhalation Anesthesia and Intubation (Isoflurane and Oxygen). A risk/benefit analysis of the need to “head” the snake should be determined by the veterinarian. Inhalation anesthesia is required for procedures lasting longer than 10 minutes.
Monitoring. Observe the heartbeat directly or use a Doppler monitor. Recovery. ●
Place the snake in a secure hospital cage or container while still anesthetized.
●
Ensure that the snake is visible to enable postanesthetic monitoring.
●
See notes on hospitalization.
Figure 11. Modified anesthetic mask fitted to the snake tube.
cavity varies depending on the species of snake from which the blood is being collected. In Australian elapids, the heart is situated 20% to 24% of the snout vent length.9 Cardiocentesis is facilitated if the snake is placed in dorsal recumbency and the position of the heart stabilized between 2 fingers (Fig 10). Studies have shown that serial cardiocentesis is well tolerated in some snakes.10
Treatments Consider treatment options carefully: ●
Does the snake even need to be handled?
●
Minimize the number of handlers. Often the veterinarian does not have to handle the snake.
●
Should the snake be anesthetized?
Injection sites and techniques are similar to those used in nonvenomous species.
●
Injury site
●
Near the head—is “heading” required?
Microchipping
●
Caudal body—“tubing” will suffice.
Microchipping sites are similar to those used in nonvenomous species.
●
Use absorbable sutures to reduce postsurgical handling.
●
Treat the snake as an outpatient if possible.
Injection Sites
Anesthesia To avoid double handling, venomous snakes are often not premedicated. Anesthetic induction may be initiated by fitting a modified mask to the end of the tube holding the snake (Fig 11). Great care is required when removing the snake from the tube for intubation. An alternative method for anesthetic induction is to “head” the snake, intubate it while conscious, and immediately begin ventilating the patient. The author’s method of choice is to induce anesthesia by administering alfaxalone (5-8 mg/kg, intravenous, Alfaxan-CD RTU; Jurox, Rutherford, NSW, Australia) in the ventral coccygeal vein while the snake is restrained in a tube. After the injection, return the snake to the holding container and intubate once sedated. The selection of an anesthetic protocol will depend on the species of snake, site, and extent of injury or body region to be examined.
Figure 12. A locked and labeled hospital cage suitable for a venomous snake.
130
Johnson
minimize the chance of envenomation, it is often safer to decapitate the dead snake and place the head directly into a jar that contains decalcifying formalin solution.
Carcass Disposal Sever the head from the body and place it in a firm, sealable, and crushproof container (e.g., plastic jar or tub).
Disclaimer
Figure 13. Injection of intracardiac pentobarbitone in a coastal taipan, Oxyuranus scutellatus.
●
If it is still eating, medicate the snake via a food item.
If injectable medication is the only treatment option, choose a drug that requires a lower frequency of administration (e.g., ceftazidime every 72 hours, intramuscular, Fortaz; GlaxoSmithKline, Philadelphia, PA USA).
Hospitalization It is preferable to treat venomous snakes as outpatients. If hospitalization is required, ensure that a locked, labeled enclosure is available in a secure room (Fig 12). Access to the secure room that contains the venomous snake(s) should be restricted to authorized staff only. Snake hooks, jiggers, and tubes should be easily accessible outside and within the secure room.
Veterinarians treat venomous snakes at their own discretion and should be acutely aware of the risks involved. These notes are meant as a guide only. The advice contained within this article may change with time as new, safer equipment and techniques evolve. Veterinarians are advised to familiarize themselves with snake identification and make their own enquiries relating to specific species and procedural concerns.
References 1.
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Euthanasia As for many animals, a 2-stage euthanasia technique is recommended for venomous snakes. The euthanasia solution (Beuthanasia-D; Schering Plough Animal Health, New York, NY USA) is administered using the ventral coccygeal vein in a previously sedated or anesthetized snake. Cardiocentesis may be necessary if venous access is difficult or not possible (Fig 13).
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Necropsy 9.
Equipment. Protective eyewear and gloves should be worn when handling dead snakes because envenomation may still occur from a dead animal. Care should be taken when dissecting the venom gland, and this structure should be avoided if necessary. To
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Sutherland SK: Appendix— key to the identification of Australian snakes, in Sutherland SK (ed): Australian Animal Toxins. Melbourne, Australia, Oxford University Press, pp 33-39, 1983 Boyer TH: Common procedures with venomous reptiles. Vet Clin North Am Exotic Anim Pract 9:269285, 2006 Whitaker BR, Gold BS: Working with venomous species: emergency protocols, in Mader DR (ed): Reptile Medicine and Surgery (ed 2). St. Louis, MO, Saunders/Elsevier, pp 1051-1061, 2006 Shea GM: The distribution and identification of dangerously venomous Australian terrestrial snakes. Aust Vet J 12:791-798, 1999 Greer A: Elapidae—venomous land snakes, in Greer A (ed): The Biology and Evolution of Australian Snakes. Chipping Norton, Australia, Surrey Beatty and Sons, pp 132-246, 1997 Shine R: Anatomy of a snake, in Shine R (ed): Australian Snakes: A Natural History. Chatswood, Australia, Reed Publishing, pp 8-27, 1991 Peters JA: Dictionary of Herpetology. New York, NY, Hafner Publishing Co., 1964 Johnson RSP: What snake is that? Proceedings of the Combined Conference of the Association of Avian Veterinarians Australasian Committee and the Unusual and Exotic Pets Veterinarians, Australian Veterinary Association, Hobart, Tasmania, Australia, pp 225-230, 2010 McCracken H: Organ location in snakes for diagnostic and surgical evaluation, in Fowler ME, Miller RE (eds): Zoo and Wildlife Animal Medicine, Current Therapy 4. Philadelphia, PA, WB Saunders, pp 243-248, 1999 Isaza R, Andrews G, Coke R, et al: Assessment of multiple cardiocentesis in ball pythons (Python regius). Contemp Top Lab Anim Sci 43(6):35-38, 2004