Wildlife Veterinary Medicine
Wildlife veterinarians are licensed animal health professionals who specialize in treating many different types of wildlife, including birds, amphibians, reptiles, and mammals. They may work either in a veterinary office setting or in the field, but their primary clinical duties are often in the field. Wildlife veterinarians often work in conjunction with wildlife rehabilitators at rehabilitation facilities. They also must be able to interact and communicate effectively with veterinary technicians, wildlife officials, and members of the public.1
When wildlife is threatened by poaching, habitat loss and pollution, unexpected outbreaks of disease can be catastrophic. Consequently, wildlife veterinary expertise is vital for controlling disease, giving the right medical treatment to reduce the suffering of sick or injured individuals and successfully rehabilitating endangered animals.
The typical duties of a wildlife vet may include performing exams, giving vaccinations, taking blood samples, administering fluids, performing surgeries when needed, prescribing medications, evaluating and treating wounds, taking x-rays and ultrasounds, cleaning teeth, assisting with captive breeding programs and providing intensive care for very young animals abandoned by their parents.1
Field Wildlife Sedation
Many of the wildlife veterinarian's above duties include the sedation of animals for procedures. This is particularly true where there is a need for the collaring, tagging or relocation of large and/or potentially dangerous wildlife. Field wildlife anesthesia is often necessary for both invasive (e.g., surgical) and noninvasive (e.g., blood collection, collaring, metabolic) procedures. Anesthesia for noninvasive procedures is commonly utilized for the safety of the investigators and the animals. Even minimally invasive procedures (such as blood collection, ear tagging, or radio-collar placement) can be stressful for the animal and result in self-trauma or iatrogenic injury during restraint and struggling.2
General anesthesia is inherently a veterinary medical endeavor and thus should be conducted under the supervision and guidance of a licensed veterinarian. In almost every case, the drugs needed for an immobilization are controlled substances or prescription drugs which must be acquired by a licensed veterinarian. All anesthetic protocols should be designed by a licensed veterinarian and ideally with the guidance of a board-certified anesthesiologist or wildlife veterinarian.
Unlike domestic animal anesthesia, many field immobilizations are conducted by biologists and field technicians. Nonveterinary personnel should only perform and monitor anesthesia when properly trained by veterinarians or other specialists, and such training should be regularly reviewed and maintained.3
Developing the anesthetic plan
Size, habitat, and activity level can determine drug choice and delivery method for the target species. Protocols appropriate for a small carnivore may not translate to larger, more-dangerous animals, as the consequences of sudden arousal are very different. While a given wildlife veterinarian may have a wide range of experience across the species he or she is likely to encounter, consultation with veterinarians who have anesthetized the target species in field or captive settings is a valuable tool for designing an appropriate protocol.3
Factors to consider when developing an anesthetic plan include the expected degree of tissue trauma, the potential for hemorrhage, the potential for cardiopulmonary instability, the expected overall condition of animals given the season and climate, the level of pain, and the depth of anesthesia required. Operative risk refers to the uncertainty and the potential for an adverse outcome (including prolonged behavioral changes, morbidity, and mortality) as a result of anesthesia or surgery. Risk depends on the skills of the anesthetist and surgeon, the anesthetics used, the resources available, the environmental working conditions, and the physical status of the patient, the duration of anesthesia, and the level of preoperative stabilization.
Capture Conditions in the Field
The veterinarian must be able to safely deliver the chosen drug combination in the field situation. In many situations, remote delivery of drugs to an unrestrained animal is faster and less stressful to the animal than is physical restraint in a trap.2 Animals can be approached by ground vehicle, stalking on foot, or helicopter however, extended chasing or long restraint in a trap can increase the risk of the animal's self-injury.1
Remote drug delivery equipment such as dart projectors carry intrinsic risk of injury to the animal Such devices should only be used by trained personnel familiar with the terrain and species at hand. Terrain and capture conditions play an important role if an anesthetic protocol involves a slow induction or recovery. A slow induction protocol increases the chance of overexertion and myopathy as well as increasing the likelihood of escape or injury from environmental hazards.2
Anesthetic Protocols and Drug Types
The veterinarian and involved investigators should consult the available primary and secondary literature related to the target species. In general, the two broad categories of anesthetic agents are inhaled or injectable agents. Injectable anesthetics are further differentiated as reversible and nonreversible. Injectable agents are typically administered by an intravenous (IV) or intramuscular (IM) route. Some drugs are appropriate for either route while others can only be administered intravenously. Any anesthetic protocol must take into account the potential for secondary toxicosis in a predator, scavenger, or human that may consume a recently anesthetized subject.3
Inhalant anesthetics are widely used in a clinical setting and possess unique advantages and disadvantages for use in a field setting. Isoflurane and sevoflurane are the two most-commonly used inhalant agents in field veterinary medicine. Unlike injectable anesthetics, inhalants are administered and expelled via the respiratory system. This allows for a rapid and precise adjustment of the anesthetic depth of the patient.
There are several types of intravenous anesthetics that are commonly used by veterinarians in traditional practices and in the field. Some of these, like propofol, are ultrashort-acting injectable anesthetics that are labeled for IV administration. Alfaxalone is a neurosteriod, with no analgesic properties, that has recently become FDA-approved in the United States. Like propofol, alfaxalone anesthesia can be prolonged through repeat IV dosing of the drug.
Intramuscular anesthetics are also widely used in wildlife veterinary medicine. Many of these are used for immobilization prior to procedures being performed with the animal under anesthesia with IV or inhalant agents.
Ketamine is a fast-acting dissociative anesthetic that is used in combination with a tranquilizer-sedative, usually a benzodiazepine or oralpha-2 agonist. Immobilizations with combinations including ketamine provide a rapid onset of action, immobilization within 10 min, and long duration (up to 2 h).
Tiletamine-zolazepam (TZ) is a widely used commercial combination of a dissociative anesthetic and a benzodiazepine sedative. When dosed appropriately, this combination provides a smooth induction, good muscle relaxation, and analgesia. Tiletamine-zolazepam can be administered both IV and IM. While the tiletamine is not reversible, the zolazepam can be antagonized with flumazenil.
Alpha-2 adrenergic agonists, such as xylazine, detomidine, medetomidine, dexmedetomidine, and romifidine, are potent central nervous system depressants but do not produce general anesthesia unless combined with another drug. This class of drugs possesses sedative, muscle relaxant, and analgesic properties. When combined with opioids or dissociative anesthetics, these drugs help to provide reliable anesthesia.
Opioids have been used extensively in the immobilization of wildlife. They are relatively fast-acting, and provide analgesia and sedation, but lack the muscle relaxation seen with alpha-2 agonists. Common side effects seen with opioid combinations include excitation, regurgitation, severe respiratory depression and hypoxemia, muscle rigidity, and renarcotization.2
All anesthetic plans must take into account human and animal safety. Human injuries and deaths during field immobilizations have occurred from animal attacks, helicopter accidents, drug exposure, and environmental hazards. It is critical that all members of the field team understand the risks inherent with field anesthesia and that appropriate human emergency procedures have been discussed.3
2Caulkett N, Arnemo J. 2007. Chemical immobilization of free-ranging terrestrial mammals. In: Lumb and Jones’ veterinary anesthesia,4th Ed., Thurmon J, Tranquilli W, Grimm K, editors. Blackwell, Ames, Iowa, pp. 807–831.
3Sathya K. Chinnadurai, S., Strahl-Heldreth, D., Fiorello, C., Harms, C. (2016) Best-Practice Guidelines for Field-Based Surgery and Anesthesia Of Free-Ranging Wildlife. I. Anesthesia and Analgesia. Journal of Wildlife Diseases: April 2016, Vol. 52, No. 2s, pp. S14-S27
About NexGen Pharmaceuticals
NexGen Pharmaceuticals is an industry-leading veterinary compounding pharmacy, offering sterile and non-sterile compounding services nationwide. Unlike other veterinary compounding pharmacies, NexGen focuses on drugs that are difficult to find or are no longer available due to manufacturer discontinuance or have yet to be offered commercially for veterinary applications, but which still serve a critical need for our customers. We also specialize in wildlife pharmaceuticals, including sedatives and their antagonists, offering many unique options to serve a wide array of zoo animal and wildlife immobilization and anesthesia requirements.
Our pharmacists are also encouraged to develop strong working relationships with our veterinarians in order to better care for veterinary patients. Such relationships foster an ever-increasing knowledge base upon which pharmacists and veterinarians can draw, making both significantly more effective in their professional roles.
Disclaimer
The information contained in this blog post is general in nature and is intended for use as an informational aid. It does not cover all possible uses, actions, precautions, side effects, or interactions of the medications shown, nor is the information intended as medical advice or diagnosis for individual health problems or for making an evaluation as to the risks and benefits of using a particular medication. You should consult your veterinarian about diagnosis and treatment of any health problems. Information and statements have not been evaluated by the Food and Drug Administration ("FDA"), nor has the FDA approved the medications to diagnose, cure or prevent disease. Medications compounded by NexGen Pharmaceuticals are prepared at the direction of a veterinarian. NexGen Pharmaceuticals compounded veterinary preparations are not intended for use in food and food-producing animals.
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