Chemical Immobilization and Sedation in Alpaca

Over the years, the development of non- and minimally invasive medical procedures has allowed researchers, veterinarians and wildlife management personnel to obtain certain types of biological data without the need to physically handle animals. However, some information can still only be obtained by capturing individual animals.¹ Captures are also important for marking individuals in the case of some studies.

Technological advances such as global positioning system (GPS) collars, heat sensitive transmitters and advanced physiological monitoring equipment now allow detailed research on many species, but require the initial capture and manipulation of individual animals.²

Alpaca: Background and Biology

The alpaca (Vicugña pacos or Lama pacos) is the smallest relative of the camel. Alpacas are lamoids, a word used to reference several species of South American camelids (Camelidae). Lamoids are also known as New World camelids. This particular group of animals includes llamas, alpacas, vicuñas, and guanacos. Like camels, these animals are believed to have originated in North America over 40 million years ago, with lamoids migrating to South America and camels migrating west via the Bering Strait, later becoming extinct in North America.³

Lamoids vary by size and purpose; some have been bred for use as pack animals and others for their fleece.³ Today, alpacas are the most widely-used lamoids for fleece production. The alpaca encompasses two breed types: the huacaya and the suri. Huacayas account for about 90% of all alpacas.^4,5 The two breed types differ primarily in terms of the properties of their fleece. The fleece of both breeds is lightweight, strong, high in insulation value and very resistant to moisture. Alpaca wool fibers are hollow, which gives them the ability to insulate very well, and to absorb moisture. As a result, alpaca farming has become a worldwide industry.

Drugs Used for Chemical Immobilization of Alpaca

The effects of immobilization on alpaca can differ considerably according to the capture methodology employed. In this regard, the literature agrees that captures by remote delivery of immobilizing drugs via darting lower an alpaca’s stress levels, thus decreasing the capture effects and risks compared to other techniques.⁶ This is a chief reason why chemical immobilization is becoming a preferred capture method, particularly in the case of larger mammals.

The three classes of immobilization drugs that are used on alpaca include opioids, cyclohexamines and neuroleptics.

Opioids

• The most potent drugs available for immobilization
• A major advantage is the availability of specific antagonists
• Reduced volume of drugs are typically required
• The only class of drugs practical for remote immobilization of large animals
• Potentially toxic to humans

Cyclohexamines

• Also known as dissociative agents
• Produce altered consciousness
• Dissociate mental state from environmental stimulation
• Retain many vital reflexes
• The animal cannot walk but can move tongue, blink, swallow
• The animal may feel some pain
• Common cyclohexamines include Ketamine, tiletamine
• Cyclohexamines should not be used alone and are not reversible
• Should be used in conjunction with other drugs, such as neuroleptics

Neuroleptics

• Also referred to as tranquilizers
• Produce calmness and relaxation
• Do not cause loss of consciousness or alleviate pain perception
• Can cause death before they cause loss of consciousness
• Used in conjunction with other drugs (e.g., cyclohexamines)
• Common neuroleptics include zolazepam, diazepam, xylazine
• Common reversal agents include yohimbine, tolazoline

Chemical Immobilization Techniques

Less stress on alpaca is likely to occur in a zoo or on a farm than in the field, since animals in these settings tend to be far more acclimatized to human handling. Additionally, since alpaca have been so heavily domesticated, most are less prone to capture stress than other hoofstock species.

Intramuscular hand injection can be used when working with alpacas that are cooperative. When hand injecting, rapid delivery while minimizing risk to the handler or animal is essential. Pole syringes are also widely used for this purpose, since these afford greater distance than approaching an animal for a hand injection without resorting to remote delivery systems. As with hand injection, larger bore needles should be used to ensure complete drug delivery.

Remote chemical immobilization can be carried out by approaching alpacas and shooting a dart from a vehicle or from the ground. While this can significantly reduce stress compared to physical capture methods, it still impacts the alpaca’s stress levels. A frightened alpaca will have an increased heart rate, higher levels of cortisol and other stress-related biochemicals.⁶ An approach from the ground on foot will produce lower stress levels in alpaca, because they will be less frightened than if a noisy vehicle is used.

If the alpaca’s skin has been breached by anything larger than a hypodermic needle (including biopsy instruments) during procedures, analgesia will be required. Invasive surgeries should be conducted using general anesthetics with the animal at a surgical plane; intraoperative analgesia that continues after anesthetic recovery should be provided in some form.¹ For analgesic drugs, doses and frequencies of administration are more difficult to gauge, even with close clinical observation for discomfort.⁷ These observations can be even more difficult to make in the field than in a clinic or zoo setting, compounding the difficulty in such assessments. Intubation is recommended for alpaca that need to be anesthetized for longer than 20 minutes.⁶

Most of the opioid analgesics (Buprenorphine, Fentanyl, Butorphenol, Oxymorphone, etc.) will not be effective after 12 hours after administration. Longer‐lasting, non‐steroidal anti‐inflammatory analgesics (NSAIDs) such as Meloxicam, Carprofen, Flunixin, Ketoprofen,etc. have longer durations of action than opioids, and can be administered in conjunction with opioids to increase potency of effect and duration of action.⁷

Reversal Agents for Alpaca

Reversal agents are often required to neutralize sedation or anesthetic agents, thus allowing the alpaca to completely recover from being anesthetized. This is even more important in the field than in a clinic, farm or zoo setting, because a chemically-compromised alpaca will be in danger of injury and other hazards.

In the alpaca, duration of anesthesia will be influenced by the drugs used, age, sex, body weight, procedure(s) performed and the amount of stimulus during the procedure. Due to the variety of factors that influence duration of anesthesia, the literature maintains that anesthetic drugs should be titrated to effect. If anesthesia is being maintained by a gas anesthetic (e.g., isoflurane), titration of anesthetic depth can be controlled almost immediately by adjusting the amount of anesthetic gas being administered to the animal.⁷

On the other hand, injectable anesthetics and sedatives do not have this flexibility. Once a dose has been administered, it cannot be “dialed-back” to facilitate the end of anesthesia to coincide with the end of the procedure.⁸ In such cases, reversal drugs can be used to bring about the desired effect.

Atipamezole is a synthetic α2-adrenergic antagonist. Developed to reverse the actions of compounds such as medetomidine and dexmedetomidine, atipamezole safely and reliably reverses the effects of these compounds and is widely used in small and large animal practices, as well as in wildlife applications.⁹

Naltrexone hydrochloride is an opioid receptor antagonist that is used in veterinary medicine to block receptors as a reversal agent for opiate agonists such as butorphanol. 

In recent years, great care has been taken with chemical immobilization protocols and drug development to keep these within safety margins through the use of novel anesthetics, including combinations of true anesthetics, neuromuscular blockers and tranquilizers.² As a result, modern chemical immobilization techniques have dramatically reduced the side-effects of drugs and mortalities. Additionally, the use of antagonists to anesthetics is now widely employed, as this avoids the undesirable and potentially harmful effects of drugs and facilitates the speedy of animals’ recovery from chemical immobilization.^1,2

The drug formulations available for immobilizing alpaca and large wildlife species have been refined to a degree that eliminates much of the risk that existed years ago. With the right drug formulations, proper planning and safety precautions in place, experienced personnel can have the expectation of effective and incident-free chemical immobilization of alpaca.