Chemical Immobilization of Alpaca

Alpaca farmers, veterinarians and wildlife managers routinely need to immobilize alpacas to mark them for identification, provide veterinary treatment or to perform management functions. The term “immobilization” references any forced restriction of movement of all or part of an animal’s body, while chemical immobilization achieves this using drugs which have a range of intended effects. These effects may include unconsciousness with lack of sensation (anesthesia), or muscular paralysis while the animal is fully or partially conscious (sedation).

The immobilization of large wildlife species poses challenges with risks for both handlers and target animals, and this is where immobilization via chemical means is useful. An animal’s threshold of tolerance refers to the point at which a trapped animal will become aggressive upon human approach.¹

Alpaca Background

The alpaca (Vicugña pacos) is a domesticated member of the camelid family (Camelidae). This group of animals also includes llamas, guanacos, vicunas and camels. All except for camels are New World camelids, which are also called lamoids.² Native to the high altitudes of the Andes of Chile, Peru and Bolivia, alpacas have been valued for their luxurious fleece for thousands of years.

Alpacas are the smallest of the domesticated camelid species. Theyare slender-bodied animals with a long neck and long legs, a short tail, a small head, and large, tapering ears. The weight of an adult alpaca ranges from 120 to 140 lbs, with a height ranging from 2 to 3 feet.

There are two breeds of alpaca: These are known as huacaya and suri, although they are technically one species.³ Over 90% of alpacas are huacayas. The fleece of the huacaya grows perpendicular to the skin, which gives this animal a wooly appearance. Suris have a straight fleece that curls downward, resembling dreadlocks. Alpaca coats vary in color from black or brown to pale yellow and white. Their wool fibers are hollow, which makes them able to insulate very well and to absorb moisture.⁴ As a result, alpaca farming has become a worldwide industry. Alpacas are shorn once a year, usually in the Spring when the weather is warm.

Alpacas are pseudo-ruminants, which means that they possess a single stomach divided into three compartments instead of four, like other ruminants. They are grazers, feeding on grasses from the mountainsides and valleys of the Andes. Alpacas on farms are typically fed a combination of fresh grass and hay.

For short medical procedures on alpaca, withholding food and water may be unnecessary, but for longer procedures or ones that necessitate recumbency, food should be withheld for 24 to 36 hours beforehand, and water should be withheld for 12 hours prior. Bloating can occur in camelids; aspiration of first stomach compartment (C1) contents is known to be a greater risk.⁵

Sedation and Anesthesia of Alpaca

Although they are the smallest of the New World camelids, most adult alpaca are large enough to be considered difficult to handle in the event that they become frightened or agitated. This being the case, chemical agents (sedatives and/or anesthetics) may be delivered by hand to a restrained alpaca by using a pole syringe, or by using a capture gun (either a handgun or along gun). Capture guns are fired by CO₂ gas cartridges or with .22 caliber blanks. Syringes (often called darts) are loaded through a breech, one shot at a time. The effective range may be up to 60 yards.⁸ Remote chemical immobilization is often carried out by approaching an alpaca and shooting a dart from a snowmobile, an off-road vehicle, or from the ground.

The chemical immobilization of alpaca carries inherent risks. These include, but are not limited to capture myopathy, hypothermia, hyperthermia, respiratory depression/arrest, aspiration and cardiac arrest. Additionally, if the onset of immobilizing drugs is slow, the risk of physical injury such as lacerations, limb injuries, head trauma etc. is increased. It is therefore extremely important for personnel to be familiar with animal handling and immobilization techniques, as well as potential emergencies.

Depending on the procedure(s) being performed, an alpaca may be immobilized using heavy sedation or general anesthesia. Drug choices and combinations must be of proven safety and calculated for the alpaca’s weight, age, physiological and reproductive status and body condition.^9,10

Given their level of domestication, most camelids (llamas, alpacas and camels) are typically agreeable when it comes to handling, thus physical restraint and local anesthetic techniques are often used to provide immobility and analgesia. General anesthesia techniques are similar to those for ruminants and horses. Regurgitation of compartment one (C1) of the stomach contents (which can occur in many chemically-immobilized ruminants), postoperative nasal congestion and associated respiratory distress postextubation are potential hazards associated with anesthesia in alpaca.⁷

Immobilizing Agents for Alpaca

In the U.S., the possession and use of drugs used to immobilize alpaca is governed by federal and state regulations. All drugs currently used to sedate or immobilize wild animals are prescription drugs and must be used by or on the order of a licensed veterinarian. This requires that a veterinarian must be involved in the process, but it does not mean that a veterinarian is physically present during the immobilization process. Some drugs used chemical immobilization are also classified as controlled drugs, the possession of which requires a U.S. Drug Enforcement Agency registration number, special record keeping and special storage. Non-veterinarians using prescription drugs should receive sufficient training in their use.

The classes of immobilizing drugs used on alpaca include:

Tranquilizers/Sedatives: Tranquilizers are used in wildlife immobilization primarily as adjuncts to primary anesthetics (e.g., ketamine, carfentanil) to hasten and smooth induction and recovery and to reduce the amount of the primary agent required to achieve immobilization. Valium is used primarily for small mammals as an anticonvulsant adjunct to ketamine anesthesia, and it is also an excellent muscle relaxant.

The α-adrenergic tranquilizers (e.g., xylazine or Rompun, medetomidine) are potent sedatives that can be completely antagonized.⁹ These are often combined with ketamine, Telazol, or carfentanil. By themselves, they are capable of heavily sedating animals, particularly ungulates, to the point of relatively safe handling. However, animals sedated with these tranquilizers generally can be aroused with stimulation and are capable of directed attack.

Paralytic Drugs: The neuromuscular blocking (NMB) or paralytic drugs are some of the earliest drugs used for the chemical immobilization of wildlife, and are being used less frequently today than in years past. Despite their long history, NMB drugs are generally inferior to modern drugs. There are two major deficiencies of NMB drugs. One is that NMB drugs have a very low safety margin: dosage errors of only 10% can result in either no effect (underdosing) or death by asphyxia (overdosing). Mortality rates as high as 70% have occurred.¹⁰

The second deficiency is that NMB drugs are virtually devoid of central nervous system effects because of their inability to cross the blood-brain barrier. Thus, an animal paralyzed with NMB drugs is conscious, aware of its surroundings, fully sensory, and, as such, can feel pain and experience psychogenic stress yet is physically unable to react.^9,10 Because of these deficiencies, NMB drugs should be used judiciously.

Dissociative Anesthetics: This group of drugs (e.g., ketamine, tiletamine) is characterized by producing a cataleptic state in which the eyes remain open with intact corneal and light reflexes. Ketamine is one of the most widely used drugs for wildlife immobilization because of its efficacy and safety. Tiletamine is unavailable as a single product and it is combined in equal proportions with the diazepinone tranquilizer, zolazepam (e.g., Telazol).When used singly, ketamine usually cause rough inductions and recoveries, and convulsions are not uncommon.¹¹ Because of this, they are usually administered concurrently with tranquilizers or sedatives. There is no complete antagonist for ketamine or Telazol.

Opioid Anesthetics: The opioids have been used for the chemical immobilization of wildlife since the 1960s and are the most potent drugs available for this purpose. The most commonly used opioid for wildlife immobilization is carfentanil. A major advantage in the use of opioids is the availability of specific antagonists. The potency of opioids, such as etorphine and carfentanil, is both an advantage and disadvantage. The advantage is the reduced volume of drug required for immobilization makes them the only class of drugs capable of remote immobilization of large animals. The disadvantage is that they are potentially toxic to humans. Death is almost always due to respiratory failure. Opioids should never be used while working alone or without having an antagonist on hand.⁹

Recovery and Reversal Agents

As with most other mammals, the duration of anesthesia in alpaca will be influenced by the drugs used, age, sex, body weight, procedure performed and the amount of stimulus during the procedure. Whether sedation or general anesthesia has been used, reversal agents are often required to neutralize sedation or anesthetic agents. These allow the alpaca to completely recover from being anesthetized prior to release.

Concerns in the area of humane treatment and conservation have helped to bring about the refinement of chemical immobilization protocols and drug development to keep these within safety margins through the use of novel anesthetics and combinations of true anesthetics, neuromuscular blockers and tranquilizers.¹¹ The use of antagonists (reversal agents) to anesthetics is now widely employed, as this avoids the undesirable and potentially harmful effects of drugs and facilitates speedy recovery from chemical immobilization events.^9,10

Veterinary custom compounding pharmacies have widely expanded the variety, availability and efficacy of immobilizing drugs through the development of custom formulations for wildlife such as alpaca. Some of these are available in kit form, which include both the immobilizing drugs and antagonists.