Chemical Immobilization of Dromedary Camels

The chemical immobilization of dromedary camels is needed on occasion in order to mark them for identification, provide veterinary treatment or to perform management functions. “Immobilization” refers to any forced restriction of movement of all or part of an animal’s body, while “chemical immobilization” achieves this using drugs with a range of intended effects. These may include unconsciousness with lack of sensation (anesthesia), or widespread muscular paralysis while the animal is fully or partially conscious (sedation).

The immobilization of large or potentially dangerous animals poses challenges with risks for both handlers and target animals, and this is where immobilization via chemical means is useful.¹ Camels were first domesticated 3,000 years ago, and today, approximately 90% of the world’s camels are in fact domesticated.² This reduces much of the capture stress that camels might suffer as compared to other wild animals, yet chemical immobilization does still carry some risks for complications in these animals.

The Dromedary Camel

The one-humped dromedary camel (Camelus dromedarius) remains an important resource in its range across northern Africa, the Middle East and western Asia. The ancestors of modern camels originated in North America, later becoming extinct there. It is believed that one-humped camels diverged from their two-humped ancestors (which later became the two-humped species, the Bactrian camel, C. bactrianus and C. ferus) around 4.4 million years ago.^1,2

Camels were used as pack animals on the Silk Road, the network of routes used by traders between Europe and Asia for more than 1,500 years² because they could carry more weight than horses or donkeys, needed less water and were able to thrive on tough desert plants. Today, camels are still used for their wool, milk, meat and leather,³ and are engaged extensively in the tourism industry.

The dromedary camel (also known as the Arabian camel) has not occurred in the wild for nearly 2,000 years due to its widespread domestication. Dromedary camels are herbivorous, with a diet consisting of foliage, dry grasses and thorny plants that are common in the desert. Their thick, bifurcated upper lips allow them to access and eat things that other desert animals cannot. When foraging, groups of dromedary camels tend to spread out over large areas eat sparingly from numerous plant sources.

While the dromedary camel’s hump consists of fat and fibrous tissue (rather than water) that are used for energy storage, these animals are uniquely adapted to maintain their internal homeostasis and hydration whether water is plentiful or scarce. When water is available, they can drink up to 30 gallons of water in less than 15 minutes.^1-3

Dromedary camels are diurnal and generally timid, although they are quite social among themselves in groups or herds. In most cases, they can be found in groups of four to six. In family groups, the male is dominant and brings up the family from the rear, with the several females with which he mates taking turns leading the group. Adult dromedary camels stand approximately 7 feet high at the hump(s). They can run up to 40 miles per hour at a sprint, and sustain speeds of up to 25 miles per hour.³

In the 1840's, dromedary camels were introduced into Australia to assist in the exploration of the inland continent, which is similar to the dromedary camel’s native habitat. Today, there are over one million feral camels in the rangeland ecosystems of Australia. Unfortunately, these animals are negatively impacting the natural environment to a significant degree. As a result, radio-collared camels are being used in Australia to enhance population control programs.⁴

Dromedary Camels and Chemical Immobilization

Dromedary camels 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 camel by using a pole syringe, or by using a capture gun (either a handgun or along gun). Capture guns are fired by CO₂gas cartridges or with .22 caliber blanks. Darts containing immobilizing drugs 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 a camel and shooting a dart from a helicopter, an off-road vehicle, or from the ground.

The chemical immobilization of dromedary camels 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 (induction) of anesthesia is slow, the risk of physical injury such as lacerations, limb injuries, head trauma etc. is increased. It is therefore extremely important for personnel in the field and/or support staff to be familiar with animal handling and immobilization techniques, as well as potential emergencies.

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

Given their level of domestication, dromedary 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 dromedary camels.⁷

Immobilizing Agents for Dromedary Camels

All drugs that are currently used to sedate or immobilize wild animal species 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 mandate 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 must receive adequate training in their use.

The classes of immobilizing agents used on dromedary camels include:

Paralytic Drugs: 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 drug formulations. 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 more or less 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 with great care.

Tranquilizers/Sedatives: These drugs are used primarily in wildlife immobilization 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.

Dissociative Anesthetics: This group of drugs (ketamine, tiletamine) is characterized by producing a cataleptic state in which the eyes remain open with intact corneal and light reflexes. Ketamine is probably 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 causes 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: Opioids have been used for the chemical immobilization of wildlife since the 1960s and are still the most potent drugs available for this purpose. The most commonly used opioid in 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. A disadvantage is that they are potentially toxic to humans. Thus, opioids should never be used while working alone or without having an antagonist on hand.⁹

Drug Reversal Agents

The duration of anesthesia in dromedary camels 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, thus allowing the camel to completely recover from being anesthetized.

Concerns in the area of humane treatment 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, including combinations of true anesthetics, neuromuscular blockers and tranquilizers.¹¹ The use of antagonists 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

The variety, availability and efficacy of immobilizing drugs have been widely expanded by veterinary custom compounding pharmacies through the development of custom formulations for wildlife such as dromedary camels. Some of these are available in kit form, which include both the immobilizing drugs and their specific reversal agents.