Capture Myopathy in Dromedary Camels During Capture and Chemical Immobilization

The dromedary camel has not occurred in the wild for nearly 2,000 years, having been widely domesticated beginning approximately 3,500 years ago. Domesticated dromedary camels are now found in regions of the Middle East, northern India, and northern Africa (most commonly in the Sahara Desert).¹ There is also a large population of feral dromedary camels in Australia (see below).

According to fossil evidence, the ancestors of modern camels evolved in North America during the Palaeogene period and later spread to Asia, later becoming extinct in North America.² Camels were used almost exclusively as pack animals on the Silk Road, the network of routes used by traders between Europe and Asia for more than 1,500 years. This was because they could carry more weight than horses or donkeys, needed less water and were able to thrive on tough desert plants.

Dromedary camels are herbivorous, with a diet consisting of foliage, dry grasses and thorny plants that are common in the desert. Their thick, split lips allow them to access and eat things that other desert animals cannot. When foraging, dromedary camels tend to spread out over large areas eat sparingly from numerous plant sources.

While the 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 tend to “fill up,” drinking 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 when 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.

Dromedary camels are polygamous, with a breeding season that spans from November through March. Gestation lasts up to 13 months, with one calf or occasionally twins being born. Calves can usually stand within 8 hours, and remain with the herd until they are old enough to become independent.²

Capture Myopathy: Causes and Clinical Signs

Capture myopathy (CM) is a serious condition that has the potential to occur in both wild and domestic animals in which muscle damage results from extreme exertion or stress. CM is also known as exertional myopathy, overstraining disease and exertional rhabdomyolysis.⁴ It most often occurs as a result of capture, transport or chemical immobilization, but it can also be the result of other natural causes of stress, such as in prey animals attempting to avoid or struggling with predators.⁵ Capture myopathy is of ethical concern in cases when it is a cause of death in animals being handled by humans (such as in chemical immobilization events).

Capture myopathy can occur in nearly any animal under extreme stress, although it is believed that some species may be more predisposed to it than others.⁶ It has been most widely studied in ungulates and birds, although it is believed to potentially affect any captured wildlife species.⁵

Capture myopathy can occur naturally when an animal is attempting to avoid predation, but since dromedary camels have few predators and are almost completely domesticated, for the purposes of this discussion, it will be the result of these animals being captured and/or immobilized. When animals overexert themselves (e.g., attempting to elude a capture team) to the extent that physiological imbalances develop and give rise to severe muscle damage, capture myopathy results.⁵ Increased ambient temperatures and repeated chemical immobilization can increase the risk of a camel suffering from capture myopathy.⁷

Dromedary camels were first introduced into Australia in the 1840's to assist in the exploration of inland Australia. Today, there are over one million feral camels in the rangeland ecosystems of Australia.⁸ Unfortunately, these animals are causing significant damage to the natural environment as well as having a negative social, cultural and economic impact across their range in central Australia.

Today, radio-collared dromedary camels are being used to enhance population control programs. This involves immobilizing individual camels, attaching a telemetry collar, and releasing the collared animal to re-join its herd. The collared individuals are then tracked via GPS and communications satellites.⁸ This routinely-performed procedure carries the risk of inducing capture myopathy in these animals.

Clinical signs of capture myopathy in dromedary camels can vary depending on the cause of exertion.⁵ The method of capture and restraint is also a primary factor in occurrences of CM. Capture myopathy may result in sudden death, but surprisingly, clinical signs may develop hours, days, or up to two months following capture.⁴ Clinical signs during early onset include elevated respiratory rate, heart rate, and body temperature.^4,6 Body temperature increases during exertion, with higher temperatures being associated with death due to CM.⁴

Muscle spasms, stiffness and lameness are also clear signs of CM. Animals often become recumbent and may stumble. If dark red-colored urine is noted, this is an indication that the animal's muscles are breaking down and that its kidneys have been severely affected.^5-7 Death of the animal usually follows. If the animal survives the acute stage of the condition, scarring of heart and skeletal muscle tissue may permanently debilitate the animal.⁷ Upon necropsy, light-colored skeletal and cardiac muscle is indicative of capture myopathy being the cause of death.

Preventing Capture Myopathy in Dromedary Camels

Given that there is no treatment for capture myopathy, prevention is the best method of avoiding this condition. Extreme care should be taken in handling species that tend to be more susceptible to capture myopathy. Anesthetic protocols consisting of good anesthetic agents can aid significantly in preventing capture myopathy in camels. In such cases, the remote delivery of anesthetic agents is a far superior methodology to trapping an animal prior to the anesthetic event.

The capture team should be thoroughly aware of the risks of capture myopathy and make every effort to prevent its onset. Camels should only be captured when necessary, and the negative effects that capture may have on an animal's health should always be considered before beginning a capture or initiating an anesthetic event.^8-10 Capture methods that minimize animal stress, struggling and handling time should be utilized. It has been reported that using a combination of Xylazine HCL and Ketamine HCL for sedation/anesthesia may decrease the chance of capture myopathy, but this is by no means a guarantee of avoiding this condition in dromedary camels.⁶