Capture Myopathy in Alpaca During Capture and Chemical Immobilization

The alpaca (Lama pacos or Vicugna pacos) is a domesticated member of the camel family (Camelidae, orderArtiodactyla). Believed to be derived from the vicuña (Vicugna vicugna) several thousand years ago, it is closely related to the other lamoids (South American camelids) such as the llama (Lama glama) and the guanaco (L. guanicoe).¹ Alpacas are native to the mountainous areas spanning from southern Colombia and Ecuador to northern Chile and northern Argentina.² As such, they are the most limited in range and the most specialized of the lamoids.

Alpacas are slender-bodied animals with a long neck and long legs, a short tail, a small head, and large, pointed ears. They are the smallest of the lamoids, standing approximately 35 inches high at the shoulder and weighing 120 to 145 pounds.¹ The alpaca’s shaggy coat varies in color from black or brown through gray and tan to pale yellow and white.

Alpacas are the most widely-used lamoids for fleece production. The fleece of the alpaca is lightweight, strong, high in insulation value and resistant to moisture. It has been reported that during the height of the Incan civilization, the wearing of robes made of alpaca fleece was reserved for the nobility and royalty.³ In pre-Columbian times, two breeds of alpaca, the huacaya and the suri, were developed. The fleece of the huacaya is somewhat shorter and coarser, while the fleece of the suri is long, fine and silky. Although the suri and huacaya are not separate species, approximately 90% of alpacas are huacaya. These animals are usually sheared every two years for their fleece.

Alpacas are social herd animals that live in family groups comprised of an alpha male, females, and their young. They are gentle, inquisitive and intelligent. As prey animals, they are cautious and warn the herd when intruders are present by making sharp, high-pitched inhalations. The herd may attack smaller predators with their front feet, and are known to spit and kick.^1,3 Alpacas have a natural life span of 15–20 years.

Capture Myopathy Risk in Alpacas

Capture myopathy (CM) is a dangerous condition that can occur in both wild and domestic animals wherein muscle damage results from extreme exertion, struggle, or stress. This condition is also known as exertional myopathy, overstraining disease and exertional rhabdomyolysis.⁴ Capture myopathy 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 predator animals.⁵ Capture myopathy is of particular ethical concern in cases when it is a cause of death in animals that are in the care of humans, such as in chemical immobilization events.

Capture myopathy can occur in any animal under extreme stress, although it is believed that some species may be more predisposed to it than others due to their temperament and physiological characteristics.⁶ Capture myopathy has been most widely studied in ungulates and birds, although it is believed that it can potentially affect any captured species. It has also been observed in coyotes, badgers, primates, and many other species.⁵

Clinical Signs and Causes of Capture Myopathy

Capture myopathy can occur naturally when an animal is attempting to avoid predation, but since alpacas have few predators and are largely domesticated, for the purposes of this discussion, it will be the result of these animals being captured and/or chemically immobilized. Like other animals, alpacas are not adapted to struggle for long periods of time in human-constructed restraints.⁶ When animals overexert themselves (e.g., attempting to flee a capture team or struggling in a trap) to the extent that physiological imbalances develop and result in severe muscle damage, capture myopathy results.⁵ Increased environmental temperatures and repeated chemical immobilization can increase the risk of animals suffering from capture myopathy.⁷

Clinical signs of capture myopathy in alpacas can vary depending on the cause of exertion.⁵ Thus, the method of capture and restraint is also a determinant in occurrences of CM. The available literature states that capture myopathy may result in sudden death, or that clinical signs may develop hours, days, or up to two months following capture.⁴ The 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. The increase in body temperature can be above 42°C.⁴

During a chemical immobilization event, muscle spasms, stiffness and lameness are also clear signs of capture myopathy. 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 an 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 (see photo).

Preventing Capture Myopathy in Alpacas

There is no treatment for capture myopathy, thus prevention is the best method of avoiding this condition. Care should be taken in case of handling of animals that tend to be more susceptible to capture myopathy. An anesthetic protocol consisting of good anesthetic agents can aid significantly in preventing capture myopathy in alpacas. In such cases, the remote delivery of anesthetic agents is a superior methodology to trapping an animal prior to sedation or anesthesia being used.

The team handling alpacas should be thoroughly aware of the risks of capture myopathy and make every effort to prevent its occurrence. Alpacas 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 can decrease the chance of capture myopathy, but this is by no means a guarantee of avoiding this condition in alpacas.⁶