Capture Myopathy in Impala Antelope
The iconic impala (Aepyceros melampus) occupies the savannas of eastern and southern Africa and the bushveld regions of South Africa and is the most common antelope in these areas. As with other antelopes, it is a member of the family Bovidae, and the only member of the subfamily (or tribe) Aepycerotini.1 It is medium-sized, with slender, well-developed legs and a long neck. Impala males have wide, lyre-shaped horns that are 18–36 inches or longer.2
Impala males and females are similarly colored with a tan coat, reddish-brown saddle and white markings at the eyes, the inside of the ears, throat, the underside of the torso and tail. They also have black markings at the ears, tail and back feet. The darker, black-faced impala (Aepyceros melampus petersi) of southwest Africa is a less common subspecies.1
Impala are herbivores that both graze and browse for food. When grazing, they consume grass, and when browsing, they feed upon a wide variety of vegetation, including fruits, seedpods, shoots as well as leaves of trees and bushes.3
Impala are both diurnal and nocturnal, being most active immediately after sunrise and just before sunset. Female impalas and their offspring gather into herds which number from 15 to 100 individuals. The home range of a herd covers a territory that varies from 80 to 180 hectares.3 During the wet season, females become highly territorial and defend the home ranges. Young males form non-territorial bachelor herds of up to 30 individuals. During the dry season, male and female herds mix together.
Impala have a polygynous mating system, with each male mating with a number of females.2 Breeding activity spans from March through May. During this time, pregnant females live in isolation to give birth. After gestating from 190 to 200 days, a single calf is born. Shortly thereafter, the calf and the mother will rejoin the herd.3
Causes of Capture Myopathy in Impala
Capture myopathy (CM) is a condition that can arise in wild or domestic animals where muscle damage results from extreme exertion, struggle, or stress. It has also been called exertional myopathy, overstraining disease and exertional rhabdomyolysis.4 Capture myopathy can come about as the result of other natural causes of stress, such as in prey animals attempting to avoid or struggling with predator animals, but it most often occurs as a result of capture, transport or chemical immobilization.5
Capture myopathy can occur in any animal under extreme stress, although it is thought that some species may be more predisposed to it than others.6 Capture myopathy has been observed in ungulates, birds, coyotes, badgers, primates, and many other species.5 It is believed that capture myopathy can even occur in fish and amphibians.4
Clinical Signs of Capture Myopathy
When animals overexert themselves (e.g., struggling in a trap) to the extent that physiological imbalances develop and result in severe muscle damage, capture myopathy can result.5 Increased ambient temperatures and repeated chemical immobilization can increase the risk of animals suffering from capture myopathy.7 Impala, like many other animals, are adapted to escape from predators, but they are not adapted to struggle for long periods of time in human-constructed restraints.6
Symptoms of capture myopathy in impala can vary depending on the cause of exertion.5 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.7 During early onset, the clinical signs include elevated respiratory rate, heart rate, and body temperature.4,6 Body temperature increases during exertion, and higher temperatures have been associated with death due to CM. 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 In such cases, death of the animal usually follows. If it survives the acute stage of the condition, scarring of heart and skeletal muscle tissue may permanently debilitate the animal.7 If light-colored skeletal and cardiac muscle are seen upon necropsy, this is indicative of capture myopathy being the cause of death.
Preventing Capture Myopathy in Impala
Prevention is the best method of avoiding capture myopathy in impala, since there is no treatment for condition. Extra care should be taken in handling 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 impala. In the field, the remote delivery of anesthetic agents is a superior methodology to trapping an animal prior to the anesthetic event.
The team in the field should be thoroughly aware of the risks of capture myopathy and make every effort to prevent its occurrence. Impala should only be captured when necessary, and the negative effects that capture may have on the animal's health should always be considered.8 Capture methods that minimize animal stress, struggling and handling time should be utilized. The ideal methods can vary depending on the subspecies, so research can be helpful in identifying the best capture method. 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 capture myopathy in any animal.6
4Friend, M., Thomas, N. J. Field Manual of Wildlife Diseases. In: Field Manual of Wildlife Diseases, United States Geological Survey, 361-368.
5Williams, E. S., Thorne, E. T. 1996. Exertional Myopathy (Capture Myopathy). Noninfectious Diseases of Wildlife, Second Edition, 181-193 Iowa State University Press, Ames, Iowa, USA.
6Blumstein, D., et. al. The evolution of capture myopathy in hooved mammals: a model for human stress cardiomyopathy?Evolution, medicine, and public health vol. 2015,1 195-203. 21 Jul. 2015,
7Kohn, Tertius. (2013). Capture myopathy mystery.
8Businga NK, Langenberg J, Carlson L. Successful treatment of capture myopathy in three wild greater sandhill cranes (Grus canadensis tabida). J Avian Med Surg. 2007 Dec;21(4):294-8.
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