Capture Myopathy in Nyala Antelope
The nyala is a dense forest- and thick bush-dwelling antelope that is found in the eastern part of southern Africa. There are two subspecies of nyala: The lowland nyala (Tragelaphus agasi), and the mountain nyala (Tragelaphus buxtoni).These antelope are generally uncomfortable in open spaces since they do not have the explosive running ability of other African antelope. Thus, they are most often seen at water holes, where they typically live alone or in small family groups of up to 10 individuals.1
Female nyala have a chestnut-colored, shaggy coat that is marked with white vertical stripes and spots on the flanks. Rams appear more charcoal grey in color and have long, inward curved horns and a white chevron on the face. They have a ridge of long hairs along their undersides, and a mane of thick, black hair from the head along the spine to the hindquarters.2
Nyala feed by both grazing and browsing and will feed on leaves, fruit and flowers. The variety in their diet is believed to be one of the factors that has contributed to their survival as a species.1 Nyala are elusive and more easily seen at night. They are not territorial, with both sexes having overlapping home ranges.
Capture Myopathy in Nyala
Capture myopathy (CM) is an extremely serious condition that can occur in wild animals when muscle damage results from extreme exertion, struggle, or stress. It is also known as exertional myopathy, overstraining disease and exertional rhabdomyolysis.3 Most often, capture myopathy 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.4
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 natural temperament and physiological characteristics.5 Capture myopathy has been most widely studied in ungulates and birds, although it is believed it can potentially affect any captured wild animal. It is believed that capture myopathy can even occur in fish and amphibians.3
Clinical Signs of Capture Myopathy
Nyala, like other prey animals, are adapted to escape from predators, but they are not well-adapted to struggle for long periods of time in human-constructed restraints.5 As prey animals, predation stress comes into play when they are captured, whereas other animals (e.g., large carnivores) might respond with more aggression. When animals overexert themselves to the extent that physiological imbalances develop and result in severe muscle damage, capture myopathy results.4 Increased ambient temperatures and repeated chemical immobilization can increase the risk of animals suffering from capture myopathy.6
Source/Credit: Oxford University Press
Clinical signs of capture myopathy in nyala can vary depending on the species and the cause of exertion.4 The method of capture and restraint is also a determinant in occurrences of capture myopathy. 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.6 The clinical signs during early onset include elevated respiratory rate, heart rate, and body temperature.3,5 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.6 Muscle spasms, stiffness and lameness are also clear signs of CM. An animal may 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.4-6 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.6 Upon necropsy, light-colored skeletal and cardiac muscle is indicative of capture myopathy being the cause of death.
Preventing Capture Myopathy in Nyala
There is no treatment for capture myopathy, so prevention is the best method of avoiding this condition. Care should be taken in 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 nyala. In these cases, the remote delivery of anesthetic agents is a superior methodology to trapping the antelope prior to the anesthetic event.
The capture team should be thoroughly aware of the risks of capture myopathy in nyala and make every effort to prevent its occurrence. Nyala should only be captured when necessary, and the negative effects that capture may have on the animal's health should always be considered before beginning a capture or initiating an anesthetic event.7 Capture methods that minimize animal stress, struggling and handling time should be utilized. Appropriate methods may vary depending on the subspecies, so research can be helpful in identifying the ideal 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.5
3Friend, M., Thomas, N. J. Field Manual of Wildlife Diseases. In: Field Manual of Wildlife Diseases, United States Geological Survey, 361-368.
4Williams, 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.
5Blumstein, 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,
6Kohn, Tertius. (2013). Capture myopathy mystery.
7Businga 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. doi: 10.1647/2005-013R1.1. PMID: 18351009.
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