Hypothermia and Hyperthermia in Kudu Antelope During Chemical Immobilization
Antelope comprise around 90 of the approximately 140 known species of the Bovidae family (e.g., sheep, goats, domesticated cattle). Antelope belong to the order Artiodactyla, the most distinctive feature being their even number of hooves. The kudu is a large African antelope that consists of two subspecies: the greater kudu (Tragelaphus strepsiceros),and the lesser kudu (Tragelaphus imberbis). The greater kudu is second in size to the eland, Africa’s largest antelope. Both of the subspecies have stripes and spots on their bodies and a chevron of white hair between the eyes.1 The males have long, spiraling horns, with the horns of the greater kudu growing as long as six feet. In both subspecies, the females are substantially smaller than the males.
The greater kudu inhabits the forested areas and dense brush of southern Africa; the more elusive lesser kudu is common in the arid lowland thornbush of northeast and East Africa.2 Both kudus forage on a wide variety of trees, shrubs, vines, herbs, seedpods, fruits and grasses.1
Stress, Hypothermia and Hyperthermia
According to the available literature, each species of antelope has its own anesthesia recommendations. Many species have been reported as notoriously difficult to effectively anesthetize due to their diverse individual responses to anesthetic agents.
The capture of kudu is a highly stressful event which has the potential to cause capture-induced hypothermia or hyperthermia, either of which can result in morbidity or mortality. The severity of the capture-induced hyperthermia has been associated with the likelihood of organ damage, alterations in electrolyte balance, increased oxidative stress and death.3 It has also been called one of the primary causes for the development of capture myopathy.
While the mechanisms underlying the increase in body temperature during capture-induced hypothermia and hyperthermia are not fully understood, one factor appears to be the sympathetic stress response. Even with animals engaging in low levels of activity during capture with mild ambient temperatures can develop hyperthermia.4
The average body temperature for most antelope species typically average between 35o -42o C.1,6 When these exceed more than 2 to 3 degrees higher or lower than the norm during an immobilization event, there is cause for concern and intervention may be required. In the case of capture-induced hypothermia, outward signs may also be evident (see below).
Preventing Hypothermia and Hyperthermia
Measurement of body temperature should be standard procedure during all anesthetic events, and thermometers should be able to read over a wide temperature range. Hypothermia is more common in small animals because of the large surface area-to-volume ratio, but instances of both hypothermia and hyperthermia have both been reported during the capture of antelope. Some drugs used in chemical immobilization are believed to suppress normal thermoregulatory mechanisms, thereby causing hypothermia or hyperthermia. Hyperthermia however, is also common immediately after immobilization of both captive and free-ranging antelope due to excitement and struggling while darting.3-5
Monitoring core body temperature is essential in antelope anesthesia,6,7 and intubation has been widely recommended for any anesthetized antelope that needs to be transported or anesthetized for greater than one hour. Until the more recent use of formulated drugs (e.g., combinations of α2-agonists such as medetomidine, detomidine, xylazine and their reversal agents), opioids were the mainstay of antelope anesthesia in wildlife and captive care.5
Treating Hyperthermia in Kudu
One recommended method for improving an antelope’s chances for surviving severe hyperthermia is to physically cool the captured animal. Recommendations for cooling captured antelope include placing the animal in the shade and dousing it with water using portable mist sprayers, followed by rapid intravenous (IV) fluid therapy.6 In animals with body temperatures greater than 41°C, the use of cold water enemas and intravenous infusion of cold Ringer’s lactate has been recommended.5,7
Ice packs have also been used to restore the body temperature of hyperthermic animals to pre-capture levels.5 Since carrying water is far less cumbersome and difficult than transporting and maintaining ice-packs in the field, some have recommend that water-dousing is the most practical and effective first intervention for cooling an antelope with capture-induced hyperthermia.
Treating Hypothermia in Kudu
Hypothermia during anesthetic events is a common adverse effect of anesthesia in many species; smaller animals are susceptible to hypothermia during anesthetic events, but large hoofstock and even carnivores can be affected.7 Having thermal support available in the form of external heating devices during and after anesthesia is prudent. In general, the time of recovery from anesthesia is typically longer in case of injectable anesthesia rather than inhalant anesthesia.
In addition to abnormally low body temperature, signs of hypothermia can include:
- Shivering
- Stiff muscles
- Pale or gray gums
- Fixed and dilated pupils
- Low heart and breathing rate
With mild hypothermia, shivering may be the only outward symptom. As hypothermia increases in severity, the other usually symptoms become evident. The animal’s vital signs are likely to become increasingly erratic as its body goes into heat conservation mode.3,5 At this point, the animal’s focus is on keeping its vital organs working by restricting the blood flow from all other parts of the body.
Hypothermia can be reversed through the use of water bottles filled with warm water and placed around the animal’s body. External heating devices may also be used, although some of the literature states that heating pads should be used with care, as it is easy to burn an animal’s skin.8 Returning the animal to a warm environment and/or using heat lamps can also be helpful.
3Ball, L. Antelope Anesthesia. Wiley Online Library, 25 July 2014.
4Sawicka, J. et. al. Efficacy of Different Cooling Methods for Capture-Induced Hyperthermia in Antelope. (2015).
5Haskins, S.C. (1995). Thermoregulation, hypothermia, hyperthermia. In: SJ. Ettinger. & EC. Feldman (Eds), Veterinary internal medicine (4th edition) (pp. 26–30). Philadelphia. U.S.A. W.B Saunders Company.
6Arnemo, J., Fahlman, A. (2008). Biomedical protocols for the free-ranging brown bears, gray wolves, wolverines and lynx. Hedmark University College, Norway and Swedish University of Agriculture Sciences, Sweden.
7Arnemo, Jon & Kreeger, Terry. (2018). Handbook of Wildlife Chemical Immobilization 5th Ed. Sunquest Publishing, 2007.
8Richardson, D. Journal of Mammalogy, Volume 56, Issue 3, 29 August 1975, Pages 698–699.
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