Hypothermia and Hyperthermia in Camels During Chemical Immobilization
It is likely that few animals are as well-recognized around the world as the camel. There are three recognized species of camel: the dromedary camel (Camelus dromedarius), which is the most widespread; the Bactrian camel (C. bactrianus)and the wild Bactrian camel (C. ferus). The dromedary camel is also known as the Arabian camel, and nearly all of these are domesticated.1 Camels are native to northern Africa and southwestern Asia, and were introduced into Australia nearly two centuries ago.
The dromedary camel has one back hump, while the domesticated and wild Bactrian camels have two humps. Camels have been domesticated for approximately 3,500 years and have been used as pack animals that can carry large loads (over 100 lbs.) for up to 25 miles a day.2 Camels have also been used for their wool, milk, meat, leather, and dung.2
Camels are camelids, the family that includes camels, alpacas and llamas. They are members of the biological family Camelidae, and the only family in the suborder Tylopoda.1 Camels differ from other ruminants such as cattle in a number of ways:
- They have a three-chambered digestive tract rather than a four-chambered one.
- Their upper lip is split in two, with each part being under separate muscle control.
- They also have an isolated incisor in the upper jaw.
- Their red blood cells are oval shaped, which helps to facilitate their flow when the animal is dehydrated.
- Their red blood cells are also more stable in order to withstand high osmotic variation without rupturing when these animals drink large amounts of water (sometimes up to 30 gallons at one sitting).2,3
Adult camels reach up to 10 feet long and 6-1/2 feet high at the hump. Males weigh approximately 900 to 1,400 pounds, with females being 10% smaller and lighter. Their color is light brown to medium gray. Bactrian camels are darker and more stocky, and have more hair than wild Bactrian camels.2 All camels have heavy eyelashes which protect their eyes from blowing sand, and their nostrils can be squeezed shut.
The camels’ split upper lip allows them to forage very near to the ground. Their lips can break off and eat tough vegetation such as thorns or salty plants.3 Camels can go for a week or more without water, and a camel can last for several months without food. Their humps can store up to 80 pounds of fat, which camels break down into water and energy when food is not available.2,3
Stress, Hypothermia and Hyperthermia
Despite the high level of domestication of many camels and their amenable nature, their capture can be a highly stressful event which has the potential to cause capture-induced hypothermia or hyperthermia. Either of these complications 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 (possibly leading to dehydration events), increased oxidative stress and death.4 It has also been called one of the primary indications for the development of capture myopathy.
Mechanisms underlying the increase in body temperature during capture-induced hypothermia and hyperthermia are not fully understood, but 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 severe hyperthermia.5
Dromedary camels were 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, which are causing significant damage to the natural environment. Radio-collared camels are being used today in Australia to enhance population control programs.6 The attendant procedures—which involve chemical immobilization—carry the risk of inducing a wide range of complications in these animals, including hypothermia and hyperthermia.
Thermoregulation in Camels
The normal temperature of healthy camels at rest varies from about 34°C to more than 40°C.7 Due to the harsh environments that camels occupy, they have evolved with a unique ability for thermoregulation. This is referred to as adaptive hypothermia, or an ability to cool their bodies to avoid hyperthermia. It has also been observed that male dromedary camels in rut have cooler body temperatures in the beginning of the day, which may be a factor in reproductive success.8
In summer, the camel’s daytime body temperature variations when deprived of drinking water may exceed 6°C, but in animals with access to water, the variations are similar to those found during other seasons.7 These wide variations in temperature are tolerated by the camel, whereas in other animals, if body temperatures exceed more than 2 to 3 degrees higher than lower than the norm during an immobilization event, there is serious cause for concern.
Preventing Hypothermia and Hyperthermia in Camels
The measurement of body temperature should be standard procedure during all anesthetic events involving camels, and thermometers should be able to read over a wide temperature range. While hypothermia is more common in small animals because of the large surface area-to-volume ratio, instances of both hypothermia and hyperthermia have both been reported during the capture of camels. Some drugs used in chemical immobilization are known to suppress normal thermoregulatory mechanisms, thereby causing hypothermia or hyperthermia. Hyperthermia however, is also common immediately after the immobilization of both captive and free-ranging hoofstock due to excitement and struggling while darting.9-11
Monitoring core body temperature is essential in camel anesthesia,9 and intubation has been widely recommended for any anesthetized camel that needs to be transported or anesthetized for greater than twenty minutes.4 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 camel anesthesia in wildlife and captive care.10
Treating Hyperthermia in Camels
Given that capture-induced hyperthermia in a camel may be severe, one method recommended for improving their chances for survival is to physically cool captured animals. Recommendations for cooling captured camel include placing the animals in the shade and dousing them with water using portable mist sprayers, followed by rapid intravenous (IV) fluid therapy.9 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.10,11
Ice packs were also reported to have restored the body temperature of hyperthermic animals to pre-capture levels.9 The authors point out however, that since carrying water is far less cumbersome and difficult than transporting and maintaining ice-packs in the field, thus they recommend that water-dousing is the most practical and effective first intervention for cooling an camel with capture-induced hyperthermia.
Treating Hypothermia in Camels
Hypothermia during anesthetic events is a common adverse effect of anesthesia in many species. In particular, smaller animals are susceptible to hypothermia during anesthetic events, but even large hoofstock and even carnivores can be affected.10 Having thermal support available (e.g., external heating devices) during and after anesthesia is prudent. In most cases, the time of recovery from anesthesia will be 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
In cases of mild hypothermia, shivering may be the only outward symptom. As hypothermia increases in severity, the other listed can symptoms become evident. The animal’s vital signs are likely to become increasingly erratic as its body goes into heat conservation mode.9 At this juncture, the animal’s body is trying to keep its vital organs functioning by restricting the blood flow from other parts of the body.
Water bottles filled with warm water and placed around the animal’s body can be used to reverse hypothermia. 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.10 Returning the animal to a warm environment (if possible) and/or using heat lamps (if available) can also be helpful.
4Ball, L. Camel Anesthesia. Wiley Online Library, 25 July 2014.
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.
7Schmidt-Nielsen, K., et. al. Body Temperature of the Camel and Its Relation to Water Economy. American Journal of Physiology. 31 Dec 1956.
8Grigg, Gordon & Beard, Lyn & Dörges, Birgit & Heucke, Jürgen & Coventry, Jocelyn & Coppock, Alex & Blomberg, Simone. (2009). Strategic (adaptive) hypothermia in bull dromedary camels during rut; could it increase reproductive success? Biology letters. 5. 853-6. 10.1098/rsbl.2009.0450.
9Arnemo, 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.
10Arnemo, Jon & Kreeger, Terry. (2018). Handbook of Wildlife Chemical Immobilization 5th Ed. Sunquest Publishing, 2007.
11Richardson, D. Journal of Mammalogy, Volume 56, Issue 3, 29 August 1975, Pages 698–699.
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