Frostbite in Camels During Capture and Chemical Immobilization

Camels are large, hoofed ruminants that are native to northern Africa and Asia; they have been long noted and valued for their ability to go for long periods without both food and water. The dromedary camel (Camelus dromedarius), also known as the Arabian camel, has one back hump; the domesticated Bactrian camel (C. bactrianus) and the wild Bactrian camel (C. ferus) have two humps. Dromedary camels were also introduced into Australia during the 19^th Century. Most of the world's camels are dromedary camels, and nearly all of these are domesticated.¹

Camels have been domesticated for approximately 3,500 years. They were used almost exclusively as pack animals on the Silk Road, the network of routes used by traders between Europe and Asia for more than 1,500 years.² This was because they could carry more weight than horses or donkeys, needed less water and were able to thrive on tough desert plants. Camels have also been used for their wool, milk, meat and leather.³

All three camel species are approximately 10 feet long and 6-1/2 feet high at the hump. Males typically weigh in at approximately 900 to 1,400 pounds; females are about 10% smaller and lighter. Camels are diurnal and spend much of their days eating. Their upper lips are split in half, with each half moving independently. This allows them to forage short grasses and plants that are very near to the ground.³

Camels can last for several months without food, and they can go a week or more without water. Their back humps store up to 80 pounds of fat, which they break down into energy when food is scarce.^2,3

As mentioned above, dromedary camels were introduced into Australia in the 1840's to assist in the exploration of inland Australia, which is similar to this animal’s native habitat. At present, there are over one million feral camels in the rangeland ecosystems of Australia. Unfortunately, these animals are negatively impacting the natural environment to a significant degree. As a result, radio-collared camels are being used in Australia to enhance population control programs.⁴The procedures involved in their capture—including chemical immobilization—carry the risk of inducing a wide range of complications.

Frostbite in Camels

Frostbite is a freezing injury that may be divided into four overlapping phases:

• Prefreeze
• Freeze–thaw
• Vascular stasis
• Late ischemic⁵

Prefreeze consists of tissue cooling with accompanying vasoconstriction and ischemia and without ice crystal formation. The freeze–thaw phase is represented by the intracellular or extracellular formation of ice crystals. This can give rise to protein and lipid derangement, cellular electrolyte shifts, cellular dehydration, cell membrane lysis, and cell death. In the vascular stasis phase, vessels fluctuate between constriction and dilation, and blood may leak from vessels or coagulate within them. The late ischemic phase results from progressive tissue ischemia and infarction from a cascade of events, including inflammation, vasoconstriction and emboli.⁵

The chemical immobilization of camels can require extended periods of immobility in the captured animal. Hypothermia is an inherent risk to any animal undergoing chemical immobilization regardless of ambient temperature, and frostbite is an even greater risk during the winter months.^6,7 While chemically-immobilized dromedary camels in their natural environment are at lower risk for frostbite, Bactrian camels (whose native environment does include periods of freezing temperatures) and any camel in a captive or zoo setting may find themselves at higher risk for frostbite.

The normal temperature of healthy camels at rest varies from about 34°C to more than 40°C.⁶ 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.

When deprived of drinking water during the summer, the camel’s daytime body temperature variations 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.

Classifications of Frostbite

Frostbite is classified into four degrees of injury, and these follow the classification schemes for thermal burn injury. Early stages of frostbite are different than frostnip, which is a superficial nonfreezing cold injury associated with intense vasoconstriction on exposed skin. Frostnip may precede frostbite, however. In these cases, ice crystals do not form within the tissue and tissue loss does not occur. Numbness and pallor resolve quickly after warming the skin.⁷

• First-degree frostbite causes numbness and erythema. A white or yellow, firm, and slightly raised plaque develops in the area of injury. There may be slight epidermal sloughing and mild edema is common.
• Second-degree frostbite injury causes superficial skin vesiculation. A clear or milky fluid will be present in superficial blisters surrounded by erythema and edema.
• Third-degree frostbite causes deeper hemorrhagic blisters, indicating that the injury has extended into the reticular dermis and beneath the dermal vascular plexus.
• Fourth-degree frostbite extends completely through the dermis and involves the comparatively avascular subcutaneous tissues, with necrosis extending into muscle and bone.⁷

It should be noted that the severity of frostbite may vary within a single extremity.

Prevention of Frostbite in Camels

Nearly all of the literature suggests that prevention is a far better methodology than treatment for frostbite, which is usually preventable but often not improved by treatment. Underlying medical problems and the chemical immobilization event itself can increase risk of frostbite, so prevention must address both health-related and environmental aspects. Frostbite injury usually occurs when tissue heat loss exceeds the ability of local tissue perfusion to prevent freezing of soft tissues. The team in the field must ensure adequate perfusion and minimize heat loss to prevent frostbite.⁷

Preventive measures to ensure local tissue perfusion include:

• Maintaining adequate core temperature
• Maintaining adequate body hydration
• Minimizing the effects of any known diseases that might decrease perfusion
• Covering the body and head to insulate from the cold
• Minimizing any blood flow restriction
• Using supplemental oxygen in severely hypoxic conditions⁸

Steps should be taken to minimize exposure of the animal’s tissues to cold, such as:

• Avoid environmental conditions that predispose to frostbite if possible (e.g., below -15°C, even with low wind speeds
• Protecting exposed skin from moisture, wind, and cold
• Avoiding perspiration or wet extremities
• Increasing insulation and skin protection
• Using chemical and/or electric warmers to maintain peripheral warmth (These should be close to body temperature before being activated and must not be placed directly against skin or constrict flow)
• Regularly checking the animal’s temperature
• Recognizing frostnip or superficial frostbite before it becomes more serious
• Minimizing duration of cold exposure^7,8

Treatment of Frostbite in Camels

If a camel’s body part is frozen in the field, the frozen tissue should be protected from further damage.⁸ A decision must be made whether to thaw the tissue. If environmental conditions are such that thawed tissue could refreeze, it is safer to keep the affected part frozen until a thawed state can be maintained. Frostbite thaws spontaneously and should be allowed to do so if rapid rewarming cannot be easily achieved.

Hypothermia frequently accompanies frostbite and causes peripheral vasoconstriction that impairs blood flow to the extremities. Mild hypothermia may be treated concurrently with frostbite injury. Moderate and severe hypothermia should be treated effectively before treating frostbite injury.^7,8

Hydration Treatment

Vascular stasis can result from frostbite injury, thus appropriate hydration and avoidance of hypovolemia are important for frostbite recovery. Intravenous normal saline should be given to maintain normal urine output. IV fluids should optimally be warmed before infusion and infused in small, rapid boluses, as slow infusion can result in fluid cooling and even freezing as it passes through tubing. Fluid administration should be optimized to prevent clinical dehydration.⁷

Low Molecular Weight Dextran (LMWD) Treatment

Intravenous low molecular weight dextran (LMWD) decreases blood viscosity by preventing red blood cell aggregation and formation of microthrombi and can be given in the field once it has been warmed. In some animal studies, the extent of tissue necrosis was found to be significantly less than in control subjects when LMWD was used, and was more beneficial if given early.⁷

The use of LMWD has not been evaluated in combination with other treatments such as thrombolytics. LMWD should be given if the animal is not being considered for other systemic treatments, such as thrombolytic therapy.^7,8

NSAIDs Treatment

Nonsteroidal anti-inflammatory drugs (NSAIDs) block the arachidonic acid pathway and decrease production of prostaglandins and thromboxanes. These can lead to vasoconstriction, dermal ischemia, and further tissue damage.⁸ No studies have demonstrated that any particular anti-inflammatory agent or dosing is clearly related to outcome, however. One rabbit ear model study showed 23% tissue survival with aspirin versus 0% in the control group.⁷ However, aspirin theoretically blocks production of certain prostaglandins that are beneficial to wound healing, which may or may not be of concern following a chemical immobilization event.

¹britannica.com.

²nationalgeographic.com.

³spana.org.

⁴pestsmart.org.au.

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.

⁶Schmidt-Nielsen, K., et. al. Body Temperature of the Camel and Its Relation to Water Economy. American Journal of Physiology. 31 Dec 1956.

⁷McIntosh, S., et. al. Clinical Practice Guidelines for the Prevention and Treatment of Frostbite: 2019 Update. Wilderness Medical Society Clinical Practice Guidelines, Volume 30, Issue 4, Supplement S19-S32, December 01, 2019.

⁸McIntosh, S.E., et. al. Wilderness Medical Society practice guidelines for the prevention and treatment of frostbite: 2014 update.Wilderness Environ Med. 2014; 25: S43-S54

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