Biology

Cervids are Artiodactyla belonging to the family Cervidae. Within this family there are 4 sub-families:

 Cervinae (deer and elk)

 Hydropolinae (Chinese water deer)

 Muntiacinae (muntjac)

 Odocoileinae (deer and moose)

The species within each sub-family that practitioners are most likely to encounter are: Cervinae

 (Dama dama) European Fallow deer

 (Cervus nippon) Sika Deer

 (Cervus elaphus) Red Deer, Wapiti or North American Elk Muntiacinae

 (Muntiacus muntjak) Indian Muntjac / (Muntiacus reevesi) Reeve's Muntjac Odocoileinae

 (Alces alces) Moose or European Elk

 (Odocoileus hemionus) Mule Deer

 (Odocoileus virginianus) White-tailed Deer

 (Rangifer tarandus) Reindeer or Caribou

Physiological Characteristics

Antlers are seen in male deer only, except for reindeer or caribou where both sexes have antlers. Generally antlers increase in size as the animal's age. While antlers are growing they are protected by velvet. The Velvet is very vascular and sensitive to the touch. Antlers are shed annually after rut in males or after birthing in female reindeer/caribou. In castrated animals antler growth and shedding is abnormal unless males are castrated before the onset of puberty. The growing base of the antler is referred to as the pedicle. In species that have small antlers, such as muntjac and Chinese tufted deer the males have elongated upper canine teeth that appear as tusks.

Scent glands are present on the face (pre-orbital), legs (metatarsal) and feet (inter-digital). The gall bladder is absent and the mammae consist of two pair of teats. The dental formula of cervids is: I 0/3, C 0–1/1, PM 3/3, M 3/3. The summer coat in adult Axis and Fallow deer is spotted as are the fawns in some species

Nutrition

In the wild deer vary from concentrate selectors to partial grazers. The majority of species are intermediate feeders consuming browse and grasses. Captive deer may be pastured, or fed hay, browse and concentrates, depending on feeding strategies, production goals and season. Concentrate supplements that contain different protein and fiber levels are commercially available. Temperate species will store fat during the spring and summer. Animals, especially males, will decrease food intake during the breeding season (rut). Copper deficiency as a primary deficiency or as a secondary molybdenum excess is not uncommon in captive and free ranging cervids. Clinically poor growth, dry, poor quality hair coats with abnormal color, antler malformations, and osteoporosis has been observed. If copper deficiency is suspected liver copper levels should be monitored. Treatment or prevention can be achieved with orally administered copper oxide needles or trace mineral supplements.

Handling Techniques / Chemical Restraint

Manual Restraint

Hand restraint can be performed on young or very tractable animals. Handlers should be aware that deer hooves are sharp and can cut clothing and skin. A properly set up chute and squeeze system is often the most economical, efficient and safest method for handling cervids. A standard squeeze chute (with or without a head catch) is utilized for larger animals such as elk. A drop floor chute (where after entering the chute, the floor is dropped leaving the animal suspended) is appropriate for deer. The drop floor chute decreases struggling and allows the animal to be safely handled with minimal stress. The width of the drop floor chute can be adjusted to accommodate a variety of species. Most chute systems allow access to the front and rear of the animal and also the back and legs, thus enabling the producer or clinician to perform routine husbandry procedures, disease testing and reproductive manipulations. The tops of the chutes are wide to allow for antlers. Once in the chute the animal should be blind folded to reduce visual stimulation. If the head, ears, antlers are manipulated then a halter can be applied and the head tied. Local anesthetic, sedation or immobilization agents can be administered within the chute. The design of the sorting and holding pens and runways leading to the chute should incorporate principles developed for safely moving farmed deer. A circular pattern layout with, non-slip solid footing, adequate lighting and appropriate visual barriers are recommended for decreasing stress during the handling of any grazing species. Any unnecessary noise should be minimized and lighting should be adequate but muted. Elevated catwalks facilitate animal handling but should never go over the top of chute areas as animals will become distracted by what is above them and reluctant and fearful to move forward. Animals should be restrained and handled gently but firmly and it is important that they feel secure and balanced in the squeeze.

Pre-Immobilization Considerations

If the procedure is elective animals should be fasted for 24 hours with no water for last 12 hours to decrease the incidence of regurgitation and bloat. In a free-range setting this may be difficult. Deer have a strong flight response, and can easily become over heated. Avoid immobilizing during high ambient temperatures. As the ambient temperature increases it becomes more difficult for animals to dissipate heat and ideally a capture or immobilization should be planned for a cool, cloudy day with temperatures less than 77°F (25°C).

Positioning

During the immobilization care should be taken to protect the airway by maintaining the animal in sternal recumbency if possible (which decreases the pressure of the abdominal viscera on the diaphragm) and by placing the head up but with the nose and mouth below the level of the ears to allow saliva or regurgitated rumen contents to drain. If the terrain is not level the animal should be positioned with the head pointed up hill to decrease pressure from the abdominal viscera. Deer can be "silent" regurgitators and inhalation pneumonia can occur post immobilization. Antlers can complicate head placement but make useful handles for positioning the head. Be aware that antlers in velvet are a living part of the animal. The velvet contains nerves and a rich supply of blood vessels and should be handled gently to avoid damage.

Monitoring

Anesthetized deer are prone to hypoxemia. Factors that exacerbate the risk of hypoxemia include the use of alpha-2 agonists and positioning the animal in dorsal or lateral recumbency. Hypoxemia, if severe and left untreated can lead to cardiac arrhythmias, organ function compromise, adverse metabolic changes such as capture myopathy, and even death. It is strongly advised that supplemental oxygen is provided and the flow rate adjusted to maintain the SpO₂ level above 95%. Nasal O₂ can be delivered with a small non-cuffed 3–4 mm endotracheal tube or soft pliable tubing such as is used for IV fluid administration that is advanced to the level of the medial canthus of the eye. A flow rate of 6 to 8 L/min is usually adequate for smaller species such as white-tail deer; larger species such as elk may require 10 L/min.⁵

Hyperthermia can also occur during immobilization of cervids, especially free-ranging animals and body temperature should be monitored throughout the procedure. An animal's internal temperature may increase from physical exertion as well as psychological stress and fear, and the animal's ability to thermoregulate is decreased by immobilization agents such as tranquillizers and sedatives. Hyperthermia may predispose the animal to metabolic complications such as capture myopathy, or if the body temperature increases above 109°F, (43°C) death may occur.

Emergencies

Capture myopathy is a syndrome that is not infrequently seen during capture and handling events in deer and is analogous to exertional rhabdomyolysis in humans and horses. However the pathogenesis of capture myopathy not only includes muscular activity but the sympathetic nervous and adrenal systems as well as perception of fear. Capture shock is the acute manifestation of capture myopathy in which the animal develops tachypnea, tachycardia, hyperthermia, hypotension and depression usually followed by death within 1 to 6 hours. Less acute syndromes occur from the sequela to muscle necrosis and metabolic abnormalities and include severe myoglobinuria with resulting renal failure or acute rupture of the gastrocnemius muscle. Treatment is usually unsuccessful and prevention is the most effective way to manage capture myopathy. Vitamin E and selenium levels in the diet have been shown to affect the incidence of capture myopathy in captive white tail deer.

Immobilization drugs and dosages used in cervids.^1,5

All dosages are listed as Mg/Kg unless otherwise noted.
Captive farmed deer may require a much lower dose than tame, farmed deer. Excited animals may require the upper end of the dose range.

Concentrated forms of immobilizing agents - ketamine HCL (200 mg/ml), xylazine HCL (300 mg/ml), medetomidine HCL (20 mg/ml), and antagonists - yohimbine HCL (10 mg/ml), and tolazoline HCL (200 mg/ml) can be purchased through ZooPharm, Inc., Fort Collins, CO, USA (www.ZooPharm.net).

Antagonists

To reverse xylazine either yohimbine at 0.125–0.2 mg/kg, given ½ IV and ½ IM or tolazoline at 2.0–4.0 mg/kg, slowly IV or ½ IV and ½ IM can be used. To reverse medetomidine, atipamezole can be administered at a 3–5:1 ratio of atipamezole to medetomidine. If a combination of dissociatives and alpha-2 agonists have been used then it is advisable to wait a minimum of 30 minutes after giving ketamine or Telazol® before administering the alpha-2 antagonist.

Viral Diseases

Malignant Catarrhal Fever is caused by the herpes virus (BHV-3) (AHV-1), (OHV-2). Many cervid species are susceptible and sudden death can be seen in sensitive species. Clinical signs include, fever, ocular discharge, corneal opacity, dysentery and neurological signs. Diagnosis is by clinical signs or characteristic lesions seen on histopathology. Prevention is achieved by separating deer from breeding cattle, alcelaphine species, and sheep and goats.

Blue Tongue (BT) / Epizootic Hemorrhagic Disease Viruses (EHDV). These closely related orbiviruses are transmitted by Culicoides midges. White-tail deer are extremely susceptible to EHDV and suffer high morbidity and mortality. Outbreaks are commonly seen in the late summer or fall when the midges are active. Clinical signs include fever, small hemorrhages or bruises in the mouth and nose, swelling of the head, neck, tongue and lips. At necropsy pulmonary edema, hemorrhagic lesions in many tissues, (including the base of the pulmonary artery which is the considered the "classic" lesion for hemorrhagic disease), vasculitis and erosions within the rumen. Diagnosis is by serological testing in conjunction with virus isolation

Bacterial Diseases Clostridial Diseases

Tetanus (C. tetanus), blackleg (C. chauvoei), clostridial enterotoxemia (C. perfringens type D), and malignant edema (Clostridium spp.) have been reported in captive deer. The incidence, clinical signs, diagnosis, treatment and prevention are similar to other ruminant species.

Tuberculosis (Mycobacterium bovis)

In U.S. primarily a disease of captive deer, although has spread in two states to wildlife. Clinical signs include enlarged lymph nodes, respiratory signs, and emaciation. Usually don't see fulminating pulmonary disease in deer as is seen commonly in cattle. Lymph nodes of the head may be infected. Diagnosis using the single cervical or comparative cervical tuberculin test is currently the official tests recognized by the U.S. Department of Agriculture. Tuberculin testing of individuals or herds is required for most interstate movement. Treatment should not be attempted.

Johne's Disease (Mycobacterium avium paratuberculosis)

Infection is usually seen in young animals, 12–18 mos. and has been reported in both captive and free-ranging deer. Clinical signs include chronic weight loss and "unthrifty" appearance. Diarrhea may not be present. Hematological evaluation may reveal hypoproteinemia with little other abnormalities. Diagnosis by fecal culture is the gold standard. Serological testing (ELISA and AGID) may be useful for herd screening. Animals with clinical signs compatible with Johne's disease should have cultures and histopathology of lymph nodes and small intestine taken at necropsy. There is no treatment

Brucellosis (Brucella abortus / B. suis)

Found in both captive and free-ranging cervids. Brucella abortus can cause mid to late term abortions, metritis, and orchitis. Brucella suis has been reported in caribou, and causes hygromas in joints, internal granulomas, orchitis, and metritis. Diagnosis is by serological testing or culture and culling of infected animals is recommended

Internal Parasites

Parelaphostrongylus tenuis, Elaphostrongylus cervi and E. rangiferi

Mature worms are in the muscles and nervous tissue of deer. The parasites are adapted to specific host species and to geographical distributions and infections in aberrant hosts (deer or other ruminants) can cause severe disease. The white-tailed deer is the normal host of P. tenuis. Transmission requires an intermediate host which is a terrestrial snail. The larvae migrate from the rumen to the spinal cord of the non-specific host leading to neurological signs and death. First stage larvae can be found in feces utilizing a Baermann's test. Prevention is the primary method to control infection as treatment is usually unrewarding.

Fascioloides magna

White-tailed deer are the natural host. The intermediate host is an aquatic snail. Minor liver pathology in found in natural host species but extensive liver migration and liver pathology has been found in elk, moose and other species of deer.

Gastrointestinal Nematodes and Protozoa

Ostertagia spp., Trichostrongylus spp., Haemonchus spp., Cooperia spp., Capillaria spp., Nematodirus spp., Strongyloides spp., and Eimeria spp. have been reported in cervids. Anthelmintic drugs and dosages that are used in other small ruminants are appropriate for deer and treatment regimens should be based on results of fecal exams.

External Parasites

Mites of the genus Psoroptes, Chorioptes, and Demodex can infect cervids. Both biting lice (Mallophaga spp.) and sucking lice (Anoplura spp.) have also been found on captive deer.

Handling Equipment

 JK Reid, 7647 Wellington County Road 10, R.R.#1 Moorefield, ON, Canada, www.jkreid.com

 JDL Longhorn Inc. 39637 260th Ave., Pittsfield, IL, 62363, USA www.jdlsalesinc.com (VIN editor: link was not accessible on 12/08/11)

References

1.  Kreeger TJ. Handbook of Wildlife Chemical Immobilization. Wildlife Pharmaceuticals, Inc., Fort Collins, CO, USA. 1999.

2.  Flach E. Cervidae and Tragulidae. In: Fowler ME, Miller RE, eds. Zoo and Wildlife Medicine: Current Therapy, 5, WB Saunders, Philadelphia, Pennsylvania. 2003:634–649.

3.  Manning EJB, Collins MT. Paratuberculosis in zoo animals. In: Fowler ME, Miller RE, eds. Zoo and Wildlife Medicine: Current Therapy, 5, WB Saunders, Philadelphia, Pennsylvania. 2003:612–616.

4.  Haigh JC. Management practices to minimize infectious and parasitic diseases of farmed and ranched cervids and bison. Wildlife husbandry and diseases. Scientific and technical review. Paris, France, Office International Des Epizooties, 1996;15(1):171–181.

5.  Caulkett N, Haigh JC. Deer (Cervids) In: West G, Heard D, Caulkett N, eds. Zoo Animal and Wildlife Immobilization and Anesthesia. Blackwell Publishing, Ames, Iowa. 2007:607–612.