Treatment of exotic species

INTRODUCTION

The presentation of various exotic species of animal to the veterinary surgeon for treatment is now an everyday occurrence. The care and handling needed by these animals differ from that required by dogs and cats in the following ways:

• Response to human contact – most exotic species have an innate fear of humans and any form of human contact is likely to induce a degree of distress. Certain individual animals, e.g. some rabbits, guinea pigs and ferrets, may tolerate or actively seek human company but to most the instinct is to run, or in some cases, to attack. This must be taken into consideration when providing nursing care – observe the patient unobtrusively, avoid unnecessary physical contact and be aware that most ‘exotics’ do not appreciate the sound of the human voice.

• Methods of restraint – some species are small and agile and can be easily injured by inept handling while others have wings, providing a different means of escape. Reptiles are ectothermic, depending on their environment for heat and energy – they may suddenly become very active in the warmth of your hands. All are capable of causing injury to the ill-prepared handler.

• Reaction to anaesthesia – the term ‘exotics’ covers a wide range of species showing an equally wide range of differing responses to anaesthetic agents. It is not the brief of this chapter to describe the action of each anaesthetic agent but veterinary nurses must ensure that they are familiar with the clinical parameters and the reflexes that can be used to monitor the level of anaesthesia.

By understanding that the nursing care required by exotic species is different from that normally given to dogs and cats, the veterinary nurse can significantly increase the chances of recovery and survival of the exotic patient.

THE RABBIT – ORYCTOLAGUS CUNICULUS

For biological data, see Table 13.1.

Table 13.1

Biological data relating to rabbits and small rodents

	Chinchilla	Gerbil	Guinea pig	Golden hamster	Mouse	Rat	Rabbit
Lifespan (years)	10–12	3–4	4–8	2–3	2–3	3–4	5–12
Adult weight	400–600 g	50–60 g	750–1000 g	80–120 g	20–40 g	400–800 g	1–8 kg
Body temperature (°C)	38–39	37.4–39	38.6	36.2–37.5	37.5	38.0	38.3–39.4
Respiratory rate (breaths/min)	40–80	90–140	90–150	70–80	100–250	70–150	35–60
Pulse rate (beats/min)	100–150	250–500	130–190	280–412	500–600	260–450	130–325
Oestrus cycle (days)	41 Seasonally polyoestrous	4–6	15–17	4	4–5	4–5	No regular cycle. Induced ovulator
Age at puberty	8 months	10 weeks	M 8–10 weeks F 4–5 weeks	6–10 weeks	6–7 weeks	8–10 weeks	4–6 months
Gestation period (days)	111	24–26	63	16	19–21	20–22	28–32
Development of young at birth	Precocial	Altricial	Precocial	Altricial	Altricial	Altricial	Altricial
Weaning age	6–8 weeks	24–27 days	2–3 weeks	3–4 weeks	3–4 weeks	3–4 weeks	4–6 weeks
Type of diet	Herbivorous Coprophagic	Omnivorous Coprophagic	Herbivorous Need vitamin C	Omnivorous Coprophagic	Omnivorous Coprophagic	Omnivorous Coprophagic	Herbivorous Coprophagic
Natural behaviour	Nocturnal Social	Nocturnal Monogamous	Diurnal Social	Nocturnal Solitary	Nocturnal Social	Nocturnal Social	Crepuscular Social

HANDLING AND RESTRAINT

Procedure: To restrain a rabbit

1. Action: Observe the rabbit before handling.

Rationale: To assess the nature and condition of the rabbit – if it is aggressive you may need to ask for assistance. Restraint may cause respiratory arrest in dyspnoeic animals. Severe stress and fear may lead to cardiac arrest.

2. Action: Rabbits should be handled gently but firmly.

Rationale: Rabbits have an innate fear of humans, whom they perceive as predators.

3. Action: Talk quietly to the rabbit and approach from behind the head.

Rationale: The eyes of the rabbit are placed on each side of the head, providing good lateral vision, but very poor backwards vision. There is no need to offer a hand for the rabbit to sniff – it may be mistaken for food.

4. Action: If the animal is fractious, grasp by the scruff and support the weight with one hand under the hindquarters (Fig. 13.1).

Rationale: Never pick a rabbit up by the ears! The hind legs must be supported at all times. Rabbits have a fragile skeleton and large lumbar muscles. By struggling or kicking, rabbits can easily break their hind legs or dislocate or fracture their spines, resulting in paralysis. They also have large claws, which may injure you.

5. Action: More docile rabbits may be restrained by placing one hand under the thorax, gripping the forelegs between the thumb and forefingers of that hand. Support the hind end with your other hand.

Rationale: Some rabbits may resent being scruffed. The back should be kept in a normal curved position to avoid spinal fracture.

6. Action: To carry the rabbit, tuck the head and front feet under your upper arm and support the body along your forearm (Fig. 13.2).

Figure 13.2 Carrying a rabbit with the head tucked under the arm.

Rationale: Keeping the rabbit close to your body avoids the risk of it kicking and scratching you. Keeping its head in the dark makes the rabbit relax.

7. Action: A large towel can be used as an additional means of restraint. Place the rabbit on the opened towel with its head projecting from one side. Wrap the towel around the body, covering the feet and leaving the head exposed (Fig. 13.3).

Figure 13.3 A large towel wrapped securely around the rabbit can be very helpful for restraint.

Rationale: Covering the feet protects the handler from injury while the head is available for examination and administration of medicines.

8. Action: An excessively aggressive rabbit may be removed from a cage by throwing a towel over the animal and covering it completely. The rabbit can be unwrapped when it is safely on the examination table.

Rationale: Care must be taken to avoid injuring the rabbit or being injured yourself.

Procedure: To sex a rabbit

1. Action: Hold the scruff of the rabbit and support its weight by placing one hand under its hindquarters.

Rationale: The rabbit must be held firmly to avoid possible injury to itself or to you.

2. Action: Gently lower the rabbit on to an examination table so that it lies in dorsal recumbency. Maintain your hold on the scruff and tilt the animal so that it is almost upside down.

Rationale: In this position the rabbit is almost ‘hypnotized’ and is easier to examine.

3. Action: Using your forefinger and middle finger, apply pressure to the vent area just in front of the anus. It may be easier for the examination to be carried out by an assistant while you maintain a firm hold on the rabbit (Fig. 13.4).

Figure 13.4 Sexing a rabbit. A, C, Male rabbit; B, D, female rabbit.

Rationale: In both sexes the area will protrude. Bucks (male) under 5 weeks old will show a blunt white tube without a central line while older bucks will show a pink tube with a pointed end that resembles a bullet; the doe (female) has a central slit-like opening to the vulva with a band of pink tissue on either side.

N.B.: Young rabbits are difficult to sex up to the age of about 3 weeks. Adult bucks have large scrotal sacs which are visible lateral and cranial to the penis. The testes can be retracted. Adult does often have a prominent fur-covered dewlap under the chin.

ADMINISTRATION OF MEDICINES

Procedure: To administer fluids or liquid medication

1. Action: Place the rabbit in sternal recumbency on an examination table and wrap it in a towel as previously described (Fig. 13.3).

Rationale: Using this method the legs are restrained but the head is exposed, providing access to the mouth.

2. Action: Take the head in one hand and tilt slightly to one side.

Rationale: In this position, one corner of the mouth is uppermost.

3. Action: Using a syringe of an appropriate size containing the liquid medication, place the nozzle into the uppermost corner of the mouth.

Rationale: Avoid using large syringes as they are difficult to control.

4. Action: Apply gentle pressure to the syringe and give the medication. Allow time for the rabbit to swallow.

Rationale: Give fluid in boluses of 0.25–0.5 ml. If the fluid is given too fast, the rabbit will choke or the liquid may escape out of the mouth.

Procedure: To place a naso-oesophageal feeding tube

Rabbits always breathe through their noses, so this procedure is not recommended for rabbits showing signs of respiratory distress.

1. Action: Select a 5–8 F (French gauge) feeding tube.

Rationale: The size depends on the size of the rabbit.

2. Action: Lay the tube along the outside of the rabbit’s body, from the external nares to the caudal end of the sternum. Mark the point of the external nares with a tape or ballpoint pen.

Rationale: As the tube is passed through the nasal cavity and down the oesophagus, the pen or tape mark will reach the opening to the nasal cavity and indicates that the end of the tube has reached the distal oesophagus, close to the entrance to the stomach.

3. Action: Restrain the rabbit in sternal recumbency and wrap in a towel as previously described.

Rationale: In this position the body is restrained but there is access to the head.

4. Action: Apply local anaesthetic spray to one of the rabbit’s nostrils. Wait for 3–5 minutes.

Rationale: This desensitizes the opening to the nasal cavity and facilitates tube placement.

5. Action: Apply lidocaine gel to the end of the tube.

Rationale: This lubricates the passage of the tube so that it can be inserted without resistance.

6. Action: Raise the rabbit’s head and place the tip of the tube into the selected nostril at the ventral meatus. Gently advance the tube medially and ventrally. Return the head to a normal position as the pharynx is approached. Continue until the mark on the tube lies at the entrance to the nasal cavity.

Rationale: This ensures that the tube passes down into the distal oesophagus.

7. Action: Take a radiograph of the lateral thorax and abdomen.

Rationale: It is important to check that the tube is in the oesophagus and not in the trachea. Introducing a small volume of saline down the tube is a simple means of monitoring, but rabbits do not always cough when this is done. The use of a lateral radiograph is a more reliable method. The rabbit will be conscious and must be restrained – make sure that correct radiological protection measures are carried out.

8. Action: Pass the external part of the tube over the bridge of the nose and between the ears. Fix in place using superglue, tape or sutures at the external nares and at the base of one ear.

Rationale: It is important that the tube is not dislodged by patient interference.

9. Action: If necessary, use a Buster collar.

N.B.: This technique can be used to administer liquid oral medication or for feeding hospitalized rabbits.

N.B.: If repeated injections are to be given, use an intravenous or a butterfly catheter held firmly in place with superglue or tape. If collecting a blood sample, use the saphenous, the cephalic or the jugular veins. The maximum volume that can be collected at one time is 2.5 ml.

Procedure: Intraperitoneal injection

1. Action: Place the rabbit in sternal recumbency on an examination table with a non-slip surface.

Rationale: If the rabbit feels secure it will be less likely to struggle and injure itself.

2. Action: Grasp the scruff with one hand and the hind legs with the other hand.

Rationale: The rabbit must be held firmly to prevent it struggling during the procedure.

3. Action: Pick the rabbit up and hold it in dorsal recumbency with its spine against your chest (Fig. 13.5).

Figure 13.5 Restraining a rabbit for an intraperitoneal injection.

Rationale: This position exposes the abdomen for injection, but care must be taken with dyspnoeic patients.

4. Action: The veterinary surgeon will introduce a short needle at a point midway between the xiphisternum and the pubis.

Rationale: This position should avoid accidental penetration of the bladder or stomach. Rabbit skin is thin and a short needle easily penetrates the abdominal wall.

5. Action: Draw back on the syringe and examine the contents.

Rationale: If blood, urine or gut contents appear, reposition the needle. If nothing appears in the hub of the needle, it is safe to proceed with the injection.

6. Action: If there is nothing in the syringe, gently inject the contents of the syringe.

Rationale: Up to 50 ml of fluid can be given by this route.

7. Action: When the procedure is complete, withdraw the needle.

N.B.: This technique can be used to collect samples of fluid from the peritoneal cavity and of urine from the bladder.

Procedure: To place an intraosseous catheter

1. Action: Select an appropriate site.

Rationale: In the rabbit the proximal femur and the proximal tibia provide ease of access and a medullary cavity from which fluid can be rapidly absorbed.

2. Action: Prepare the site aseptically.

Rationale: To prevent the introduction of infection.

3. Action: Infiltrate the area with local anaesthetic.

Rationale: To desensitize the tissues. The rabbit may be under a general anaesthetic but this depends on the nature and condition of the individual patient.

4. Action: Select a spinal needle or plain needle of an appropriate size and insert it into the bone.

Rationale: The needle must be of a size that will enter the medullary cavity – use a radiograph of the leg or previous experience to assess the size.

5. Action: Flush the needle with heparinized saline.

Rationale: The needle may become blocked with tissue fragments. Heparinized saline will ensure that it is patent.

6. Action: Fix the needle in place with tissue glue or by suturing.

Rationale: It is important that the needle does not become dislodged.

7. Action: Attach a short length of tubing and a syringe or attach a fluid giving set to the needle.

Rationale: This procedure may be used to give a bolus of fluid or a slow infusion. Absorption from this site is as rapid as the intravenous route.

8. Action: If the needle is to be left in situ, bandage the area. You may need to use a Buster collar.

Rationale: To prevent the risk of infection, to reduce limb mobility and to prevent patient interference. A Buster collar will also prevent interference but intraosseous catheters are usually well tolerated.

9. Action: When giving further fluid or drugs through the needle maintain an aseptic technique.

Rationale: To prevent the introduction of infection.

10. Action: Flush with heparinized saline before each use.

Rationale: To flush out any blood clots.

11. Action: Keep the needle patent by flushing with heparinized saline at least three times daily, even if it is not being used.

Rationale: To maintain patency.

N.B.: This route is useful for small animals whose veins are often fragile and easily damaged by needles and catheters. If the needle is dislodged, haemorrhage from the site is unlikely to occur.

GENERAL ANAESTHESIA

For general considerations, see Table 13.2.

Table 13.2

Points to be considered during anaesthesia of the rabbit

Action	Rationale
1. There is no need for pre-operative starvation of rabbits	1. Rabbits are unable to vomit. Starvation may cause a fatal hypoglycaemia, especially in smaller individuals. The stomach is never completely empty as rabbits exhibit coprophagia
2. Avoid dehydration by giving fluids intravenously, subcutaneously, intraperitoneally or intraosseously	2. Rabbits undergoing a routine procedure can be given a bolus of fluid
3. Keep the patient warm at all times using a heat pad or by wrapping in ’bubble wrap’ but check regularly for signs of hyperthermia	3. Hypothermia may be a problem in small animals, particularly during anaesthesia and post-operatively, as they have a large surface area in relation to their body weight. Anaesthetics depress temperature regulation and may cause vasodilation. If viscera are exposed during surgery, heat loss will be increased
4. Apply an ophthalmic lubricant to protect the eyes	4. Rabbits have bulging eyes, which are prone to drying out during anaesthesia. If ketamine is used in any anaesthetic combination, the eyes will remain central and fixed
5. Make sure that the tongue is pulled forward if the patient is not intubated	5. A rabbit’s tongue is large and may obstruct the airway

Procedure: Induction of anaesthesia

1. Action: Weigh the rabbit.

Rationale: To calculate the correct dose of anaesthetic. It is important not to overdose the patient.

2. Action: During the induction process the rabbit must be handled gently and calmly.

Rationale: This process easily distresses a rabbit and it may contribute to cardiac or respiratory arrest or gut stasis post-surgery.

3. Action: If using an injectable agent, e.g. fentanyl/fluanisone or ketamine/medetomidine, give by the appropriate route; restrain the patient as described previously (Table 13.3).

Table 13.3

Anaesthetic agents used in small rodents and rabbits

Drug	Species, dose rate and route of administration				Duration of anaesthesia
	Mouse	Rat	Guinea pig	Rabbit	Duration of anaesthesia
Fentanyl/fluanisone (Hypnorm)	0.2–0.5 ml IM 0.3–0.6 mg/ml IP	As mouse	–	0.2–0.4 ml	Sedation only 30–45 min
Fentanyl/fluanisone (Hypnorm)/diazepam	0.4 ml/kg 5 mg/kg	0.3 ml/kg 2.5 mg/kg	1 ml/kg IM 2.5 ml/kg	0.3 ml/kg IM 2 mg/kg IP	45–60 min
Fentanyl/fluanisone (Hypnorm)/midazolam*	10 ml/kg*	2.7 ml/kg*	8 ml/kg*	0.3 ml/kg IM 0.5–1 ml/kg IV	45–60 min
Ketamine/medetomidine	200 mg/kg 0.5 mg/kg	90 mg/kg 0.5 mg/kg	40 mg/kg 0.5 mg/kg	35 mg/kg 0.5 mg/kg	20–30 min
Propofol	26 mg/kg IV	10 mg/kg IV	–	10 mg/kg IV	5 min
Atipamezole	1 mg/kg IM, IP, SC, IV to reverse any combination using medetomidine

IM, intramuscular; IP, intraperitoneal; IV, intravenous; SC, subcutaneous.

^*One part fentanyl/fluanisone (Hypnorm) to one part midazolam (5 mg/ml) to two parts water.

Source: Hotston-Moore (1999).

Rationale: Injectable agents provide a rapid and stress-free induction. Use small syringes for more accurate dosing.

4. Action: Supplement with oxygen by mask or by intubating the patient.

Rationale: This should be done even when using injectable agents.

5. Action: If using inhalation anaesthesia, e.g. isoflurane, induce using a mask or an induction chamber.

Rationale: Using a mask is easier if the rabbit has been given a premedicant. An induction chamber of a suitable size for the patient may take several minutes to fill. Induction by either of these methods is not recommended as the rabbit may hold its breath or may struggle violently, injuring its back. The most commonly used anaesthetic, isoflurane, is irritant to mucous membranes.

6. Action: Give 100% oxygen for 1–2 minutes before attempting to intubate the rabbit.

Rationale: To increase the oxygen concentration in the anaesthetic mixture. Intubation is more difficult than in the dog and the cat and may take longer as the glottis and larynx are not visible.

7. Action: Intubate the rabbit by placing it in sternal or dorsal recumbency with the head and neck extended. Use a laryngoscope to illuminate the area and an introducer, such as that found inside a cat urinary catheter, to stiffen the endotracheal tube. Slide the tube over the introducer into the trachea and remove the introducer.

Rationale: The glottis of the rabbit is small and obscured by the tongue. A fatal laryngospasm may occur if care is not taken.

8. Action: Alternatively, intubation may be performed ‘blind’. Estimate the position of the larynx externally and advance the endotracheal tube until it lies in the correct position. Check for correct positioning.

Rationale: The larynx may be palpated externally. Listen for respiratory sounds through the tube to check positioning. A transparent tube may show evidence of condensation from the moisture in the exhaled breath.

9. Action: Attach the endotracheal tube to the anaesthetic circuit.

Rationale: Circuit must be appropriate to the species, e.g. Ayer’s or Jackson Rees modified T-piece.

10. Action: Take appropriate steps to keep the rabbit warm at all times.

Rationale: Heat loss can be reduced by wrapping in ’bubble wrap’ or a ‘space blanket’ and by use of a heat pad.

11. Action: If possible raise the chest above the abdominal cavity.

Rationale: The thoracic cavity is small and can be compressed by the abdominal contents.

Procedure: Maintenance and monitoring of anaesthesia

1. Action: Make sure that you are familiar with the reactions of the rabbit under general anaesthesia.

Rationale: Rabbits are not as relaxed as dogs and cats.

2. Action: Pay particular attention to the rate and depth of respiration.

Rationale: This is the most reliable method of monitoring the depth of anaesthesia. Laboured breathing and pauses between breaths indicate deep anaesthesia.

3. Action: Monitor the tension of the jaw.

4. Action: Pinch the ear.

Rationale: Absence of a head shake indicates an acceptable level of surgical anaesthesia.

5. Action: Assess the pedal reflex.

Rationale: This reflex remains for longer than in the dog and cat and is only lost under deep anaesthesia.

6. Action: The corneal and palpebral reflexes can also be used to assess depth of anaesthesia.

Rationale: These are similar to those in the dog and cat.

Procedure: Post-operative care

1. Action: The rabbit must be monitored until it is completely conscious and behaving normally.

Rationale: Avoid too much direct attention, e.g. talking to the rabbit, as this will increase the levels of stress. Observe from a discreet distance.

2. Action: Place the rabbit in a cage in a room which is warm, quiet and dimly lit.

Rationale: Bright lights and noise will distress the rabbit during recovery.

3. Action: Ensure that the rabbit is kept warm using a heatpad or Vetbed, or blankets or towels placed under and over the body. Avoid the use of shavings or hay.

Rationale: Hypothermia can be fatal or will prolong the recovery period. Loose bedding such as shavings may clog the mouth and nose.

4. Action: Monitor the core temperature until completely conscious.

Rationale: Use a rectal thermometer but try to avoid excessive manipulation of the recovering rabbit.

5. Action: If necessary be prepared to give oxygen.

Rationale: This will increase the rate of recovery.

6. Action: If the rabbit shows signs of pain, e.g. tooth grinding, grunting, lack of appetite, or if the condition warrants it, provide analgesia.

Rationale: Any procedure that would cause pain in any other species should be considered to cause pain in the rabbit and would warrant the use of analgesics. Correct use of analgesics, e.g. carprofen or buprenorphine, will do no harm.

7. Action: If the rabbit does not eat or drink soon after recovery, consider providing fluid therapy – either intravenously or intraperitoneally; this should include glucose.

Rationale: Lack of fluid may rapidly cause serious dehydration. Lack of food may lead to a fatal hypoglycaemia. Both will compromise recovery.

8. Action: Monitor urine and faeces output.

Rationale: General anaesthesia and surgery may impair both kidney and intestinal function. Overhandling of the intestine may cause paralytic ileus, which is indicated by a lack of faeces.

SMALL RODENTS

For biological data, see Table 13.1.

HANDLING AND RESTRAINT

It is the natural response of a frightened rodent to bite. This can be avoided by knowing how to handle each species correctly, but if you are bitten:

• Replace the rodent in its cage with your finger still in its mouth. As the rodent feels its feet on a firm surface it should let go!

• Do not attempt to pull your finger from the rodent’s mouth, as the injury will be made worse by the backward-pointing curved teeth.

• Do not shake the rodent off your finger, as this will cause serious injury to the rodent.

• Wash the bite thoroughly under running water, apply antiseptic ointment and cover for as long as you are working with the animals.

• Consult your doctor if it becomes excessively painful or swollen.

• Keep your tetanus vaccination up to date.

THE CHINCHILLA – CHINCHILLA LANIGERA

Procedure: To restrain a chinchilla

1. Action: If the chinchilla is tame, pick it up by placing one hand around its shoulders.

Rationale: Chinchillas are relatively easy to handle; most are not aggressive and rarely bite. Be aware of the pressure you are putting on the chest as this can restrict normal breathing.

2. Action: Avoid grasping hold of the fur.

Rationale: Rough handling can cause patches of fur to come away in your hand – a condition known as ‘fur slip’. In the wild this mechanism enables the chinchilla to escape from predators. New fur may take several months to grow back and may be of a different shade.

3. Action: Once removed from the cage, most chinchillas will sit quietly on your forearm gently restrained by the base of the tail.

Rationale: If the animal feels supported and secure it will be unlikely to try to escape.

4. Action: More nervous or active animals can be lifted by the base of the tail, with your other hand supporting the body.

Rationale: Only lift by the base of the tail as further down may injure the tail. Do not leave the animal unsupported for any longer than is necessary.

5. Action: To restrain for any clinical procedure, hold the base of the tail with one hand and place the other around the shoulder and chest.

Rationale: This can be used to hold the animal firmly for procedures such as injection and examination.

Procedure: To sex a chinchilla

1. Action: Grasp the base of the tail with one hand and support the body around the shoulders.

Rationale: If the animal feels supported and secure it will be unlikely to try to escape.

2. Action: Hold the chinchilla in dorsal recumbency, moving the tail to expose the genital area.

Rationale: This can be done single-handedly unless the chinchilla struggles.

3. Action: Examine the genital area and measure the anogenital distance.

Rationale: This is the distance between the anus and the opening of the vulva (female) or the penis (male) and is longer in the male than in the female (Fig. 13.6).

Figure 13.6 General method of sexing rodents: A, hamsters; B, mice.

The female chinchilla has a large cone-shaped clitoris, which may be mistaken for the penis of the male. Adult male chinchillas have a pair of large testes which are very obvious during the breeding season of November–March.