SHORT-BEAKED ECHIDNA
2.1 Capture and physical restraint
Short-beaked echidnas (Tachyglossus aculeatus) are very strong, have sharp quills (the tips of which can cause considerable irritation to human skin) and curl into a tight ball when handled.
They dig in and grasp firmly to any substrate when approached and can wedge themselves securely beneath or within structures. Extraction with protected hands (thick towel or protective gloves) or careful use of a shovel may be necessary if the echidna has dug into soil. Extraction from soft soil can sometimes be accomplished by positioning oneself behind the echidna, then placing a hand on either side of the ventroflexed head and shoulders and rolling the animal towards you, quickly grasping a hindlimb to suspend it as described below (Middleton 2008; NHMRC 2014; Holz 2015). In some situations, chemical restraint via IM injection may be required to facilitate extraction and capture (see section 2.2).Once extracted or on smooth, firm substrates, slide gloved or ungloved hands beneath the echidna from each side. The body will curl around the hands with the head held tight against the ventrum. The echidna can then be lifted and held securely against the protected body of the handler. A hindfoot may also be grasped by the elongated claws or tarsus and the echidna suspended briefly by the hindlimb. As the echidna uncurls, slide the other hand beneath the body, lifting it off the ground while supporting it. Habituated zoo-housed echidnas can often be picked up by simply placing the hands under either side of the body. Little can be accomplished in terms of examination or sample collection from a conscious echidna unless it is habituated to handling. Once captured the echidna can be placed in a suitable receptacle (e.g. plastic garbage bin, large plastic storage container) for transport or shortterm holding or it can be injected.
Echidnas will rapidly destroy and escape from a cardboard box. For examination and other procedures chemical restraint will be required (Middleton 2008; NHMRC 2014; Holz 2015).Echidnas have a relatively low body temperature (32°C) and their body temperature can vary with ambient temperature. Their thermoneutral range is 20-30°C. Above around 28°C heat loss is minimal and hyperthermia will develop. Capture and handling of echidnas should be avoided at high ambient temperatures and if unavoidable, means for cooling must be available (Middleton 2008).
2.2 Chemical restraint
For anything other than minor procedures, such as injections or transport, chemical restraint is required. Preanaesthetic fasting requirements are provided in Table 9.1. Injectable agents have been used for sedation, induction before maintenance with gaseous agents, brief examination, sample collection, minor treatments or when difficult to extract from a surface or space (see Appendix 3). IM injections can be given in the hindlimbs or epaxial muscles (useful in unrestrained echidnas that cannot be extracted for physical restraint).
Anaesthetic induction is achieved using injectable or gaseous agents. Injectable agents administered IM into the epaxial muscles are preferable as it requires minimal restraint and is less stressful for the animal. For gaseous induction, a tube-shaped mask (improvised from syringe barrels or plastic bottles) is placed over the beak. Most echidnas will ventroflex the neck after mask positioning and remain reasonably immobile until induced. Alternatively, an induction chamber can be used, which avoids the need to physically restrain the patient. The chamber must be strongly constructed to withstand the echidna’s physical strength (Middleton 2008; Holz 2015).
Options for injectable chemical restraint agents are provided in Appendix 3. Isoflurane or sevoflurane in oxygen is generally used for induction (if an injectable agent is not used), supplementation and maintenance of anaesthesia.
Induce by gradually increasing the isoflurane concentration to 5% using 1.5 L/min oxygen. Echidnas can generally be maintained on 1.5-2%. Maintenance is via a mask as echidnas are very difficult to intubate because of their narrow oral cavity, small gape and the presence of a keratinous pad on the dorsal surface of the base of the tongue making it difficult to visualise the larynx (Holz 2015). If required, to maintain an airway, an appropriately sized endotracheal tube may be inserted to just beyond the base of the tongue until air can be detected moving through the tube. The tube cuff can be inflated to create a seal. Visualisation of the glottis and larynx and intubation with the aid of a small rigid endoscope has been described (Reynolds and Sommerland 1996).Standard small animal monitoring equipment can be used; however, attachment of oximetry sensors may be difficult. Regular visual observation of respiration and monitoring of heart rate and rhythm via stethoscope are more useful. Complications in healthy echidnas are rare. Echidnas are tolerant of increased CO2 concentrations and respond by increasing tidal volume rather than respiratory rate. Thus, respiratory rate may not be a reliable monitoring parameter during anaesthesia (Rissman 2000). Periods of apnoea are also common and may be accompanied by bradycardia. This is usually transient and recovery is spontaneous; however, in some cases stimulation and/or reduction in isoflurane concentration is required. Hypo- or hyperthermia may occur and mechanisms for cooling or warming should be available if anaesthesia in extreme temperatures is unavoidable. Anaesthesia in sick or traumatised individuals, especially in those with beak injuries, can be complicated. Damaged soft tissue, fractures, blood and saliva may block the airway. Mask induction may be difficult. Injectable induction may be preferable; however, once the animal is anaesthetised, attempts must be made to keep the airway clear, by manually removing obstructions or with the passage of an appropriately sized endotracheal tube as described above. Gently inserting an 18G catheter into a nostril may allow adequate ventilation during anaesthesia, provided the patency of its lumen is maintained (Middleton 2008).
3.