PHYSICAL EXAMINATION AND DIAGNOSTICS

A thorough physical examination can only be achieved on an anaesthetised echidna (see Chapter 9). Mentation, gait, posture, respiration and pelage can be assessed in the conscious echidna, and beak and body condition can be partially assessed.

Additional information on diagnostics is available in Middleton (2008), Holz (2015), Vogelnest and Allan (2015) and Vaasjo et al. (2024). Non-invasive techniques have been validated for faecal glucocorticoids (Russell et al. 2022), faecal progesterone (Dutton-Regester et al. 2023a) and DNA sexing from fur, quills and faeces (Perry et al. 2019; Braga et al. 2022; Hulse et al. 2024).

4.1 Body condition and bodyweight

A detailed visual body condition scoring guide for echid­nas has been developed at Taronga Conservation Society Australia Zoo and will be published separately. Body condition can be subjectively assessed based on the fol­lowing parameters (Fig. 29.2):

• circumference shape (viewed from above) - ranges from distinct hourglass shape indicating under-condi­tion to oval to round indicating over-condition

• dorsal profile (viewed in the dorsal plane either crani- ocaudally or caudocranially) - ranges from a pointed to narrow dome indicating under-condition, to a wide dome indicating over-condition

• antebrachial muscle mass

• degree of abdominal concavity and epipubic and pelvic bone protrusion when in dorsal recumbency - concave and prominent bone protrusion indicating under­condition and flat or convex with minimal bone pro­trusion indicating over-condition

• lateral skin fold thickness assessed under anaesthesia - a wide, non-compressible fold indicates over-condition, a narrow fold indicates under-condition.

Echidna body condition in both free-ranging and managed care varies significantly throughout the year, with under- and over-condition representing a normal and expected range. However, in rescued or sick echid­nas, body condition may be an important clinical consideration.

Adult echidnas weigh between 2 and 7 kg. Seasonal bodyweight variation in free-ranging echidnas differs significantly depending on geographical region. Although there is little variation when food availability is constant (Johnston et al. 2007), there is significant varia­tion (up to 30%) in free-ranging echidnas in Tas. and on Kangaroo Is. Males are at their lowest weight towards the end of the breeding season (August), because of increased

Fig. 29.2. Subjective assessment of body condition in an anaesthetised short-beaked echidna (Tachyglossus aculeatus) in good body condition. (a) Circumference shape: slight hourglass shape; (b) dorsal profile assessing dorsal dome shape: rounded dome; (c) assessment of lateral skin fold: moderately wide. Photos: Michelle Shaw

trailing activity and decreased feeding (Rismiller and McKelvey 2003; Morrow et al. 2016). This has also been observed in zoo-housed breeding males during the breeding season.

Female Tasmanian echidnas undergo large changes (up to 22%) in bodyweight throughout the year (Nicol and Morrow 2012), with gestation, incubation and early lactation coinciding with lowest weights. These females are usually burrow-bound at these times.

Echidnas in managed care may have weight variations up to 2 kg. Adult weights are higher in autumn/early winter and lower in spring/early summer. This may be related to preparation for torpor/hibernation followed by an increased metabolic rate during the warmer months.

4.1 Evaluation of the gastrointestinal tract

The tongue should be examined closely for evidence of ulceration, roughening or plaques and saliva production assessed (excessive or reduced). The tongue and oral cavity must be evaluated cytologically in inappetent or dysphagic echidnas.

Gastric fluid aspiration for pH, cytology and microbi­ology is relatively easy to perform and is recommended for any sick echidna where the cause of illness is not apparent (Fig. 29.3). The echidna is lightly anaesthetised and positioned in ventral recumbency supported by towels and a handler. The tongue is extracted from the oral cavity using a cotton tip and pulled gently forward without excessive traction. The beak should be angled around 100° to the body to minimise risk of glottal intu­bation. A 10-12Fr red rubber feeding tube is passed over the tongue and will usually halt as it reaches the pharynx. With gentle prodding and assistance of the echidna’s swallowing reflex the tube will pass into the oesophagus to the stomach. It is imperative to pre-measure the

Fig. 29.3. Correct position for gastric aspiration; note the angle of the beak to the body.

distance between the tip of the beak and halfway down the body to confirm gastric placement. If resistance is continuously encountered do not continue. The tube may be passed more easily with the neck extended but this increases the risk of accidental intubation - this can be avoided with a larger diameter tube but increases the risk of airway obstruction. Alternatively the tube may be passed with the animal in dorsal recumbency. If fluid is not immediately aspirated, a small amount of saline can be instilled.

Barium contrast radiography is useful if gastric impac­tion or obstruction is suspected. Approximately 10-20 mL barium sulfate, or iohexal, is mixed with food and fed to the echidna. Alternatively 5-10 mL is administered by gavage.

Endoscopic visualisation of the upper GIT is possible with a small diameter (<4 mm) flexible endoscope. Larger endoscopes are more difficult to pass and may obstruct the larynx.

Faecal appearance is variable and depends on the diet and access to soil and is graded as follows: 1 - extremely dry, 2 - firm, 3 - soft with shape, 4 - soft without shape and 5 - liquid (Stannard et al. 2017). Free-ranging echid­nas typically pass solid, smooth and cylindrical faeces containing exoskeletons of prey items and substantial quantities of dirt (grade 2), whereas echidnas in managed care on gruel diets without access to soil to ingest will pass grade 3-4 faeces. Grade 5 faeces, melaena or haema- tochezia should be investigated without delay. Free-rang­ing echidna GIT transit time is 48 h compared to 24 h in echidnas in managed care (Higgins et al. 2018; Dutton- Regester et al. 2023b).

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