MANAGEMENT AND TREATMENT OF SICK OR INJURED KOALAS

Pharmacology and treatment of chlamydiosis are covered in Chapters 11 and 35 respectively. Specific drugs and doses used in koalas are provided in Appendix 4. Readers should refer to Blanshard and Bodley (2008) for further information on therapeutics not covered here.

3.1 Intensive care

Provision of a quiet, semi-dark, suitably warm environ­ment with minimal disturbance will improve the welfare and treatment outcomes of koalas under intensive care. The size and characteristics of enclosures should be appropriate to the state of patient: severely ill koalas or

Fig. 33.2. Short extension tubing attached to an indwelling IV line. A blood sample is being collected while the koala (Phascolarctos cinereus) remains asleep. The line is flushed with heparinised saline after each use. Photo: Larry Vogelnest

those with severe trauma should be in small, tempera­ture-controlled enclosures with padding and suitable bedding; as their function and mobility are restored, patients can be provided with upright perches and then usual koala enclosure furniture as behaviour and mobil­ity return to normal. Minimising disturbance and limit­ing procedures to only those necessary for appropriate monitoring and therapy are important. Koalas must be given the opportunity to sleep for long periods to mini­mise energy expenditure and stress. Establishing indwell­ing IV lines with short extension tubing (Fig. 33.2), allowing easy connection and removal of drip lines, blood collection and administration of IV antibiotics and anal­gesics will minimise the need to restrain and/or unneces­sarily disturb the patient.

Normalising oxygenation and body temperature, haemodynamic stabilisation and providing nutritional support are important.

Table 33.2. Peritoneal fluid parameters in normal, sick or injured koalas (Phascolarctos cinereus)

500 CurrentTherapyin MedicineofAustraIian Mammals

33 - Koala

Table 33.3. Suggested intensive care protocols for koalas (Phascolarctos cinereus) (see Appendix 4 for drug doses)

502 CurrentTherapyin MedicineofAustraIian Mammals

Table 33.3. (continued)

504 CurrentTherapyin MedicineofAustraIian Mammals

*May not be required following a fentanyl CRI reduced to 0.5-1 μg∕kg per hr or when using a fentanyl patch.

**Paste formulas as described in Blanshard and Bodley (2008) or Crittacare Koala (Vetafarm, Wagga Wagga, NSW, Australia)

susceptible to trauma and homeostatic disturbance during serious illness, caused by, for example, dysbiosis through antibiotic use, inappropriate diet and traumatic injury (see section 4.5.1).

For juvenile koalas treatment should be instituted promptly, as they can deteriorate rapidly.

3.1.1 Fluid therapy

Fluid rate and duration should be objective and adaptive, that is, for example, aimed at improving pulse quality or correcting dehydration. Fluid rates higher than mainte­nance (i.e. >3 mL/kg per hr) should be discontinued when the objective measure has been achieved.

In small joeys (<1 kg), in which venous access is diffi­cult, the IO route is very effective and provides rapid access to the systemic circulation. IO lines are easy to establish; access is achieved by placing a small hypoder­mic needle (26-23G, 19-mm) into the medullary cavity of the tibia via the tibial crest. This can then be con­nected to a low-volume extension set and syringe pump for fluid and drug administration. In adults, fluid rates and types should be based on the condition being treated and response to therapy, including regular monitoring of TPP and PCV. Any drugs or fluids able to be used IV can be used IO, although dilution of irritant drugs is recom­mended. The IO route can also be used in adult koalas, when venous access is difficult, but may require special­ised IO catheters because of the increased density of bone.

Head trauma

Intracranial injury should be presumed in all cases where obvious external head trauma is evident. Some clinicians preferentially use hypertonic saline (HTS) (7% and 3% sodium chloride) over diuretics (e.g. mannitol) for head trauma in koalas, based on observable improved outcomes and in line with current recommendations in human medicine (Catrambone et al. 2008; Elliott et al. 2007; Exo et al. 2009; Hinson et al. 2013; Huang et al. 2006; Mar­gulies and Hicks 2009). The administration of HTS results in movement of fluid from the cerebral interstitial and/or intracellular spaces into the intravascular compartment, via an increase in plasma colloidal osmotic pressure (Huang et al. 2006), increasing circulatory volume with reduced risk of increased intracranial pressure.

Severe haemorrhage and hypoproteinaemia

Koalas with traumatic injuries often suffer internal and external haemorrhage. This may be profuse, requiring large volumes of crystalloid fluids, tailored boluses of col­loidal fluids or blood transfusions. Whole blood or packed red cells (PRC) can be administered at 2 mL/kg or 1 mL/kg respectively for every 1% increase in PCV desired. Plasma transfusions at 30-40 mL/kg are most commonly required in koalas suffering protein loss from GI injury or disease or extensive burns. Cross-matching is not required and koalas appear to tolerate multiple transfusions of blood and plasma, from multiple donors, without any adverse effects. If whole blood is not availa­ble, PRC and frozen plasma can be combined as a suitable alternative. The collection and storage of blood and plasma in koalas is as for domestic species.

3.1.2 Antibiotics

Antibiotics should be used judiciously and conservatively in koalas because of the risk of fatal GI dysbiosis (see sec­tion 4.1.1). Strict aseptic technique for surgical procedures and wound management (e.g. surgical exploration and debridement of penetrating wounds [e.g. dog attack wounds], removal of foreign debris, contaminants and devitalised tissue) is often more beneficial than the use of systemic antibiotics. Copious irrigation of contaminated wounds, the abdominal cavity (in peritonitis) and surgi­cal sites with saline may similarly reduce the requirement for antibiotics. Topical antibiotic or antiseptic prepara­tions are often sufficient to control local infections, obvi­ating the need for systemic antibiotics. Water soluble pluronic gel (concentrations up to 30%) mixed with gen- tamycin (or other suitable antimicrobial) and deposited into infected wounds q 3-4 d provides good local antimi­crobial treatment.

When used, indications should be clear and choice ideally based on culture and susceptibility testing. Indica­tions for antibiotic use may include a combination of neutropenia or leucopenia; pneumonia; sudden onset of hypoglycaemia; septic peritonitis; hypothermia; and heavily contaminated deep puncture wounds that cannot be managed exclusively through debridement and irriga­tion. In some cases, aggressive IV antimicrobial therapy is indicated, particularly in juvenile koalas and cases of acute sepsis and bacteraemia. Severe infections should be treated with appropriate IV antibiotics rather than high doses or long courses of IM, SC or PO antibiotics. Appro­priate IV antibiotics in these cases may include ceftazi­dime, enrofloxacin, gentamicin or ciprofloxacin (see Chapter 11 and Appendix 4).

3.1.3 Analgesia

Signs of pain in koalas include ear flicking, tachypnoea, reduced mentation, sitting hunched on the ground reluc­tant to move, bruxism, cool, sweaty foot pads, grunting two-phase respiration and vocalising. Opioids provide the most effective analgesia for patients with moderate or severe pain and should be used to manage pain associated with fractures, visceral injury or severe soft tissue trauma. Duration of opioid use should be kept to a minimum (<96 hr) and a gastric prokinetic such as cisapride admin­istered concurrently (see Table 33.3). Transdermal fenta­nyl patches may provide some analgesia for 3 d but take at least 12 hr from application to take effect (Tokonami et al. 2021). Tramadol administered at 4 mg/kg SC is predicted to have some analgesic activity (Kimble et al. 2021) and has been used in koalas with moderate to severe pain (cases of long bone fractures and soft tissue injury) with­out apparent analgesic effect. NSAIDs can be used con­currently but are inadequate for moderate to severe pain and there are mixed perceptions regarding efficacy (de Kauwe et al. 2014). Pharmacokinetic studies on meloxi- cam in koalas demonstrate poor oral bioavailability, rapid hepatic metabolism and subsequent clearance following IV administration, suggesting its efficacy in managing pain at standard doses is likely to be very poor (Kimble et al. 2013). Alternative NSAIDs such as carprofen, firo- coxib and tolfenamic acid appear anecdotally to be more effective, although pharmacokinetic data is limited. In- vitro studies of caprofen show a short half-life and rapid clearance in the koala (Lillo 2020). Paracetamol, with or without codeine, is often used to provide mild analgesia and can be used in conjunction with other analgesics. Pharmacokinetics of oral and SC paracetamol suggest good oral bioavailability (Govendir et al. 2024). IV par­acetamol has been trialled in several koalas with limited apparent benefit and severe phlebitis in one case. Sug­gested pain management protocols for common condi­tions are presented in Table 33.3.

3.1.4 Feeding and nutritional support

Critically ill koalas or those with GI disorders or receiv­ing opioids are frequently inappetent. Feeding regimens, leaf selection and supplement feeding require special consideration to avoid inducing or exacerbating GI dis­ease, while still maintaining nutritional intake. ‘Leaf drop’ in convalescing koalas may be observed as scatter­ings of individual leaves on the floor where a koala is sit­ting. This may be from oral candidiasis (see section 4.1.2) where affected koalas may be hungry, but reluctant to eat, often mouthing but not chewing leaf, or dropping leaf (leaf drop) from their mouth because of oral irrita­tion. This is also seen when koalas remove leaf from the stem to preferentially eat the fibrous stems (often observed in koalas with GI disease). Inappetent koalas, or those with severe GI stasis, should not be administered paste formulas (including Crittacare Koala) because this can lead to bloating, exacerbation of GI stasis and pro­gression of caeco-colic dysbiosis/typhlocolitis syndrome (CDTS) (see section 4.1.1). Recommended nutritional supplementation is outlined in Table 33.4.

Leaf selection and provision of dirt

Koalas should be provided a variety of good-quality, fresh browse daily, even if they do not appear to be eating. Injured and debilitated koalas often have fluctuations in appetite and leaf preference and require close monitoring to ensure their intake of leaf is sufficient to meet their nutritional requirements. Koalas suffering from facial frac­tures or oral injury should be fed the softest leaf tip availa­ble. Koalas with GI disturbances may reject soft leaf tip but readily eat mature leaf, and may preferentially browse on non-eucalypt species, such as Lophostemon spp., Melaleuca (Callistemon) spp. and Casuarina spp. These should be made available to inappetent convalescing koalas. Hand­feeding may stimulate self-feeding and should be attempted at least twice daily for inappetent koalas. Exposing koalas to sunshine or placing them outdoors for short periods with fresh leaf may also stimulate eating.

Table 33.4. Nutritional supplementation for koalas (Phascolarctos cinereus) under intensive care

¹Paste formulas as described in Blanshard and Bodley (2008) or Crittacare Koala (Vetafarm, Wagga Wagga, NSW, Australia) *Yes if still eating some leaf.

#Not required if feeding paste combined with blended leaf.

Soil or termite mound should be offered to all koalas.

Lophostemon spp. (brush box and swamp box) and other non-eucalypt species are often preferred by northern koalas with severe oxalate nephrosis and they may refuse even the softest eucalypt new growth. This may reflect dietary ‘self-medication’ or lower levels of oxalate or oxa­late precursors in these species (J Loaderpers. comm.).

Immature and semi-mature eucalyptus leaf has been shown to contain high levels of ascorbate (Immelman et al. 2020). In humans, high dietary ascorbate is known to be a precursor for oxalate formation and can lead to large increases in the production of oxalate within the body (Laker 1983). The significance of high dietary ascor­bate in koalas is currently unknown but the complex leaf preferences koalas display during periods of illness war­rants further investigation. It is likely that the avoidance of immature stages and sometimes any eucalyptus leaf displayed by unwell koalas is linked with their complex olfactory and metabolic systems.

Free-ranging koalas have been observed eating soil and termite mound (Melzer et al. 2014). This may be for minerals or digestive enzymes excreted by termites involved in lignocellulose and nitrogen metabolism (Wong et al. 2014). Koalas with GI disturbances often ingest soil or termite mound dirt when it is offered and this may be another form of ‘self-medication’. Shallow dishes of dry top-soil or termite mound dirt should be available to koalas undergoing intensive care and reha­bilitation and replenished as required.

3.2 Transfaunation

Caecal content from recently dead koalas can be used to transfaunate sick koalas. Caecal contents should be col­lected from recently dead koalas and stored refrigerated in air-tight containers. When stored in this manner it can be used up to 1 mo after collection (J Loader pers. comm.) though is best used within 14-21 d. For longer storage, the addition of 30% glycerol by weight of caecal contents after collection may improve survival of organ­isms when frozen (M Blyton pers. comm.). Ideally, donors should be Chlamydia-free, as there is a risk of transmission to the recipient. The minimum volume of caecal contents required to sufficiently recolonise the gut is unknown; however, successful transfaunation has been achieved using volumes in the order of up to 30-60 mL bid or tid. Smaller volumes and less frequent administration may also be efficacious and may be nec­essary when a ready supply of caecal content is not avail­able. The use of fresh faecal pellets from healthy koalas has been used as a substitute and either macerated in water and given orally, or made up in a paste formula supplement. However, the number of viable microbes and microbial composition is likely to be inferior to that of fresh caecal contents. The use of acid-resistant cap­sules to bypass stomach acid for transfaunation may improve colonisation success, but requires further investigation (Blyton et al. 2019). Improved appetite of koalas suffering dysbiosis should be apparent within 7-10 d if transfaunation has been successful.

3.3 Wound management

Wound management in koalas should be based on the same fundamental principles of wound care in other spe­cies. However, because of the need to avoid systemic anti­biotics in koalas whenever possible, thorough debridement and flushing of wounds, and use of appropriate topical antimicrobials is particularly important.

For wounds with significant skin deficit, where pri­mary or secondary intension healing is not possible or for non-healing wounds, skin flaps and grafts have been suc­cessfully used. Full-thickness large (6-8 mm) punch biopsies of skin from the koala’s abdomen can be trans­planted as grafts into the wound. Grafts should be pro­tected from injury with non-adherent dressings and soft bandaging for at least 14 d or until the tissue around the graft appears to granulate. Vacuum-assisted closure has also been used in koalas for the treatment of severe degloving injuries and post-infection wound breakdown (Saziye and Afksendiyos 2015).

4.