THERAPEUTICS
There are no published pharmacokinetic studies in echidnas and dose rates are usually based on those for cats and dogs. Drug dose rates and routes of administration are provided in Appendix 4.
Fluid therapy is covered in Chapter 30.Table 29.2. Normal and Clinicopathological findings in samples collected from short-beaked echidnas (Tachyglossus aculeatus)
| Sample | Normal findings and interpretation |
| Blood | Haematology and biochemistry reference intervals are presented in Appendix 1. Nucleated RBCs are detected in severe anaemia while reticulocytes are rarely seen.1 Haemoprotozoa are a common finding in healthy echidnas.2,3 RBC piroplasms, likely Theileria tachyglossi, are found in 88% of free-ranging echidnas and are an incidental finding.3 Intramonocytic protozoa are reported in 50% of echidnas in managed care and 56% in free-ranging echidnas, at intensities of 36-54%.3,4 Although no statistical association with clinical status, intensities >20% occurred in 5% of echidnas, all with chronic disease.3 Initially morphologically described as Haemoproteus tachyglossi, next-generation deep sequencings have identified Eimeria echidnae (Chapter 30).5 Intramonocytic coccidia are commonly seen in healthy echidnas (Tachyglossus aculeatus) (Plate 30.1).1,2 Metamyelocytes are reported in healthy echidnas and can be misidentified as 'atypical' monocytes.6 However, progenitor leucocytes are a negative prognostic indicator in sick echidnas. Hypoglycaemia is a common finding in echidnas with systemic infection and suspected sepsis. High BUN has been noted in echidnas fed a high-protein diet7 |
| Urine* | pH 5-6, USG 1.015-1.040 |
| Impression smears of tongue and oral swabs | Assessed using both Gram and modified Romanowsky stains. Normal oral flora consists of mixed bacteria and occasional non-budding yeasts. Neutrophils, RBCs, budding yeasts and pseudohyphae, +/- a heavy mixed bacterial population or predominantly gram-negative rods, are indicative of mycotic stomatitis (see section 7.1.1) |
| Gastric content | Gastric pH 8-8.5. Post-prandial decrease to pH 4.5 buffered by increased saliva. If saline is used to obtain an aspirate the pH will be around 7. Normal gastric cytology from echidnas on artificial diets includes a mixed bacterial population as well as non-budding yeasts. Lactobacillus is commonly cultured from gastric aspirates of healthy or sick echidnas at Taronga Zoo; however, it is not considered normal flora in free- ranging echidnas. Gastric aspirates from free-ranging echidnas contain gram-positive cocci and minimal to no yeasts. Epithelial cells, erythrocytes, neutrophils, mixed bacteria with primarily gram-negative and -positive rods and budding yeasts, with or without pseudohyphae, and a pH <7 are indicative of gastritis (see section 7.1.2) |
| Faeces | Faecal floatation and wet preparation results from healthy echidnas may contain low numbers of flagellates, low to high numbers of coccidia, low numbers of strongyle larvae or strongyle-type ova (Fig. 30.2) and occasional mites. Low numbers of non-budding yeasts are often detected in faeces. High numbers of budding yeasts are abnormal |
1Bolliger and Blackhouse 1960; 2Chapter 30; 3Hill etal. 2022; 4Ploeg etal. 2008; 5Slapeta etal. 2017; 6Whittington and Obendorf 2012; 7S Vitali pers. comm. *Urine samples are readily obtained via ultrasound-guided cystocentesis. Non-habituated echidnas can void a large volume of urine when handled.
6.1 Antibiotics
Antibiotics used in echidnas are included in Appendix 4. Any echidna treated with antibiotics should be monitored for secondary yeast infection.
Post-antibiotic transfauna- tion is recommended. There are conflicting anecdotal reports on the safety of injectable trimethoprim-sulfona- mide (TMS) preparations in echidnas. Adverse effects are commonly associated with sulfa-containing drugs in many species. Adverse haematological effects include haemolytic anaemia, agranulocytosis, leucopenia and thrombocytopenia (Lavergne and Trepanier 2007; Plumb 2015). Thrombocytopenia is immune-mediated and affects young, geriatric or previously sensitised patients. Hyperkalaemia and severe hypoglycaemia caused by increased serum insulin have been reported rarely (Pera- zella 2000; Strevel et al. 2006; Nunnari et al. 2010).Adverse effects were identified in all echidnas treated with parenteral TMS at Taronga Zoo (n = 5) for systemic coccidiosis. Abnormalities included clinical coagulopathy (5/5), thrombocytopenia (4/5), anaemia (2/5), neutropenia (2/5) and hypoglycaemia (2/5). The latter two abnormalities could have been related to sepsis because another echidna had the same changes before TMS treatment.
Oral TMS has been used on 13 occasions in 10 echidnas at Taronga Zoo. An adverse reaction was observed in one echidna that had been treated with two prior courses of injectable TMS. This echidna developed a severe anaemia, thrombocytopenia and injection site haematomas. The adverse drug reaction in this echidna was thought to be a result of sensitisation from prior treatment with TMS. Oral TMS currently remains the treatment of choice for clinical coccidiosis at Taronga Zoo (see Chapter 30; Appendix 4).
6.2 Antifungal drugs
Oral itraconazole, fluconazole, miconazole and amphotericin B are well tolerated in echidnas (see Appendix 4). Bioavailability of compounded itraconazole is variable in other species and when possible the commercial liquid preparation should be used (Sporonox, Janssen-Cilag, Macquarie Park, NSW) (V Barrs pers. comm.). Monitoring of hepatic enzymes during treatment with itraconazole is warranted.
Amphotericin B has negligible absorption from the GIT and is used as a topical enteric treatment. Miconazole gel (Daktarin Oral Gel, Janssen-Cilag, North Ryde, NSW) has been used to treat mycotic stomatitis. It can be administered directly PO or in a small amount of food.6.3 Antiprotozoal drugs
Clinical signs including inappetence, dehydration, lethargy, diarrhoea and neurological signs (abnormal head and tongue movements) have been observed following prophylactic toltrazuril administration if given for 3 d or more to clinically normal echidnas during a coccidiosis outbreak (see Appendix 4).
6.4 Anti-inflammatory drugs and analgesics
Prednisolone has been used in one echidna for suspected allergic blepharitis with no adverse effects. Multimodal analgesia using an opioid and NSAID is recommended for significant trauma, burns or post-surgical care. Tramadol, gabapentin (for chronic or neuropathic pain) and paracetamol have been used in echidnas with no adverse effects (see Appendix 4).
6.5 Gastrointestinal medications
The rumen-like environment of the echidna stomach facilitates successful oral transfaunation (Shaw 2022). Faecal transfaunation (see Chapter 14) from healthy zoo-housed donors has resulted in increased bodyweights in hand-reared echidnas with poor weight gain and is associated with resolution of diarrhoea in affected echidnas. Transfaunation is preferred over commercial probiotics. Faecal samples from healthy echidnas are used once daily for 3-5 d. Donor faeces should be free of nematode ova or larvae whereas evidence of cestodes is acceptable because of their indirect life cycle. Samples containing coccidial oocysts are suitable because the oocysts need to be sporulated in soil to be infectious. Faeces containing large numbers of flagellates should be avoided.
The choice of donor depends on whether the recipient is zoo-housed or a rehabilitation animal as the microbiome is diet dependent. Healthy zoo echidnas are suitable donors for other zoo echidnas on the same diet.
Rehabilitating echidnas should receive faeces from healthy free- ranging echidnas (e.g. wildlife trauma admissions). This is important prior to release to support microbiome transition, which in turn provides adaptive solutions for nutritional and detoxification challenges due to myrme- cophagy (Cheng et al. 2023). All echidnas should be offered supplementary termites, ants, earthworms, and fly pupae as the insect microbes may be important to maintain GIT health, as well as for enrichment (Shaw 2022). Crushed termite mound may also contain beneficial microbes.The GI motility modifier, cisapride has been used with no adverse effect in echidnas with ileus. Antacids, including ranitidine and omeprazole, and the mucosal protectant sucralfate have been used in cases of gastritis (see section 7.1.2). However, their efficacy is doubtful as their mode of action is centred on gastric parietal cells, which echidnas appear to lack. Ranitidine can enhance gastric emptying in domestic species (Plumb 2015). The antiemetic maropitant has been safely used in anorectic echidnas after gastrotomy.
Antidiarrhoeal suspensions and barium sulfate at 5-10 mL PO sid have been used with some success in cases of intractable diarrhoea. Low-dose lactulose is safe and effective for relieving constipation.
Oral medications or transfaunation can be given in a small amount of food for echidnas that are eating or by gavage in those that are inappetent or unable to eat effectively (see section 4.2). There is a single report of an oesophagostomy tube placed for 2 wk (Vaasjo et al. 2024).
6.6 Blood transfusion
Blood transfusions have been successfully performed in echidnas (R Booth pers. comm.; W Bergen pers. comm.). An echidna with a PCV of 6% was successfully transfused with a post-transfusion PCV of 19%, and a PCV of 38% five weeks post-transfusion.
Donor blood was collected from the beak sinus as multiple 2 ml aliquots in citrate-phosphate-dextrose-adenine primed syringes. Donor and recipient blood was crossmatched using the rapid slide agglutination method.
Blood was transfused via the lateral saphenous vein using standard small animal transfusion protocols.
7.