DISEASES

A comprehensive review of diseases of macropods is cov­ered in Vogelnest and Portas (2008). Trauma, broncho­pneumonia and dental disease (MPPD) were identified as the leading causes of mortality in a review of macropod pathology records at a North American zoo (Anderson and Dennis 2022).

4.1 Infectious diseases

4.1.1 Viral diseases

a. Retroviridae

‘Wallaby retrovirus’ was isolated from a managed popu­lation of tammar wallabies and red-necked wallabies, and caused marked cytopathic effect in a potoroo cell line (Kapustin et al. 1999). Retrovirus-associated immunodeficiency leading to opportunistic infections in the population was postulated. The seroprevalence of wallaby retrovirus in 269 macropods, representing 10 species, held in North American institutions from 1997­2005 was 20.4% (Georoff et al. 2008). Tammar wallabies had the highest seroprevalence (66%), followed by yellow­footed rock-wallabies (P. xanthopus), swamp wallabies ( Wallabia bicolor), red-necked wallabies and parma wal­labies (N. parma). A wild-caught tammar wallaby, from Kawau Is., NZ, was seropositive before contact with other macropods in North America. Kangaroos, common wal­laroos (O. robustus) and Matschie’s tree kangaroos (D. matschiei) were seronegative. The health status of sero­positive animals was not reported. The epidemiology and clinical significance of retroviruses in macropods remains unclear. The retroviral status of free-ranging populations is unknown.

b. Papillomaviridae

A free-ranging adult male brush-tailed bettong was cap­tured with multiple raised papillomatous lesions on the eyelids and muzzle (Bennett et al.

Papillomatous proliferations were observed on the skin of the tail and feet of a semi-free-ranging long-nosed potoroo (Potorous tridactylus); the lesions had resolved by the time the animal was re-examined 10 mo later (T Portas pers. comm.) (Fig. 31.1).

A putative papillomavirus was detected by PCR and sequencing in the healthy skin of 1 of 23 eastern grey kan­garoos held in managed care (Antonsson and McMillan 2006).

c. Poxviridae

Poxvirus-associated cutaneous, typically self-limiting, papillomatous proliferations have been described in macropods (Vogelnest and Portas 2008; Ladds 2009) (Fig. 31.2). The genomes of the newly proposed ‘western grey kangaroo poxvirus’ and ‘eastern grey kangaroo poxvirus’, isolated from free-ranging kangaroos in WA, and in NSW and Qld, respectively, have been character­ised (Bennett et al. 2017; Sarker et al. 2017).

d. Reoviridae

The epizootic sudden deaths of 120 tammar wallabies in managed care in multiple facilities in NSW and Qld in 1998-99, associated with orbiviruses of the Eubanangee serogroup, was presented by Rose et al. (2000) (summa­rised by Vogelnest and Portas 2008). The full

Fig. 31.1. Papillomatous proliferations on the pes of a long-nosed potoroo (Potorous tridactylus). Photo: Timothy Portas

Fig. 31.2. Poxvirus lesions on the forelimbs of an eastern grey kangaroo (Macropusgiganteus). Photo: Timothy Portas

investigation has since been published (Rose et al.

Documented outbreaks of these orbiviruses have com­menced in early summer with an association with periods of heavy rain and increased activity of biting arthropods. Mortality rates up to 60% have been reported. Diagnosis is on the basis of pathological findings and virus isola­tion. Heart, liver, intestine, cerebral cortex and cerebro­spinal fluid are the preferred samples for virus isolation (WHA 2013). Preventative measures to control arthropod vectors should be considered by institutions in affected areas during conditions favourable to disease emergence (Rose et al. 2012).

e. Rhabdoviridae

Agile wallabies (N. agilis) and kangaroos in the Mitchell River region of north Qld had a seroprevalence of 70% and 10%, respectively, to Ngaingan virus, a rhabdovirus isolated from biting midges (Doherty et al. 1973). Gubala et al. (2010) sequenced the full genome of the virus. The clinical significance of Ngaingan virus in macropods, or other species, is unknown.

f. Herpesviridae

Macropod herpesviruses are discussed in Chapter 23.

4.1.2 Bacterial diseases

Macropod progressive periodontal disease (‘lumpy jaw’) is discussed in Chapter 32.

a. Otitis

Otitis interna, media and externa, with osteomyelitis, associated with Pasteurella multocida and Klebsiella pneumoniae was diagnosed in a red kangaroo (Okeson et al. 2008). Changes in the inner and middle ear were detected with magnetic resonance imaging but not with conventional radiography.

The anaerobes Bacteroides tectus and Porphyromonas gulae were isolated from a parma wallaby with otitis and ascending meningoencephalitis (Giannitti et al. 2014). Immunohistochemical staining confirmed concurrent Toxoplasma gondii oocysts in the brain and heart.

b. Treponema

Genital infection with a Treponema sp. is recognised in all known free-ranging and managed populations of Gil­bert’s potoroos (P. gilbertii). Males present with varying degrees of ulcerative exudative balanoposthitis and cloa- citis, with mixed secondary infections; infected females variably exhibit discharge from the urogenital sinus. A period prevalence of 68% was reported in a study exam­ining 44 potoroos (Vaughan-Higgins et al. 2011). Detec­tion of spiral bacteria using dark-field microscopy was the most sensitive diagnostic test and PCR was the most specific. The spirochaetes were also observed histologi­cally with silver staining in preputial biopsies. There were no differences in haematology, biochemistry, rectal tem­perature or body condition between infected and non­infected animals but it seems likely that infection would reduce fertility/fecundity, as seen with Treponema infec­tion in rabbits. Procaine-benzathine penicillin G (84 000 IU∕kg IM q 7 d ? 3 doses) successfully resolved infection in two of three potoroos with mild-moderate disease (Vaughan 2008).

Balanoposthitis associated with a Treponema sp. has also been observed in zoo-housed long-nosed potoroos (F Hulst pers. comm.).

c. Bacteria with zoonotic potential

Zoonoses are covered in detail in Chapter 16. The preva­lence of faecal shedding of Salmonella in wild western grey kangaroos in sites across WA ranged from 0% to 9.8%; increased shedding was associated with higher rain­fall from late-autumn (Potter et al. 2011a). By comparison, Hart et al. (1985) found faecal shedding of Salmonella approached 100% during summer in wild quokkas (Seto- nix brachyurus) exposed to human activities. Martinez- Perez (2016) identified the Salmonella serovars present in Rottnest Is. and mainland populations of quokkas.

Shiga-toxigenic Escherichia coli (STEC) was detected in 7.2% of 516 faecal samples from managed and free- ranging macropods across Qld (Rupan et al. 2012). Prevalence was highest in grazing macropods, which was comparable to prevalence rates in cattle, the principle recognised reservoir of STEC.

Macropods are likely to be important in the mainte­nance and transmission of Coxiella burnetii, the aetio- logical agent of Q fever. Tolpinrud et al. (2022) validated an indirect immunofluorescence assay (IFA) and indirect ELISA for detection of antibodies to C. burnetti in macropods. Seroprevalences in populations of various kangaroo, wallaby and pademelon species from 0% to 92.4% have been reported (Banazis et al. 2010; Potter et al. 2011b; Cooper et al. 2012; Tolpinrud et al. 2022). Reported PCR prevalence of C. burnetii in faeces of free-ranging western grey kangaroos ranges from 4.1% to 12.2% (Banazis et al. 2010; Potter et al. 2011b) (see Chapter 16).

4.1.3 Fungal diseases

a. Cryptococcosis (see Chapter 25)

Cryptococcosis has been reported in a range of macropod species (Vogelnest and Portas 2008; Ladds 2009). Thurber et al. (2017) reported clinical renal amyloidosis secondary to pulmonary cryptococcosis (Cryptococcus neoformans var. grubii) in a red kangaroo.

b. Onychomycosis

Chrysosporium keratophilum was associated with severe pseudocarcinomatous swelling ± claw loss affecting hindlimb or forelimb digits in 7 of 10 managed red­necked wallabies (Pin et al. 2011). Digit four of the hindlimb was most commonly affected. Advanced cases were unresponsive to oral ketoconazole. No new cases occurred in the 6 mo following environmental cleaning and disinfection with 0.2% enilconazole q 4 wk for 4 mo. Saprophytic fungi are generally considered opportunistic pathogens. A predisposing factor, such as physical injury, could not be confirmed.

c. Rhinosinusitis

A Penicillium sp. was identified as the likely aetiological agent in a zoo-housed adult female red-necked wallaby with destructive rhinosinusitis (Rose et al. 2018). Present­ing signs included chronic left-sided facial swelling and nasal discharge. Diagnosis was achieved using CT, endos­copy, fungal culture and PCR. The wallaby was success­fully treated with surgical debridement, infusion of affected sinuses with voriconazole suspended in pluronic gel and long courses of systemic antibiotics and antifungals.

4.1.4 Parasitic diseases

a. Gastrointestinal helminths

Macropods are hosts to a highly diverse array of hel­minth parasites, with over 372 species documented (Bev­eridge and Gasser 2014). The research effort documenting the GI parasites of marsupials has been reviewed (Beve­ridge and Gasser 2014; Beveridge and Spratt 2015). Recent studies have investigated or reviewed the parasite assemblages in managed yellow-footed rock-wallabies (Sotohira et al. 2016) and red kangaroos (Lott et al. 2015) and in free-ranging populations of swamp wallabies (Beveridge 2016), rock-wallabies (Lott et al. 2012; Ver­meulen et al. 2016), eastern grey kangaroos (Cripps et al. 2015) and sympatric macropods in western Vic. (Aus- savy et al. 2011).

In most cases, in both free-ranging and managed situ­ations, there is no clinically appreciable impact of GI parasites on their macropod hosts. Managed populations invariably harbour GI parasites, yet are often not rou­tinely treated with anthelmintics. A limited number of GI parasites, including Globocephaloides trifidospicularis, G. macropodis, Hypodontus macropi and undescribed Stron- gyloides spp. have been associated with clinical disease and mortality (Vogelnest and Portas 2008).

Quantitative and qualitative faecal flotation tech­niques are routinely used to demonstrate nematode ova in macropods. Ova cannot be speciated morphologically and parasite diversity cannot be estimated beyond broad taxonomic divisions (Spratt et al. 2008). Further, there appears to be a poor correlation between FEC and abun­dance of adult nematodes. Cripps et al. (2015) found that the FEC in a population of free-ranging eastern grey kan­garoos was most dependent on the abundance of one spe­cies of nematode that represented only 7% of the total adult worm burden.

Juvenile free-ranging eastern grey kangaroos treated with albendazole (3.8 mg/kg PO, see section 2.3), with demonstrated reduction in FEC, showed no difference in growth rate, body condition or RBC parameters com­pared with untreated controls; a significant, though modest, increase in circulating albumin was found in treated animals (Cripps et al. 2014). Similarly, there was no difference in fine-scale foraging behaviour of treated (albendazole PO) and untreated adult free-ranging female eastern grey kangaroos (Cripps et al. 2016). Para­site abundance, host health and faecal cortisol metabo­lites in translocated brush-tailed bettongs were influenced by factors other than ivermectin treatment (that temporarily reduced Strongyloides-like FEC), including population density (Northover et al. 2015; Hing et al. 2017) (see section 2.3).

b. Echinococcosis

Sheep, pigs and macropods are intermediate hosts and canids the definitive hosts for Echinococcus granulosus in Australia. Cysts predominantly occur in the lungs of macropods (Fig. 31.3). Alvarez Rojas et al. (2016) reported a higher level of E. granulosus haplotype diversity across Australia than would be expected from a recent bottle­neck introduction with sheep, suggesting multiple intro­ductions since European settlement, or, introduction with dingoes up to 6000 yr earlier.

Barnes et al. (2008) reported a prevalence of 15.3% in free-ranging brush-tailed rock-wallabies, based on radio­graphic lesions. Recapture of affected animals revealed up to 43% cyst growth at 3 mo and up to 68% at 6 mo (Barnes et al. 2008). In experimentally infected tammar wallabies, cysts developed more rapidly, and were up to 6-fold larger at comparable time points, compared with sheep; 7 of 11 affected wallabies died or were euthanased on welfare grounds within 16 mo of inoculation (Barnes et al. 2007; Barnes et al. 2011). In small macropods at least, the progressive reduction in lung capacity is likely to significantly reduce fitness and is directly fatal in a proportion of cases. Echinococcosis should be considered as a potential threatening process for populations within endemic areas.

Vaccination has been successfully evaluated in tammar wallabies (see section 3.1.2).

c. Fascioliasis

Fasciola hepatica is recognised as a significant pathogen of macropods in managed care and free-ranging macro­pods within the distribution of the snail intermediate host, Gabbia tomentosa. A sylvatic cycle between macro­pods and G. tomentosa, independent of domestic

Fig. 31.3. Pulmonary hydatid cysts (Echinococcusgranulosus) in a swamp wallaby (Wallabia bicolor). Photo: Timothy Portas

Fig. 31.4. Hepatic fibrosis associated with chronic Fasciola hepatica infection in an eastern grey kangaroo (Macropusgiganteus). Photo: Timothy Portas

Fig. 31.5. Severe ulcerative haemorrhagic tracheitis associated with a heavy infestation of 2nd- and 3rd-stage Tracheomyia macropi instars in an eastern grey kangaroo (Macropusgiganteus). Photo: Timothy Portas

definitive host species, appears likely (Spratt and Presi- dente 1981; Obendorf 1983). Species variability in infec­tion tolerance among macropods has been postulated, with eastern grey kangaroos observed to harbour 1-122 flukes without apparent clinical effect. Lamb et al. (2021) reported prevalence up to 45% in eastern grey kangaroos in high risk sites in north eastern NSW based on faecal egg count (FEC), with FEC up to 195 (mean 18) eggs per gram; of 60 farms surveyed, 27% had macropods shed­ding fluke eggs in faeces. A commercial cELISA had high specificity and sensitivity for detecting fluke antigen in faeces (Lamb et al. 2021). Portas and Taylor (2015) described two free-ranging eastern grey kangaroos, euthanased with severe fascioliasis, that harboured only 18 and 36 flukes in the biliary tree, respectively. Clinical pathological changes included anaemia, hypoalbuminae- mia, azotaemia and elevated liver and muscle enzymes. In addition to typical hepatobiliary pathology (Fig. 31.4), multisystemic amyloidosis and hepatic abscessation were identified (Portas and Taylor 2015). Hepatic fascioliasis was the cause of death in two eastern grey kangaroos necropsied, of ~30 reported kangaroo deaths in a subur­ban area of south-east Qld (Nelson and Gordon 2016).

d. Bot fly myiasis

Third-stage instars of the kangaroo bot fly (Tracheomyia macropi) have been reported seasonally in the trachea and, less commonly, lower respiratory tract of macropods in eastern Australia, including red kangaroo, eastern grey kangaroo, common wallaroo, red-necked wallaby, bri­dled nail-tailed wallaby, swamp wallaby and Herbert’s rock wallaby (P. herberti) (Portas and Spratt 2008; Ladds 2009; Nelson and Gordon 2016).

The larvae are typically of low pathogenicity, with self­limiting ulcerative tracheitis associated with large burdens. Severe ulcerative fibrinosuppurative tracheitis, bronchitis and bronchiolitis with secondary bacterial infection in a free-ranging red-necked wallaby were associated with a heavy burden of bot fly larvae (Portas and Spratt 2008). Concurrent myopathy and stress of hospitalisation before euthanasia may have exacerbated the disease. Large num­bers of bot fly larvae in the trachea, with severe ulcerative haemorrhagic tracheitis, have also been observed in a hand-reared, sub-adult eastern grey kangaroo with con­current coccidiosis (T Portaspers. comm.) (Fig. 31.5).

e. Protozoa

Toxoplasmosis is discussed in Chapter 21. Haemoproto­zoa are discussed in Chapter 26.

Coccidia - Molecular characterisation of Eimeria spp. from kangaroos, tammar wallabies and quokkas (Table 31.2) revealed phylogenetic clustering with an Eimeria from mountain brush-tailed possums (Trichosu- rus cunninghami) (Power et al. 2009; Hill et al. 2012; Yang et al. 2012; Austen et al. 2014). These species form a dis­tinct clade that diverged before known placental-mammal Eimeria spp., consistent with co-evolutionary host-para­site relationships. Morphological description of a novel coccidian, Eimeria burdi sp. n., from the burrowing bet­tong (B. lesueur) has been reported (Hulst et al. 2016).

Coccidiosis in macropods is well recognised (Vogel- nest and Portas 2008). However, despite many species of

Table 31.2. Newly described species of protozoal intestinal parasites in macropods, 2008-2016

¹Yang etal. 2012 (sequences representing up to 6 new species); ²Hill etal. 2012; ³Austen etal. 2014; ⁴Hulst etal. 2016; ⁵Ryan etal. 2008; ⁶Yang etal. 2011; ⁷Vermeulen etal. 2015b; ⁸Power and Ryan 2008

Eimeria having been described in macropods, the species involved in coccidiosis cases has generally not been estab­lished. Based on oocyst morphology, two cases of coccidi­osis in 1-yr-old red-necked wallabies were associated with E. macropodis and/or E. toganmainensis (Twomey et al. 2008) and E. prionotemni (Twomey et al. 2010), respec­tively. The first case had concurrent systemic listeriosis.

Cryptosporidium - Macropods carry a range of Cryptosporidium spp., including zoonotic species; preva­lence is typically 6-12% (Vermeulen et al. 2015b). Clinical disease associated with infection has not been reported in macropods. Two macropod-associated Cryptosporidium species have been characterised (Table 31.2). One of these, C. fayeri, has been associated with GI disease in humans (Waldron 2010).

Cryptosporidium cuniculus, previously recognised only in rabbits and causing zoonotic disease in humans, was detected in the faeces of a free-ranging eastern grey kangaroo (Koehler et al. 2014). The likelihood of true infection was considered high, relative to the possibility of passive transit from contaminated pasture.

Giardia - Zoonotic assemblages of Giardia duodenalis were reported in clinically healthy managed and free- ranging brush-tailed rock-wallabies, suggesting spillover from humans and domestic animals (Vermeulen et al. 2015a).

Neospora - A zoo-housed parma wallaby in Austria was diagnosed post mortem with myocardial neosporosis (Cronstedt-Fell et al. 2012). Histologically there was mul­tifocal myocardial necrosis with mononuclear infiltrate and intracellular protozoa. Tissues were positive for Neospora caninum by immunohistochemistry and PCR, and negative for Toxoplasma gondii.

Mayberry et al. (2014) reported the prevalence of detect­able antibodies to N. caninum and T. gondii in free-ranging female western grey kangaroos in a suburban area of WA to be 20% and 18%, respectively. There was no association between serological status and reproductive success.

Protozoal rhinitis - An uncharacterised Besnoitia-like protozoan has been associated with potentially fatal epistaxis in eastern grey kangaroos and western grey kangaroos in NSW (Vogelnest and Portas 2008), and in managed western grey kangaroos in SA (Boardman et al. 2011; I Hough pers. comm.), Qld and WA (WHA 2011). Infection can be self­limiting with spontaneous recovery (W Boardman pers. comm.). Effective treatment has not been reported.

Leishmaniasis - Cutaneous leishmaniasis has been reported in various species of zoo-housed macropods in northern Australia (see Chapter 12).

Visceral leishmaniasis was reported in a zoo-housed red-necked wallaby in Spain (Ramirez et al. 2013). The liver and spleen were enlarged, with granulomatous inflammation and multifocal necrosis. Amastigotes were identified within macrophages. Immunohistochemical staining for the locally endemic Leishmania infantum was positive. Leishmania infantum was subsequently detected by PCR at necropsy in four red-necked walla­bies at a Spanish wildlife park (Montoya et al. 2016). Clinical signs consistent with visceral leishmaniasis were present in only one animal, though histopathology was not performed in this case. No clinical disease or histo­pathology consistent with leishmaniasis were identified in the other three animals.

Blastocystis - A unicellular enteric parasite of humans and other animals, Blastocystis may be a cause of chronic GI disease in humans. Blastocystis has been identified in the faeces of healthy managed and free-ranging macro­pods, including quokkas, western grey kangaroos, east­ern grey kangaroos and red kangaroos (Parkar et al. 2010; Roberts et al. 2013). The epidemiology of Blastocystis infection is poorly understood; however, based on current information it should be considered as a potentially zoonotic parasite of macropods.

Amoebiasis - Ulcerative gastritis and typhlitis with intralesional amoebic trophozoites were reported in a red kangaroo with concurrent toxoplasmosis (Ilha and Coarsey 2019). Amoebic gastritis and meningoenephalitis in macro­pods have previously been summarised (Vogelnest and Portas 2008).

4.2 Non-infectious diseases

Neoplasia and toxicoses are covered in Chapters 18 and 19, respectively.

4.2.1 Skeletal abnormalities

a. Spinal fracture

Cervical spinal fracture, particularly the 2nd cervical vertebra (C2), is a common injury associated with colli­sion events. This may be associated with poorly developed cervical muscles, weakness of the atlanto-occipital articu­lation, late (6-7 yr) physeal closure in macropods (C2 has a distinct physis between the cranial and caudal buttress) and/or incomplete ventral arch of C1 (Emerson 1983; Vogelnest and Portas 2008; Vogelnest and Allan 2015; Hulst et al. 2015). Often the injury is fatal, or necessitates euthanasia because of the severity of the injury and/or the ability of the patient to tolerate intensive management. Cervical spinal fracture with tetraparesis has been surgi­cally corrected, with return to normal function, in a juve­nile red kangaroo and an adult red-necked wallaby (Ivany and Dyce 2002; Kragness et al. 2016) (see Chapter 10).

b. Hypertrophic osteopathy

Hypertrophic osteopathy, associated at necropsy with mixed bacterial pneumonia, has been reported in a zoo­housed adult common wallaroo (Wayne and Nicholson 1999). A red kangaroo with hypertrophic osteopathy, associated with a pulmonary abscess caused by Actino­myces denticolens, was successfully treated with an extended course of antibiosis and analgesia, with clinical improvement of both conditions (Kunze et al. 2016).

4.2.2 Ophthalmic abnormalities

Unilateral anterior segment dysgenesis, consistent with Peters’ anomaly, was diagnosed by ophthalmic and ultrasound examination in a zoo-housed red kangaroo (Suedmeyer et al. 2014). A chromosomal abnormality was identified and postulated as a possible cause of the anom­aly. The kangaroo compensated adequately with the visual deficit without treatment and was excluded from the zoo’s breeding program.

4.2.3 Cardiovascular abnormalities

a. Hypertension (see section 1.1)

Multisystemic, mild to severe, arterial and arteriolar hypertrophy, consistent with hypertension, was detected in a managed population of 21 western grey kangaroos over a 14-yr period (Kagan et al. 2009). Other causes of vascular hypertrophy were excluded. Four kangaroos had antemor­tem retinal detachment, a potential sequela to hyperten­sion. There was no association with age, infectious disease, renal disease or thyroid abnormalities. Diet and other potential predisposing factors were not investigated.

b. Hypertrophic cardiomyopathy

A 3-yr-old moderately overweight male Matschie’s tree kangaroo with a short history of intermittent lethargy and tachypnoea was diagnosed by echocardiography (relative to measurements of four clinically normal con- specifics) with left-sided hypertrophic cardiomyopathy (Fredholm et al. 2015). Clinical signs were successfully controlled for more than 11 yr with enalapril PO, furo­semide PO, diltiazem PO and dietary modification to facilitate weight loss.

Two zoo-housed adult female red-necked wallabies died suddenly and were diagnosed at necropsy with marked concentric hypertrophy of the left ventricle, with­out evidence of myocardial necrosis, mineralisation or fibrosis (Stern 2010). No aetiology for the myocardial changes was identified. Both wallabies had concurrent lesions consistent with acute myopathy and/or trauma. Right-sided cardiac hypertrophy, putatively attributed to hypoxia of high altitude, was reported in an adult male red-necked wallaby at a Mexican zoo situated at an alti­tude >2000 m (Juan-Salles et al. 2015). Clinical signs, if any, were not reported. The wallaby died from other causes. Reference data for cardiac measurements and his­tology of macropods are required to assist pathological interpretation of such findings.

4.2.4 Alimentary tract abnormalities

a. Megaoesophagus

Megaoesophagus, affecting the upper 30 cm of the oesophagus, was diagnosed in a zoo-housed 13-yr-old female red kangaroo by barium-contrast radiography and endoscopy (Woodhouse et al. 2010). Clinical signs included persistent regurgitation, refractory to medical management and elevated feeding of a liquid diet. Oesophageal strictures, myasthenia gravis and persistent right aortic arch were excluded. A zoo-housed 6-yr-old red kangaroo with cervical megaoesophagus was man­aged conservatively for 6 mo, but was euthanased because of increased frequency of regurgitation, associated with acute onset depression and respiratory signs (S Vitali pers. comm.).

A brush-tailed rock-wallaby with dyspnoea and regur­gitation was diagnosed radiographically with megaoe­sophagus and euthanased (ARWH 2018 case no. 6425.1). Oesophageal dilation to approximately twice the normal diameter extended from the cervical oesophagus to the diaphragm. Myasthenia gravis, hypothyroidism and lead toxicity were excluded.

Over a 25-yr period, 22 cases of megaoesophagus (prevalence 21.1%) were diagnosed in adult parma walla­bies at a North American zoo, including in 8/8 adult wal­labies evaluated prospectively, in which dilation and delayed oesophageal transit time was confirmed by bar- ium-contrast radiography (Burgdorf-Moisuk et al. 2012). Clinical signs variably included weight loss, regurgita­tion, depression, dyspnoea and sudden death. A survey of other North American institutions identified three cases among 286 parma wallabies held over the same 25-yr period. Myasthenia gravis, lead toxicosis, toxoplasmosis and thyroid disease were excluded as causes.

b. Oesophageal diverticula

Four wild-caught parma wallabies held in managed care presented with chronic ventral neck swellings between 1 and 5 cm diameter (Okeson et al. 2009). One animal had reduced body condition. Oesophageal diverticula, with food impaction, were diagnosed by palpation, radiogra­phy and flexible endoscopy. Two animals underwent sur­gery (see Chapter 10), one of which was successful; two were managed conservatively with dietary modification. Two wallabies developed pneumonia, potentially a conse­quence of aspiration. No consistent underlying cause was identified. Cases were variably associated with oesopha­geal stricture, adjacent unilateral thyroid ectasia and hyperplasia, and ectopic thyroid tissue in the oesophageal wall with mucosal necrosis and ulceration.

Dilatation of the cranial thoracic oesophagus has been associated with oesophagitis and respiratory distress in western brush wallabies (N. irma). A degree of sacculation of the cranial intrathoracic oesophagus has been observed in clinically normal wallabies and may be a normal anatomical feature in this species; the extent of dilatation appears more pronounced in clinically affected individuals, with retained ingesta radiographically visible within the thoracic cavity (S Vitali pers. comm.).

c. Intestinal diverticula

An 8-yr-old swamp wallaby died after a short period of acute onset depression, anorexia and presumed abdomi­nal pain (Haist et al. 2012). Four 7-8 cm long saccular dilatations were present in the jejunal wall, with longitu­dinal rupture of the muscular layer, mucosal herniation and a series of perforations resulting in fibrinosuppura- tive peritonitis. Lesions resembled colonic diverticulosis in humans, which is typically asymptomatic.

A fluid-filled abdominal mass associated with the small intestine was excised by resection and anastomosis from an adult male brush-tailed rock wallaby and diag­nosed histologically as an intestinal diverticulum (ARWH 2018 case no. 4283.1). The wallaby was eutha­nased after 3 d because of postoperative complications.

d. Mesenteric and gastrointestinal volvulus (see Chapter 10) Mesenteric volvulus has been reported in adult male red kangaroos (Knafo et al. 2014; ARWH 2018 case no. 11760.1), western grey kangaroos (Stern 2010; J Weller pers. comm.) and a brush-tailed rock-wallaby (ARWH 2018 case no. 6450.1). One of the red kangaroos had a 2-wk history of vomiting and anorexia, and short infre­quent episodes of vomiting in the 12 mo prior. It was diagnosed with gastric dilation-volvulus, splenic dis­placement and generalised megaoesophagus by CT with IV contrast. Swirling strands of mesentery and fat (the ‘whirl sign’) were evident around the coeliac and cranial mesenteric arteries, and the oesophagus. Volvulus was corrected surgically and gastropexy performed to pre­vent recurrence (Knafo et al. 2014). In another case, a large adult male red kangaroo was found dead with no prior clinical signs and diagnosed at necropsy (ARWH 2018 case no. 11760.1). One western grey kangaroo died acutely with no prior clinical signs and was diagnosed at necropsy; another presented with acute progressive abdominal pain subsequent to a 2-mo history of weight loss and uncharacteristic recumbency and was diag­nosed and reduced at exploratory laparotomy (J Weller pers. comm.). The red and western grey kangaroos treated surgically appeared to respond well initially but were euthanased 2-12 wk later because of progressive anaemia (possibly gastric ulceration) or recurrence of severe abdominal pain. The brush-tailed rock wallaby was found dead and diagnosed at necropsy (ARWH 2018 case no. 6450.1).

The cause of mesenteric volvulus in macropods is unknown. In other species, primary or secondary disrup­tion to GI motility is often hypothesised, though in many cases no cause is identified. Knafo et al. (2014) postulated aerophagia, altered GI flora and subsequent gas disten­sion and ileus, secondary to pain and anorexia associated with a tooth root abscess, as possible predisposing factors in a red kangaroo.

Gastric volvulus was diagnosed in a whiptail wallaby (N. parryi), yellow-footed rock-wallaby and brush-tailed rock-wallaby (also involving the spleen) that were found dead, euthanased and died during surgery, respectively (ARWH 2018 case nos 1584.1, 4897.1, 11315.1). Toxoplas­mosis was associated with gastric volvulus in a hand­reared whiptail wallaby (T Portas pers. comm.). The wallaby was euthanased 2 d after surgical correction. Tachyzoites were evident histologically in in the GIT. Small intestinal torsion and liver lobe torsion have been reported in kangaroos (Stern 2010).

e. Gastrointestinal foreign bodies

Gastric and intestinal trichophytobezoars causing duode­nal obstruction were successfully removed surgically from an 11-mo-old red-necked wallaby (see Chapter 10). The wallaby presented acutely with lethargy, anorexia and ataxia. Gaseous gastric distension was identified on plain radiographs. The bezoars were subsequently identi­fied with CT. The contributing factors to the development of trichophytobezoars in this case were not definitively identified.

4.2.5 Mesenteric fat necrosis

Four zoo-housed quokkas were diagnosed with necrosis of mesenteric and retroperitoneal fat deposits (Hulst et al. 2010). Some masses were mineralised, with metaplastic bone and bone marrow formation. Two quokkas died of the disease; two others diagnosed radiographically remained asymptomatic. Ingestion of a meat-based echidna diet in the mixed-species habitat was postulated as a possible cause. Another Australian zoo found radio­graphic evidence of mineralised mesenteric fat necrosis during routine health examinations of asymptomatic overweight quokkas housed in a walk-through habitat with public feeding.

4.2.6 Xanthomatosis

Multicentric xanthomas were identified in two of five zoo-housed long-nosed potoroos maintained for 2 yr in a walk-through mixed-species aviary with access to foods including meat mix and sunflower seeds (L Wicker pers. comm.). Animals presented with multiple small, round, slightly raised dermal lesions on fore- and hindlimb foot pads. One animal developed respiratory noise associated with a large oropharyngeal xanthoma. Pericardial xan­thomas were identified in both animals at necropsy. Both potoroos had elevated cholesterol concentrations com­pared with unaffected animals.

4.2.7 Urolithiasis

Reports of urolithiasis in macropods are outlined in Table 31.3.

Lindemann et al. (2013) reported calcium carbonate uroliths in both ureters and the urethra in a zoo-housed red kangaroo with hydronephrosis, hydroureter and rup­tured bladder. Ureteroliths were visible radiographically. Dietary analyses suggested excessive calcium intake from excessive intake of alfalfa (lucerne) leaf. High cal­cium intake with alfalfa hay was also proposed as a likely cause of 15 cases of urolithiasis (calcium carbonate in most cases) in zoo-housed tammar wallabies over an 8-yr period (Liptovszky et al. 2014). Alfalfa hay was replaced with grass hay in the diet and there were no cases in the subsequent 7 yr (M Liptovszky pers. comm.).

A zoo-born tammar wallaby, taken for hand-rearing at 6 mo old, presented at 8 mo with pyuria and struvite crystalluria. After 3 d of intensive care, the distal urethra became obstructed with a plug of grainy pasty material; cytology revealed amorphous cellular and mucous debris, but no crystals. Marsupialisation of the bladder contributed to successful resolution (see Chapter 10).

A 10-mo-old zoo-housed red kangaroo presenting for licking at an erythematous penis was diagnosed with calcium magnesium carbonophosphate urolithiasis with stones accumulating in the trigone of the bladder (McCready et al. 2023). A urethral catheter was placed under general and spinal anaesthesia to relieve the obstruction, and the stones removed via cystotomy. The authors noted that it was relatively easy to pass the cath­eter to the bladder, contrary to previous reports in macropods, and speculated whether spinal anaesthesia and/or the young age of the kangaroo may have contrib­uted to this.

Table 31.3. Urolithiasis reported in macropods

¹Plimmer 1915; ²Plimmer 1916; ³Hamerton 1933; ⁴Clark etal. 1982; ⁵Bryant and Rose 2003; ⁶Lindemann etal. 2013; ⁷Liptovszky etal. 2014

4.2.8 Endocrinopathies

Hypoaldosteronism was diagnosed by ACTH-stimula­tion in a 20-yr-old Matschie’s tree kangaroo with hyponatraemia, hyperkalaemia, hypercalcaemia and non-specific clinical signs (Whoriskey et al. 2016). Clinical signs and electrolyte abnormalities improved with desoxycorticosterone pivalate 2.4 mg/kg IM q 25 d, adjusted over time based on electrolyte monitoring.

4.2.9 Amyloidosis

Hepatic, splenic and intestinal amyloidosis, considered secondary to chronic inflammation caused by Fasciola hepatica infection, were diagnosed in a free-ranging adult female eastern grey kangaroo (Portas and Taylor 2015). Renal amyloidosis resulting in hypoproteinaemia, subcu­taneous oedema and internal effusions was diagnosed in a zoo-housed red kangaroo with chronic pulmonary crypto­coccosis (Thurber et al. 2017). A zoo-housed sub-adult female eastern grey kangaroo, euthanased because of leth­argy and poor body condition, was diagnosed postmortem with extensive systemic amyloidosis associated with almost complete loss of normal hepatic architecture; a chronic ocular foreign body was considered a possible cause of the amyloidosis. Attempts to characterise the type of amyloid involved using immunohistochemical techniques devised for humans were unsuccessful (T Portas pers. comm.).

Amyloidosis was diagnosed in 15 macropod cases in the Australian Registry of Wildlife Health database (ARWH 2018). Eight of these cases were eastern grey kan­garoos; other species affected included western grey kangaroo, antilopine wallaroo (Osphranter antilopinus), parma wallaby, yellow-footed rock-wallaby and quokka. The spleen was the most common affected site; other tis­sues with amyloid deposition included liver, kidney, adre­nal gland, pancreas and parathyroid gland. Concurrent inflammatory disease was most commonly identified in the GIT and kidney.

4.2.10 Malnutrition

Portas et al. (2016) investigated a winter mortality event of ~200 predominantly sub-adult eastern grey kangaroos, during a period of increased kangaroo mortality across the ACT. Affected kangaroos were emaciated and weak. Clinical pathology variably demonstrated anaemia, hypoalbuminaemia, mild azotaemia, elevated CK and/or low triglycerides. Necropsy findings in 10 kangaroos included gastric mucosal ulceration and enteric coccidio- sis; 11 GI helminth species were variably present, includ­ing G. trifidospicularis. A proportion of kangaroos were PCR positive for Trypanosoma spp., Theileria penicillata and Cryptosporidium macropodum. Mortalities were attributed to starvation from low pasture biomass, but endoparasitism and cold overnight temperatures were considered contributing factors.

4.3 Syndromes of uncertain aetiology

4.3.1 Mortality events in free-ranging macropods

In Lake Macquarie, NSW, 350 eastern grey kangaroos died over a 3-mo period with weakness, epistaxis, neuro­logical signs and pinpoint mucosal haemorrhages.

Fig. 31.6. Typical keratitis and mucopurulent conjunctivitis observed in a syndrome of unknown aetiology in an eastern grey kangaroo (Macropus giganteus) from SE Qld. Photo: Timothy Portas

Extensive multisystemic haemorrhage was found at nec­ropsy. Babesia-like organisms were identified, but the association with death was unclear (Arthur et al. 2014).

Periodic kangaroo mortality events in western NSW and Qld have been associated with increased insect activ­ity. Necropsy of four kangaroos in 2010 identified mild non-suppurative choroiditis, though the event was incon­sistent with an epidemic of Wallal blindness in 1994-96 (Grillo 2010).

4.3.2 Keratitis, conjunctivitis and necrotic dermatitis in eastern grey kangaroos

A syndrome characterised by keratitis, uveitis, mucop­urulent conjunctivitis, nasal mucocutaneous ulcera­tion, coagulative necrosis of the epidermis and dermis, chronic hepatocellular necrosis with leucocytic infiltra­tion and patchy pulmonary congestion was observed in seven eastern grey kangaroos from Wacol in SE Qld between 2016 and 2017 (Fig. 31.6) (T Portas pers. comm.). Meningitis was evident in two animals. Affected animals were in poor body condition and appeared blind. One male kangaroo exhibited opistho­tonus, head shaking and hyper-responsiveness to exter­nal stimuli. Primary photosensitisation was considered a likely differential diagnosis, but an aetiological agent was not identified.