APPROACH TO MAMMALIAN SKIN DISEASE

1.1 History

History relevant to each patient is the critical first step in the diagnostic approach to any dermatosis, with clues often evident to guide the more likely differential diagnoses.

1.2 Clinical examination

Clinical examination is the important second step in a diagnostic evaluation. Full body examination is always indicated because systemic illness may underlie skin dis­ease. Although skin lesions cannot be considered in isola­tion, and many diseases with contrasting aetiology can produce similar clinical lesions, lesions can provide useful clues to the more likely differential diagnoses. Pri­mary lesions (e.g. papules, pustules, vesicles, nodules) are more useful than secondary lesions (e.g. erythema, crust­ing, scaling, erosions, ulceration). The comparative fre­quency of occurrence of skin lesions as predominant

Table 12.1. Comparative frequency of occurrence of skin lesions as predominant findings in varying skin disease aetiologies

Skin lesions (as predominant findings)

^aAssuming lesion distribution is not consistent with external or self-trauma.

B = bullous diseases (e.g. bullous pemphigoid, epidermolysis bullosa); C = common lesion; D = Demodex spp. only; L = less common lesion (typically concurrent with other lesions); P = pemphigus disease complex; Pn = panniculitis; SCC = squamous cell carcinoma; U = uncommon lesion.

findings in relation to varying aetiologies is shown in Table 12.1.

1.3 Diagnostic testing

The most appropriate diagnostic tests for each presenta­tion are guided by the more likely differential diagnoses, based on initial collation of history and clinical examina­tion details. Despite a tendency to rely on diagnostic test results for a diagnosis, test results can be non-specific or at times misleading, and interpretation in light of history and clinical findings is essential. Useful tests for evalua­tion of mammalian dermatoses are outlined in Table 12.2.

1.3.1 Evaluation of skin samples for infectious agents

The normal microbiota of most Australian mammal spe­cies is unknown; however, extrapolating from humans and domestic mammals, it is likely to be dominated by Staphylococcus spp. adapted to the host.

• Bacteria - very sparse on normal skin surface samples, and absent in most oil immersion fields (?1000 magni­fication) as required for accurate recognition (Fig. 12.1), despite being readily cultured from skin surface swabs that sample larger areas. Intracellular bacteria, typically cocci, within neutrophils and/or macrophages is con­sistent with infection (Plate 12.1); increased numbers alone represent overgrowth.

• Fungi - skin surface samples may reveal normal microbiota (e.g. Malassezia spp.), environmental con­taminants (e.g. moulds such as Penicillium, Aspergil­lus, Fusarium) (Fig. 12.2) or pathogens (e.g. dermatophytes). Fungal hyphae with tissue invasion and associated inflammation confirms infection. Single spores are often contaminants. Normal species and number of skin yeasts in Australian mammals are unknown.

• Microbial culture for bacteria or fungi - ideally per­formed from fine needle aspirates of nodular areas or from sterilely collected tissue biopsies.

Fig. 12.1. Normal keratinocytes on an adhesive tape impression: note their polyhedral shape, numerous small ellipsoid melanin granules on the central keratinocyte, some irregular particulate background matter and lack of bacteria (larger, distinctly rod­shaped or coccoid), consistent with the majority of oil immersion fields on normal skin (?1000 magnification; ?100 objective).

Table 12.2. Useful tests and sampling methods for evaluation of mammalian dermatoses

^aNormal skin histology is described for gliders and a dunnart (Rosenberg and Rose 1999), pinnipeds (Khamas etal. 2012), cetaceans (Miller etal. 2011; Morales-Guerrero etal. 2017), and the dugong (Dugong dugon) (Bryden etal. 1978).

^bBiopsies for microbial culture require sterile technique; pending histopathology results, tissue culture samples can be held refrigerated in a sterile container on a sterile saline-moistened swab. Biopsy samples can also be retained frozen for potential PCR or other molecular testing.

because of skin surface microbiota and contaminants; culture of an organism from the skin surface does not confirm any role as a pathogen.

• PCR testing - ideally from sterilely collected tissue biopsies; also from formalin-fixed samples if the samples remain within the fixative for for more severe presentations or when initial testing is non-diagnostic. Skin biopsies are often less helpful, as changes are non-specific for many causes, including health and husbandry, and infectious agents may be sparse. However, biopsies provide further information when a diagnosis is uncertain.

2.1.1 Ectoparasites

a. Mites

Mites account for the majority of skin disease reports in Australian mammals. Many mite infestations produce papules as the dominant early lesion. Patchy alopecia and variable degrees of erythema and moist exudation reflec­tive of self-trauma may also occur. Pruritus varies from intense (e.g. Sarcoptes spp.) to inapparent.

Demodex spp. mites are host-specific normal inhabit­ants of the skin surface, hair follicles and/or sebaceous glands in low numbers in most mammals. Disease (demodicosis or demodectic mange) is caused by over­population of mites, is rare and usually associated with immunosuppression. Single or multifocal regions of well- demarcated alopecia are typical. Nodular lesions occur in some hosts (e.g. quolls). Pruritus is usually absent to mild. Demodicosis is reported in:

• Koalas (Phascolarctos cinereus): unidentified Demodex spp.; well-demarcated periocular alopecia (Vogelnest et al. 2000)

• Dasyurids

• Agile antechinus (Antechinus agilis): Demodex tor- tellinoides - alopecia of dorsal neck and crusting of legs, feet (Desch and Holz 2006); D. antechini - nodules on head, limbs, rump, ventral abdomen (Holz 2008); early reports in the brown antechinus (A. stuartii) were later corrected to be in agile ante­chinus (Desch and Holz 2006; Lorch et al. 2007)

• Dibblers (Parantechinus apicalis), greater hairy­footed dunnart (Sminthopsis hirtipes), and kaluta (Dasykaluta rosamondae): Demodex spp. - nodules, on the face in dibblers and unspecified location in other species (Holz 2008)

• Spotted-tailed quoll (Dasyurus maculatus):

Demodex spp. - single nodules on digits and abdominal wall (Holz 1998)

• Dingo (Canis familiaris): D. canis - localised facial alopecia, generalised alopecia

Sarcoptid mites cause intensely pruritic, alopecic and scaling dermatitis (scabies or sarcoptic mange) in multiple mammalian species. Many infections are caused by a single heterogeneous species, Sarcoptes scabiei. Recent phylogenetic studies suggest S.

16.5 d in winter months (Browne et al. 2021). They have host preferences, but can cause at least transient disease in a range of host species.

Significant disease prevalence, morbidity and mortal­ity is recognised in free-ranging bare-nosed wombats (Vombatus ursinus) (regarded as the major debilitating infectious disease of this species), and southern hairy­nosed wombats (Lasiorhinus latifrons) (Borchard et al. 2012; Ruykys et al. 2013; Old et al. 2017; Bains et al. 2022). Similar bacterial microbiota changes are documented in free-ranging bare-nosed wombats as for other species infected by sarcoptic mange, with a loss of diversity of bacterial microbiota, and an increased prevalence of potentially pathogenic taxa including Staphylococcus sciuri and Corynebacterium spp. (Nvsborg-Xieisen et al. 2022). The immune response to S. scabiei in wombats appears similar to that in other hosts, with mite survival and multiplication enhanced in thickly scaled areas. The typical clinical signs in all animals are early papules and self-trauma lesions, including alopecia and excoriations, which progress to prominent scaling. Chronic infections present with marked scaling forming dense sheets and focal fissuring. Scabies is reported in:

• Agile wallaby (Notamacropus agilis): S. scabiei - thick scaling with fissuring on cranial or caudal regions or generalised (McLelland and Youl 2005); swamp

Fig. 12.3. Sarcoptic mange in a bare-nosed wombat (Vombatus ursinus). Note the prominent scaling on the face and pinna. Photo: Timothy Portas

wallaby (Wallabia bicolor): S. scabiei - thick scaling with fissures on head and shoulders (Holz et al. 2011); Macropodicoptes mironovi - alopecia, crusting and papules on medial thighs (Portas et al. 2009; Bochkov 2012)

• Koalas: S. scabiei - thick scaling with fissures on limbs, ventral trunk and face; outbreaks reported (Speight et al. 2017); Notoedres cati - likely from a domestic cat (Kwak and Reed 2017)

• Bare-nosed wombat: S. scabiei - thick scaling with fis­suring on cranial regions or generalised (Borchard et al. 2012) (Fig. 12.3); southern hairy-nosed wombat: S. scabiei - severe scaling on head, neck, shoulders (Ruykys et al. 2013; Old et al. 2017)

• Spotted-tailed quoll: Diabolicoptes major, Labidopygus australiensis and possibly Dasyurochirus major - alopecia, erythema, scaling on face, limbs, rump, tail (Vilcins et al. 2008); Tasmanian devil (Sarcophilus harrisii): Diabolocoptes sarcophilus - alopecia on rump and tail (Vilcins et al. 2008); Satanicoptes armatus in one zoo-housed animal in London (Fain and Laurence 1975)

• Eastern ring-tailed (Pseudocheirus peregrinus) and common brush-tailed possums (Trichosurus vulpec­ula): S. scabiei - unspecified skin lesions (Johnson and Hemsley 2008); Trichosurus spp.: Notoedres muris - crusty lesions on the face, pinnae and tail (Johnson and Hemsley 2008)

• Southern brown bandicoot (Isoodon obesulus): S. scabiei - alopecia, thick scaling and fissuring on the rump, caudal thighs, and tail in one free-ranging animal (Wicks et al. 2007)

• Dingo: S. scabiei - alopecia, scaling, and focal fissur­ing in free-ranging animals, seldom as a debilitating disease (Hulst 2008)

Environmental mites reside in a variety of environ­mental niches and populations may rapidly expand when conditions are favourable (often late summer/autumn in temperate areas), causing seasonally recurrent dermatitis. Lesions are typically clustered papules, which may be crusted or crateriform with a central depression, usually affecting more sparsely haired ventral axillary, inguinal or medial antebrachial areas. Trombiculid mites (chigger or scrub-itch mites) live in pasture and natural vegeta­tion; adults and nymphs are non-parasitic; larval stages may feed on mammals. Dermanyssid mites (bird mites) reside on birds, and nymph stages may feed on mammals. Environmental mite dermatitis is reported in:

• Rufous (Aepyprymnus rufescens), brush-tailed (Bet- tongia penicillata) and eastern (B. gaimardi) bettongs: Thadeua greeni - crusting, scaling and alopecia (Portas et al. 2015 and references therein)

• Eastern grey kangaroo (M. giganteus): unspecified mite species (Portas et al. 2009 and references therein)

• Yellow-footed rock-wallaby (Petrogale xanthopus): Odontacarus adelaideae; bridled nail-tailed wallaby (Onychogalea frenata): Eutrombicula hirsti; agile wallaby: unspecified species (Portas et al. 2009 and references therein); black-striped wallaby (N. dorsalis), Proserpine rock-wallaby (P. persephone), swamp and red-necked wallaby (N. rufogriseus): Thadeua serrata (Spratt et al. 2008); brush-tailed rock-wallaby (P. peni- cilliata): novel Thadeua spp. (Barnes et al. 2010); all wallabies commonly have classical papular lesions (Fig. 12.4)

• Northern brown bandicoot (Isoodon macrourus): moderate to severe pyogranulomatous hyperplastic dermatitis associated with trombiculid mites (Reiss et al. 2015)

• Brown antechinus: numerous trombiculids and dermanyssids including Mesolaelaps sminthopsis, Haemolaelaps, Telemachus, Cryptonyssus spp., Gunthe- ria shieldsi, G. derricki, G. scaevola, Neotrumbicula novaehollandiae - unspecified lesions (Lorch et al. 2007)

• Spotted-tailed quolls: unspecified mite species and lesions (Vilcins et al. 2008)

• White-footed dunnart (S. leucopus): Guntheria weedunnarti (Goff 1980)

• Bush rat (Rattus fuscipes): larvae of trombiculid mites (L Vogelnest pers. comm.)

Fur mites are parasitic mites that reside on hair shafts and surface scale on hosts. Some are host-species specific. Infestation is reported in:

• Koala: Koalachirus perkinsi - usually very low numbers and asymptomatic, outbreaks have been reported, affecting several animals with large numbers of mites, occasionally seen in single animals. Pruritus and partial alopecia in areas where the koala can reach (Blanshard and Bodley 2008; L Vogelnest pers. comm.)

• Spotted-tailed quoll: Myocoptes musculinus - found with other mites in regions of alopecia, erythema, scaling (Vilcins et al. 2008)

• Rodents (in managed care): Myocoptes leptotrombid- ium, Cheyletiella spp., Radfordia spp. and Murichuris spp. - alopecia, excoriations, crusting, ulceration (Breed and Eden 2008)

Laelaptid mites (related to dermanyssid mites) reported in:

• Common and mountain (T. cunninghami) brush­tailed possums: Trichosurolaelaps crassipes - com­pletes its entire life cycle on the host (Clark 1995), alopecia and irritation of the rump, and less frequently the head, pinnae and extremities, in some possums, while others unaffected (Johnson and Hemsley 2008)

Fig. 12.4. Clustered papules from environmental mite infestation in a brush-tailed rock-wallaby (Petrogalepenicillata). Photo: Larry Vogelnest

• Rodents (in managed care): Laelaps spp., Mesolaelaps spp. - alopecia, excoriations, crusting, ulceration (Breed and Eden 2008)

Psoroptid mites (Petauralges spp.) were associated with alopecia and scaling on the dorsal rump of a zoo­housed eastern barred bandicoot (Perameles gunnii) (Melbourne Zoo 2006 case no. MZ910320).

Tropical rat mites (Ornithonyssus bacoti) were thought to contribute to alopecia in a managed colony of greater bilbies (Macrotis lagotis).

Diagnosis of parasitic mites is often achieved with skin scrapings. Demodex spp. are usually readily detected, with characteristic elongated appearance; follicular spe­cies are longer than stratum corneal species. Superficial mites may be sparse in some presentations. Sarcoptic mites are usually plentiful, especially in heavily scaled lesions, with characteristic large, round appearance. Scraping over larger areas and PCR testing of skin scrap­ings can increase sensitivity of testing (Fraser et al. 2018a). A faster point-of-care DNA test (loop mediated isothermal amplification; LAMP) with higher sensitivity is also reported (Fraser et al. 2018b). Environmental mites may be easily detected on skin scrapings, but may be absent in some animals with skin lesions; classical papular lesions on animals residing in affected geograph­ical areas and appropriate seasons are suggestive. Fur mites may be more readily detected on unstained adhe­sive tape impressions.

Treatment of parasitic mites. Systemic macrocyclic lactones (e.g. ivermectin, moxidectin) have been effec­tive and safe in a wide range of mammals, typically dosed at 200-300 μg∕kg PO or SC q 7-10 d for three treatments. Higher dosage is generally required to treat demodicosis. Treatment is less effective in free-ranging animals, as multiple treatments of all exposed animals is required because mites can survive off-host for at least 3 wk in suitable environments (e.g. wombat bur­rows) and reinfect animals. Duration of systemic treat­ments may need to be extended for severe infections with thick scaling. Potential toxicity is well reported with higher doses in domestic species and is more likely in young or debilitated animals. Drug interactions are also reported; notably with spinosad and ketoconazole. Toxicity to ivermectin is reported in one species of Asian bat and it has been recommended to avoid use in Australian bats (Olsson and Woods 2008). Safe use of systemic macrocyclic lactones is reported in many Australian mammals (Vogelnest and Woods 2008; Death et al. 2011; Ruykys et al. 2013; Portas et al. 2015; Takano et al. 2023; see Appendix 4):

Topical miticidal agents include:

• Moxidectin - (5 mg/ml Cydectin Pour-On, Virbac Australia, Milperra, NSW - 10 to 200 ml per adult wombat, q 7 d for 3-4 doses); variably effective for treatment of sarcoptic mange in free-ranging bare­nosed wombats, applied in the field by wildlife carers (Old et al. 2021)

• Selamectin - (6 mg/kg q 14-28 d is effective for mites except Demodex spp.) and use is reported in echidna, macropods, dasyurids, possums and rodents

• Combined moxidectin and imidacloprid - q 14-28 d is effective for mites (low efficacy for Demodex spp.); use in Australian mammals appears unreported

• Fipronil - 6-10 mg/kg as a topical spot-on or full-body spray, q 7-14 d is effective for mites (except Demodex spp.). Use is reported in echidna, macropods, dasyu- rids, bandicoots and rodents. Toxicity has not been reported in native mammals; however, notable toxicity is reported in rabbits, therefore should be used with caution in native species where use is not reported

Isoxazolines (afoxolaner, fluralaner, sarolaner) are newer products recently available with high safety and efficacy against fleas, ticks and mites, including Demodex spp., in domestic dogs and cats. They are potent inhibi­tors of γ-aminobutyric acid-gated chloride and l-gluta- mate-gated chloride channels, with apparent high safety margins of oral and topical formulations in dogs, and topical formulations of fluralaner and sarolaner in cats, and increasing use in non-domestic species (Takano et al. 2023). The long half-life of fluralaner in particular has tremendous potential advantages for treatment of free- ranging mammals. Plasma levels were detectable for more than 90 d from a single topical treatment in bare-nosed wombats, which was effective and safe (at both standard 25 mg/kg dosing, and high 85 mg/kg dosing) for treat­ment of sarcoptic mange in three wombats. Diluting into suitable volumes for remote drug delivery was also evalu­ated (Wilkinson et al. 2021). Effective fluralaner treat­ment of sarcoptic mange in wombats, and also possums and koalas, is also reported anecdotally, and wildlife treatment guidelines updated accordingly. Efficacy and safety of fluralaner is reported for treatment of sarcoptic mange in wombats (Wilkinson et al. 2021). Guidelines for the use of fluralaner for treatment of sarcoptic mange in wombats report one treatment should resolve infection in bare-nosed wombats, with the large dog size of Bravecto® Spot-on (Merck Sharp and Dohme, Macquarie Park, Australia) suitable for adult wombats. The dog for­mulation is now permitted by the AVPMA for use in wombats. However, the complexity of treatment for free- ranging individuals is important to consider, due to con­tagion, co-morbidities, and dispersed populations (Carver 2021; Skerratt et al. 2021a, 2021b).

Environmental mite dermatitis can be more challenging to treat than other mite infections, as adult mites survive in the environment, or on other host species that may be widely distributed, and do not need to feed on the mammal host for survival. Sustained treatment of the affected ani­mals with repellent parasiticides (e.g. synthetic pyrethroids) may be required. Synthetic pyrethroids, including perme­thrin, are effective in dogs, but toxic in cats.

b. Fleas

Fleas are exclusive blood-feeding insects that often com­plete their life cycle on specific animal hosts, although some species are less selective. There are numerous native flea species that parasitise native Australian mam­mals; most are host-specific and do not cause disease (Spratt et al. 2008; Vogelnest and Woods 2008). Flea outbreaks may be associated with anaemia, particularly in small host species, and skin irritation is almost exclu­sively caused by adult flea feeding, with hypersensitivity to flea saliva well recognised in domestic cats and dogs. The only flea species known to complete its entire life cycle on a mammalian host is Uropsylla tasmanica, which parasitise dasyurids in Tas., with eggs glued onto hairs and a unique parasitic larval stage, with specialised spines, that enable burrowing into skin, most frequently on the groin, rump and hindlimbs. Resultant papules, irritation and self-trauma including alopecia are reported (Holz 2008; Spratt et al. 2008). Various Echidnophaga spp. (‘stick-fast’ fleas) are found on a range of Australian native mammals (Vogelnest and Woods 2008). They are not usually associated with skin disease. The domestic cat flea, Ctenocephalides felis, can potentially parasitise a variety of Australian mammals; infestation has been reported in koalas (Blanshard and Bodley 2008). Skin disease associated with flea infestation is reported in macropods (Vogelnest and Portas 2008), dasyurids (Holz 2008; Spratt et al. 2008; Vilcins et al. 2008) (32 species of fleas reported), bandicoots (Lynch 2008) and dingoes (Hulst 2008).

Treatment options for fleas include fipronil and selamectin. Imidacloprid has also been reported as effec­tive in macropods (Vogelnest and Portas 2008), eastern quolls (D. viverrinus), fat-tailed dunnarts (S. crassicau- data), yellow-bellied gliders (Petaurus australis) (Baker and Beveridge 2001; Holz 2008), Leadbeater’s possums (Gymnobelideus leadbeateri), eastern ring-tailed possums (Baker and Beveridge 2001; Johnson and Hemsley 2008) and bandicoots (Lynch 2008).

Treatment of the immature flea stages in the environ­ment (cleaning, insect growth regulators) will hasten response to animal treatment. Lufenuron has been reported as effective for flea control in closed populations of macropods (Vogelnest and Portas 2008). The new isoxazolines also appear very effective at controlling fleas in dogs and cats (see miticidal treatments) and Bravecto (MSD Animal Health Australia, Bendigo, Vic.) has been reported as effective for flea control in Tasmanian devils (L Vogelnest pers. comm.).

c. Lice

Lice are obligate host-specific parasites that spend their entire life cycle on the host; transmission requires direct animal contact. Species may be biting or sucking, which influences treatment options. Louse infestations (pedicu­losis) are often asymptomatic and many species have been described in Australian mammals (Vogelnest and Woods 2008). However, lice have not been reported on mono- tremes or bats nor on cetaceans, despite regular reference to crustaceans (Cyamus spp.) as ‘lice’. Dermatitis associ­ated with lice is most common in free-ranging animals, typically causing patchy alopecia, fur matting and varia­ble self-trauma lesions, and is reported in macropods, dasyurids and dingoes (Spratt et al. 2008; Vogelnest and Woods 2008; Portas et al. 2009).

Diagnosis of pediculosis requires close examination of the hair coat. Microscopic examination on adhesive tape samples allows distinction of biting lice (larger rounded head) and sucking lice (smaller pointed head). Eggs of both types may be evident attached to hairs.

Treatment of pediculosis is generally straightforward. Macrocyclic lactones are effective for sucking lice and fipronil for both sucking and biting species. All exposed animals of the same species need to be treated concur­rently, and treatment beyond the 3-wk life-cycle is required to resolve.

d. Ticks

A wide range of tick species has been recorded on Aus­tralian mammals (Vogelnest and Woods 2008). Ticks have strong host-preferences but lack host-specificity. Mammals are most frequently parasitised by hard ticks (ixodid), which have a hard shell and specialised mouth­parts to enable attachment to hosts for 4-14 d of feeding. In terms of dermatoses, most infestations are asympto­matic or may cause focal inflammation and craters at attachment sites. Dermatitis caused by ticks is reported in short-beaked echidnas (Tachyglossus aculeatus), macro­pods, wombats, dasyurids and bandicoots (Blanshard and Bodley 2008; Booth and Connolly 2008; Bryant and Reiss 2008; Middleton 2008).

Treatment of ticks may need to vary with the tick spe­cies. Macrocyclic lactones are often effective, but some species such as Ixodes holocyclus can be less responsive. Fipronil is often effective and the new isoxazolines are highly effective in domestic dogs, and one fluralaner dose provided apparent tick control for 15 wk in bare-nosed wombats (Wilkinson et al. 2021). Effective tick treatments in Australian mammals include fluralaner, ivermectin, moxidectin, fipronil, selamectin and amitraz rinse (see Appendix 4).

e. Flies

Several species of flies live within the fur of a small number of Australian mammal taxa (Spratt et al. 2008). Biting flies (Austrosimulium pestilens, Simulium ornatipes) may cause irritation and localised dermatitis in macropods, typically associated with heavy rain or flood­ing (Vogelnest and Portas 2008). These small black flies typically feed on the head (periocular, pinnae, muzzle), causing irritation and head-shaking, and vision may be impaired by severely swollen periocular areas. Severely affected animals are frequently isolated and lethargic. The application of topical pyrethrin-based insect repel­lents is effective in providing short-term relief. The use of environmental pyrethrin-based insecticides on shelters and night houses during periods of extensive fly activity may be an effective preventative strategy.

Cutaneous myiasis is reported in injured or debilitated koalas, associated with wound exudation, urine soiling or diarrhoea, with the pouch, conjunctival sac, external ear canal and perineum as potential sites. It is also reported in free-ranging common brush-tailed and eastern ring­tailed possums associated with wounds, where use of commercial fly-strike preparations has been anecdotally fatal. Physical removal of larvae, with appropriate wound cleaning and hygiene, is safe and effective (Vogelnest and Woods 2008).

2.1.2 Fungal diseases

a. Candidiasis

Candidiasis occurs because of overgrowth of Candida spp., most commonly C. albicans, which are normal inhabitants of mucosae and the GIT in many animals. Infection is usually associated with immunosuppression and/or unhygienic conditions and is most typical on oral and genital mucosal surfaces, but may extend to involve adjacent skin. Classically, there is a white to grey moist exudate associated with clumped fur, erythema and mild erosions. Cutaneous candidiasis is seen in several Aus­tralian native species, most commonly in individuals being hand-reared (Vogelnest and Woods 2008).

Diagnosis requires fungal culture. However, cytology (direct impression smears) in conjunction with consistent clinical signs are suggestive. Candida spp. typically appear as round to slightly ovoid yeast with tiny buds or may be present as pseudohypae formed by chains of yeast, or rarely as true filamentous hyphae.

Treatment is usually effective with cleansing and potentially topical antifungal preparations (e.g. nystatin, miconazole, terbinafine) or antiseptics (chlorhexidine), although systemic antifungals may be helpful for severe infections (e.g. fluconazole, itraconazole) (see Appendix 4). Nystatin cream has been used for skin lesions in macropods. Addressing predisposing factors is important (e.g. hygiene). Cleansing with water followed by chlorhex- idine (1-3% solution) is often effective in bats. Access to direct sunlight for at least 10 min bid is also helpful (Olsson and Woods 2008).

b. Dermatophytosis

Dermatophytosis is one of the more common but spo­radic skin infections occurring in a wide range of Aus­tralian mammals. It is caused by a variety of keratinophilic fungi that reside in soil (geophilic) or on other animals (zoophilic). Infective fungal spores may survive in the environment for months to years and minor skin trauma associated with suitable environmental conditions (warmth and humidity) favour infection. Lesions are most typically well-demarcated areas of alopecia, with or without peripheral erythema, papules, pustules or scaling and are most common on the extremities (face, tail, limbs). Dermatophytosis is reported in:

Fig. 12.5. Multifocal areas of well-demarcated alopecia on the hindlimbs of a red kangaroo (Osphranterrufus) with dermatophytosis. Photo: Taronga Zoo

Fig. 12.6. Asymmetrical well-demarcated alopecia in a koala (Phascolarctos cinereus) with dermatophytosis. Photo: Taronga Zoo

• Platypuses (Ornithorhynchus anatinus): Trichophyton mentagrophytes - tail alopecia (Booth and Connolly 2008)

• Macropods: T. mentagrophytes followed by Micro- sporum gypseum most commonly implicated; T. ver- rucosum and T. mentagrophytes var. nodulare also reported; infections common in zoo-housed animals (estimated prevalence of 28%) - multifocal well- demarcated circular areas of complete alopecia most frequent, large lesions (1-5 cm diameter) common, tail most frequently affected, followed by pinnae and hindlimbs (Boulton et al. 2013) (Fig. 12.5). Reported in several species and particularly common in red kanga­roos (Osphranter rufus), including recurrent outbreaks in zoo-housed animals (Vogelnest and Portas 2008; Boulton et al. 2013)

• Koalas: T. mentagrophytes and M. gypseum have been isolated from lesions on free-ranging and managed koalas - face (especially on or near the nose), ear pinnae, dorsal feet and lateral limbs most often affected; blepharitis and onychitis reported (Blanshard and Bodley 2008; Mirhendi et al. 2016) (Fig. 12.6)

• Bilbies: Trichophyton spp. isolated from one managed colony (Lynch 2008)

• Bats: dermatophyte infections (Olsson and Woods 2008; Lorch et al. 2015) can appear similar to ‘white­nose syndrome’ (see Chapter 42)

• Dingoes: M. gypseum, M. canis - classical lesions in managed animals (Hulst 2008)

• Australian sea-lions (Neophoca cinerea): M. gypseum - multifocal alopecic lesions ~1 cm diameter, mostly on the ventral body surfaces, especially axillae and flippers (Phillips et al. 1986).

Diagnosis can be achieved by direct microscopy, skin biopsies or fungal culture in conjunction with consistent clinical lesions. All techniques can have false-negative results depending on the sites sampled, timing of sam­pling and degree of host immune response. Most infec­tions spontaneously resolve within 2-3 mo, so fungal elements may be absent when samples are collected later in the course of disease, even though alopecia and ery­thema may still be prominent. With more florid inflam­matory responses, fungal elements may be sparse.

• Direct microscopy - adhesive tape impressions and/ or trichograms may provide immediate results. Most animal infections are ectothrix (infective elements remain on the outside of the hair shaft), so clearing agents (e.g. KOH) are not required. Hairs should be examined under low magnification (e.g. ?4 objective) for irregular thickened shafts that have reduced defi­nition of layering (cuticle, cortex, medulla) (Plate

12.3), which are then examined using the ?40 and ?100 objectives for fungal spores and/or hyphae (Plate

12.4). Wood’s lamp examination can help identify infected hairs for some Microsporum infections (e.g. in ~50% of M. canis), but will be negative with most other species.

• Fungal culture is required to confirm the species, but some dermatophyte species do not grow readily or saprophytic fungi may overgrow culture media. Sampling multiple clean lesions (no soil contamina­tion) via surface skin scrapings (collecting surface scale together with broken hairs) in addition to hairs plucked from the periphery of alopecia areas may improve sensitivity of results. Plucking a small number of hairs from one lesion is not optimal.

Treatment with antifungals may be considered as for domestic mammals (see Appendix 4). Many localised or mild infections will self-resolve within 2-3 mo, although with variable risks of contagion during this time. Affected animals should be isolated (with consideration to welfare implications) and steps taken to prevent transmission via fomites and to ensure that husbandry is optimal and environmental stressors are reduced.

Topical treatment is often effective, but the regular application required (e.g. once-or twice-daily for creams and lotions) is not suitable for all animals.

• Terbinafine cream 10 mg/g sid (Lamisil, GlaxoSmith­Kline Australia, Boronia, Vic.) is reported effective in koalas

• Enilconazole 1% solution (Austrazole, Ausrichter Aus­tralia, Annandale, NSW) is a leave-on rinse registered for treatment of dermatophytosis in domestic dogs and horses and safe in domestic cats if grooming is prevented until the hair coat is dry, requiring applica­tion q 3-4 d (i.e. twice weekly); it has been used effec­tively in tractable red kangaroos, sprayed onto affected areas (L Vogelnest pers. comm.)

• Antifungal shampoos (e.g. Malaseb, Dermcare Aus­tralia, Slacks Creek, Qld) may be adjunctive and help limit contagion, but have low residual action

Systemic treatments may be needed for severe infec­tions or outbreaks where topical treatment is not feasible (see Appendix 4). Reported options include:

• Itraconazole in echidnas, macropods, koalas and rodents

• Terbinafine in macropods and koalas. In little brown myotis (Myotis Iucifugus) infected with Pseudogym- noascus destructans 20-60 mg/kg SC sid for 10 d appeared safe and achieved presumed therapeutic concentrations, whereas 200 mg/kg SC sid for 5 d was associated with neurological effects and high mortal­ity rates (Court et al. 2017)

• Griseofulvin: therapy is reported in macropods, but newer antifungals are safer and more efficacious, and its use is now discouraged

Environmental treatment is an important considera­tion for animals in managed care. With outbreaks in enclo­sures, steps to reduce environmental contamination should occur concurrently with treatment of affected animals. Substrate is ideally removed and the base surface thor­oughly cleaned, disinfected and dried before new substrate placed. For solid surfaces, an initial detergent clean, fol­lowed by 0.6% bleach disinfection appears most effective. Soil surfaces are more difficult; removal of surface layers and exposure to sunlight and thorough drying should be effective if practical. Bleach can be used, but although quickly effective, is also quickly inactivated by organic material (Moriello et al. 2017). Enilconazole is available in some countries as a fogger or spray for the environment, which may be more efficacious for soil floors.

Chrysosporium keratinophilum is a keratinophilic non-dermatophyte fungus, commonly isolated from soil and generally considered non-pathogenic, but a common skin contaminant that feeds on non-living keratinous material. It was putatively associated with infection in multiple zoo-housed red-necked wallabies (N. rufogri- seus) housed in a facility in France (Pin et al. 2011). Onychomycosis was the primary presentation. The enclo­sures were cleaned and sprayed with 0.2% enilconazole solution monthly for 4 mo and no new cases occurred in the following 6 mo. Treatment with ketoconazole 15 mg/ kg PO sid for 20 wk did not improve severe cases. Derma­tophytosis in this outbreak, and incidental culture of this fungal species, is possible.

2.1.3 Bacterial diseases

Secondary superficial bacterial infections are well recog­nised in domestic species; typically associated with pus­tules, papules and variable degrees of alopecia, erythema, scaling and crusting. Causal bacteria are usually Staphy­lococcus spp. that reside on the skin surface as part of the normal varied skin microbiota, but with great potential as opportunistic pathogens. Underlying diseases (e.g. aller­gies, immunosuppression), local skin factors (e.g. minor trauma, skin folds) and suboptimal environmental condi­tions (e.g. high or low humidity) are recognised predis­posing factors. There are scarce reports of superficial bacterial skin infections in Australian mammals (see sections 2.1.10 and 2.2.2), which may represent a true rare occurrence or reflect under-recognition.

Diagnosis is most reliably achieved with surface cytol­ogy (see Table 12.2 and section 1.3.1), with the most con­sistent finding being repeatable intracellular bacterial cocci within neutrophils.

Treatment of superficial bacterial infections generally requires surface cleansing and antiseptics only. Chlo- rhexidine 2-4% solution (non-soap formulation) is suita­ble to apply and leave on intact skin surfaces and is less irritant and inactivated by organic material (crusting, exudation) compared with iodine. Silver sulfadiazine 1% cream (e.g. Flamazine®, Smith & Nephew Australia, North Ryde, NSW) is less irritant for lesions involving mucosal regions. Povidone iodine 0.5% solution is suita­ble for periocular areas. Systemic antibiotics may be required for severe infections or where topical treatment is not practical, but is generally unnecessary for superfi­cial infections that present with alopecia, erythema and scaling. Addressing the underlying primary disease or factors is important to limit recurrence.

2.1.4 Nutritional dermatoses

Nutrition is a key factor in skin health and is likely involved in a wide range of presentations of alopecia and/ or scaling. It should always be a consideration, particularly with multiple animals affected, although some individu­als may be more susceptible to hair coat changes despite the same diet. Despite this, skin disease linked to poor nutrition is rarely documented in Australian mammals. It likely plays a role in cases of hand-reared young present­ing with prominent alopecia. It may be an important factor in some presentations of unknown aetiology (e.g. ‘orthokeratotic hyperkeratosis’ of echidnas; see 2.1.8).

Patchy or symmetrical alopecia is reportedly common in bats in managed care, associated with malnutrition (protein and/or fat-soluble vitamin deficiencies) caused by inadequate dietary supplements or prolonged use of milk formula beyond normal weaning. Correction of the dietary deficiency or weaning is reported to result in res­olution of skin changes (Olsson and Woods 2008).

2.1.5 Environmental dermatoses

The environment is a key factor in skin health and can be suboptimal for both free-ranging and managed animals. Several factors have been linked with skin disease.

Substrate factors

Numbats in managed care may have inflammatory skin lesions associated with excessive moisture in the enclo­sure substrate, particularly in obese animals, with lesions including alopecia, scaling and erythema on ventral body and axillae. Secondary bacterial infections may be involved (Vitali and Monaghan 2008).

b. Stress

Bilaterally symmetrical alopecia is reportedly associated with stress in hand-reared macropods and possums, which may be extensive on the trunk, tail and limbs. Hindlimb digits may be wet and macerated from exces­sive sucking (Vogelnest and Woods 2008). Skin and hair problems are also commonly linked to stress in bilbies, including enclosure changes, social incompatibility, fre­quent handling and concurrent systemic disease. Intraspecific aggression, particularly between males, is sometimes identified as a cause of partial alopecia of the rump area and is often accompanied by small bite wounds and scratch marks (Lynch 2008).

2.1.6 Physiological changes

Regional alopecia is recognised to occur sporadically in a variety of mammals because of the physiological and physical changes associated with reproduction and normal behaviours.

• Platypus: alopecia on the tail and sometimes more widespread is reported as more common than derma­tophytosis, likely induced by biting or burrow plugging in the breeding season (Booth and Connolly 2008)

• Koalas: patchy alopecia on the backs of females carrying young after pouch emergence, with saddle­shaped areas of darker, less dense hair on the back where the young sit and sometimes circular areas on the flanks where the hindfeet clasp (Blanshard and Bodley 2008)

• Dasyurids: patchy alopecia associated with moulting during or after the breeding season; aged animals may develop progressive alopecia (Holz 2008); scaling (most notable on the dorsum) for short periods after oestrus or parturition in Tasmanian devils (L Vogel- nest pers. comm.)

• Bats: alopecia may occur associated with reproduction and transiently at times of moulting (Olsson and Woods 2008)

2.1.7 Congenital diseases

A familial form of ichthyosis was reported in two emer­gent red-necked wallabies, from different matings of the same parents, characterised by marked scaling of haired skin and foot pads and early mortality (Hazen et al. 2007).

2.1.8 Autoimmune

Pemphigus foliaceus was diagnosed histologically in one free-ranging sub-adult common brush-tailed possum, associated with a Vesicopustular and scaling dermatitis of the nailbeds (Johnson and Hemsley 2008). Skin histopa­thology is required for diagnosis and immune-suppressive treatment as for domestic mammals may be considered, although disease is often life-long in most species.

2.1.9 Neoplasia

Cutaneous epitheliotropic lymphoma of T-cell origin is reported in two zoo-housed Tasmanian devils, present­ing with generalised erythema and scaling, with regions of alopecia, erosions and crusting (Scheelings et al. 2014; see Chapter 18). Skin histopathology is required for diag­nosis. Palliative chemotherapy protocols for this disease are well reported for domestic mammals.

2.1.10 Idiopathic alopecic, erythemic and scaling dermatoses

Several idiopathic syndromes have been recognised in some Australian mammals and remain incompletely characterised. Some presentations have been named based on similar clinical and/or histopathological findings.

• Short-beaked echidna: Orthokeratotic hyperkeratosis - multiple cases are recognised in managed echidnas in multiple zoos and similar findings are reported rarely in wild echidnas. Echidnas present with varying degrees of patchy alopecia (usually hair only, but occasionally some quills), mild to moderate scaling and occasionally erythema affecting the dorsal trunk most severely and extending onto the ventrum in some animals (Fig. 12.7)

Fig. 12.7. Patchy alopecia with scaling and some broken quills in a short-beaked echidna (Tachyglossus aculeatus). Photo: Larry Vogelnest

(L Vogelnest pers. comm.). Pruritus is not apparent. Both hyperkeratosis (histological description) and scaling (clinical description) are non-specific changes with multiple potential aetiologies. Poxvirus particles have been identified in lesions in one case and bacterial folliculitis and burrowing mites in some cases (ARWH 2018). Cases became less frequent following dietary changes for echidnas in one zoo and fatty acid supple­mentation (e.g. Dermoscent Essential 6 Spot on, PAW Blackmores; oral Megaderm, Virbac Australia, Milperra, NSW) may be helpful, although cases also appear to resolve spontaneously (L Vogelnest pers. comm.). Dietary insufficiencies and/or suboptimal hus­bandry (e.g. low or high humidity), seem likely causes; however, a role for infectious agents and multifactorial causes remains possible.

• Macropods: Xeroderma - prominent scaling in hand­reared macropods may be thick and produce fissuring on the tail, elbows, hocks. Topical moisturisers have been applied regularly in a preventative role and fatty acid supplementation has also been utilised (e.g. Megaderm, Virbac Australia), but the cause of this pres­entation, and the safety and efficacy of such treatments, is currently unknown (Vogelnest and Portas 2008).

• Koalas: Volar hyperkeratosis - small numbers of managed and free-ranging koalas are described with marked scaling and fissuring of the volar surfaces of feet. Histopathology revealed papillated orthokeratosis with focal parakeratosis and focal cutaneous horns; no infectious agents were apparent (Canfield et al. 1992).

• Wombats: dry scaly skin is common in hand-reared young on milk replacers; it may respond to skin mois­turising (e.g. lanolin or sorbolene cream) and poten­tially, fatty acid supplementation.

• Dasyurids: free-ranging spotted-tailed quolls may have multifocal to coalescing, exudative and crusting lesions, particularly of the hindquarters, that appear most likely to be associated with ectoparasitic, envi­ronmental and/or social factors. Adult Tasmanian devils (free-ranging and managed) often have patchy alopecia, erythema and excoriations, and apparent pruritus, which has been associated with ectoparasites, but is also potentially associated with trauma or other unknown causes.

• Possums: Exudative dermatitis - common in free- ranging common brush-tailed possums, typically pre­senting with ulcerative facial lesions (see section 2.2.5); Rump wear - common in free-ranging common and mountain brush-tailed possums, resulting in alopecia usually restricted to the rump, but potentially extend­ing to other body regions. It is a poorly defined and characterised presentation, with some potential overlap in signs with exudative dermatitis (see below). Older possums appear more likely to be affected and a hypersensitivity to ectoparasites, particularly laelaptid mites (see section 2.1.1a) has been proposed. Alopecia may consist of varying degrees of decreased length and thickness of hairs in affected regions and although gross skin lesions are often absent, focal small crusts are reported in some cases (although are also reported in possums without alopecia) (Hufschmid et al. 2010). Rump wear is also reported in eastern ring-tailed possums in Tas. (Ringwaldt et al. 2022).

• Bilbies (managed): often have poor coat quality, with regions of mild alopecia and scaling (typically on top of the head in males and around the tail base in females). The cause is unknown, but may be multifac­torial. Stress may be an important contributory factor (see section 2.1.5b). Increased humidity in the indoor enclosure for one animal, to more closely mimic the normal cool and humid burrow microenvironment, resulted in resolution. Nutritional supplementation with fatty acids (e.g. Megaderm, Virbac; or cold- pressed sunflower oil) is reported to help but not resolve the problem.

• Pinnipeds: Alopecic syndrome - bilaterally symmetri­cal alopecia is reported sporadically in Australian fur seals (Arctocephalus pusillus) and has been evaluated in one colony where up to 50% of females, particularly juveniles, were affected. Alopecia was typically restricted to the mid-dorsum, although it extended to most of the dorsum and head in some animals. Pruritus was inapparent in most animals. Parasitic, fungal and other infectious causes were excluded, hair shaft fracture and no pathological variation to control animals was apparent on histopathology. Nutritional or toxic causes were possible, with lower levels of some minerals, and higher levels of heavy metals and pollutants, in the hair shafts of affected animals (Lynch et al. 2012).

2.2 Erosive, ulcerative and crusting dermatitis

A smaller range of differential diagnoses are important considerations for this presentation, with environmental/ husbandry causes most common, but also some impor­tant rare infectious causes. Multiple animals may be affected in both scenarios. The important steps for evalu­ation are listed.

• Historical factors: signalment, general health and development of the skin lesions (e.g. number of lesions, number of animals exposed/affected) are important and knowledge of the recognised diseases in the species is helpful.

• Husbandry: detailed review of current husbandry is essential, with knowledge of optimal husbandry for the affected species, consideration of solar exposure and likely exposure to known infectious agents.

• Physical examination: thorough physical examina­tion, including full body and close skin examination (see Table 12.1) is essential in severe or outbreak presentations.

• Skin surface sampling may be less helpful in ulcera­tive lesions, as a range of infectious contaminants are more likely with moist lesions and pathogens tend to invade the deeper dermis (see Table 12.2).

• Skin biopsies are often indicated in this presentation; it is important to sample the borders of affected areas, ensuring intact epidermis is included in samples, and to collect several samples (elliptical samples optimal; see Table 12.2).

• Further diagnostics may include systemic health screening, especially for more severe presentations, and when disseminated infections are possible.

2.2.1 Fungal diseases

Mucormycosis, caused by the environmental dimorphic fungus Mucor amphibiorum, is a major disease in free- ranging platypus in Tas., causing significant morbidity and mortality (Macgregor et al. 2010; Connolly 2015; see Chapter 28). Infection most likely occurs via skin wounds, including minor trauma from tick or larval mite attach­ment and nematode larval penetration. Infection may be subclinical in some individuals, but typically causes a severe ulcerative to nodular dermatitis, with potential invasion into SC muscle and dissemination to internal organs, especially lungs. Lesions are often prominently ulcerative, consisting of areas of complete ulceration with well-defined raised borders. Multiple lesions are often present, some coalescing. Intact alopecic nodules may also occur. Lesions are most often on the extremities (limbs, head), particularly the hindlimbs (Connolly 2015).

Diagnosis requires fungal culture; M. amphibiorum grows readily on Sabouraud’s dextrose agar at 28°C. Cytology via impression smears (from ulcers) or fine needle aspirates (from nodules) may reveal fungal spher­ules (the yeast form that occurs in tissue), but similar spherules may occur with other Mucor species. Similar lesions are reported associated with Corynebacterium ulcerans infection (Macgregor et al. 2010; Connolly 2015).

Treatment is rarely reported. Some infections may resolve spontaneously, but severe infections are fatal. One isolate of M. amphibiorum was reported sensitive to amphotericin B, but resistant to itraconazole and flucon­azole on fungal sensitivity testing. Local amphotericin treatment has been proposed as a treatment option (Con­nolly 2015).

Lacaziosis (or lobomycosis) is caused by the yeast-like organism Lacazia loboi, an uncultivable fungal species with worldwide distribution that causes chronic skin and SC infections in humans and dolphins. More recent molecular data have shown that a novel uncultivated strain of Paracoccidioidomycosis brasiliensis is the cause of dolphin lacaziosis, which has now been renamed P. ceti (Vilela et al. 2016). Disease is reported in several species of cetaceans in Australian waters. Lesions are typically multiple, firm, raised grey, white or pale-pink verrucous nodules and plaques, ranging from 1 to 30 cm (Bossart et al. 2017; see Chapter 46). Lacaziosis was reported in three Australian snub-finned dolphins (Orcaella heinsohni) with multifocal to coalescing raised pale irregular nod­ules (1-5 cm) (Grillo et al. 2015).

2.2.2 Bacterial diseases

A small number of bacteria have been associated with ulcerative and crusting skin presentations.

Corynebacterium ulcerans is a commensal that has been isolated from a range of species. Unlike most Corynebacterium spp., which are rarely pathogenic, C. ulcerans has significant pathogenic and zoonotic potential, causing skin, soft tissue, respiratory and sometimes dis­seminated infections in people, particularly if they are immunocompromised. The water rat (Hydromys chrys- ogaster) is identified as a potential reservoir of this bacte­rium (Eisenberg et al. 2015). Corynebacterium ulcerans has been associated with ulcerative skin lesions in the platypus (may mimic mucormycosis), in a Tasmanian devil (Macgregor et al. 2010) and in an outbreak in zoo-housed water rats (Eisenberg et al. 2015). Diagnosis requires bacte­rial culture, which is typically straightforward. Cytology (e.g. impression smears) and biopsies should reveal gram­positive bacterial rods and associated dermal inflammatory response. Treatment consists of antibiotics and antitoxin in humans, but is unreported in Australian mammals.

Dermatophilus congolensis is an obligate animal pathogen; however, infective zoospores can survive in crusts in the environment for months and become reacti­vated by moisture. It may cause multifocal exudative, ero­sive and crusted lesions in macropods, which may be extensive and severe in some cases. Disease (dermat- ophilosis) typically occurs in managed animals with per­sistently wet hair coats from extended exposure to rainfall or excessive environmental humidity (Vogelnest and Portas 2008). Two cases in free-ranging eastern ring-tailed possums with extensive lesions and poor body condition presented shortly after a period of prolonged rainfall (T Portas pers. comm.). Diagnosis is via cytology if character­istic branching filamentous rods, consisting of parallel rows of coccoid elements that break into infective zoo­spores (‘railroad tracks’), are present. Culture requires specialised microaerophilic conditions. Treatment with topical antiseptics (e.g. chlorhexidine 2-4% solution) and removal from the wet environment should be effective in most cases. Systemic antibiotics are rarely indicated; how­ever, long-acting oxytetracycline is reportedly effective. Thorough cleaning of the environment to remove infec­tive crusted material is indicated after outbreaks.

Erysipelothrix rhusiopathiae is found worldwide as a commensal or pathogen in a wide variety of animals and able to persist for long periods in the environment. Dis­ease has been reported in macropods, a numbat and ceta­ceans (Vaughan-Higgins et al. 2013). Red and western grey kangaroos may present with focal ulcerative lesions, which may be characteristically diamond-shaped (rhom- boidal), on the limbs and trunk, concurrently with signs of systemic illness. However, acute mortality is the most common presentation. Managed and free-ranging ceta­ceans may present with signs ranging from mild charac­teristic skin lesions (diamond-shaped areas of altered pigmentation to ulceration) to acute death. Diagnosis is often suspected with classical skin lesions and is con­firmed by anaerobic bacterial culture (growth may be slow without enrichment media). Histopathology will reveal vasculitis and gram-positive rods within vessel endothelium may be present. Treatment with penicillin is usually effective if initiated early in disease; potentiated sulfonamides or tetracyclines are alternative options. Vaccination can be protective for cetaceans, but is often not indicated as significant disease is sporadic.

Pseudomonas aeruginosa is ubiquitous in the envi­ronment in soil, water and other moist locations. It has been associated with pouch dermatitis in managed macropods presenting with a moist, greasy, malodorous pouch, which may be more likely with long-term antibiotic therapy or chronic stress (Vogelnest and Portas 2008). Epidemics of similar pouch dermatitis and poten­tial mortality have been described in koalas (pouch death syndrome), with P. aeruginosa most commonly impli­cated, but other bacteria including Klebsiella spp. and Proteus spp. and yeast (Candida albicans) sometimes cul­tured (Blanshard and Bodley 2008). Pouch infections have also been reported in common brush-tailed and eastern ring-tailed possums and may also result in mor­tality of females and/or young (Johnson and Hemsley 2008). Diagnosis requires bacterial culture in conjunc­tion with the presence of bacterial rods on cytology: either intracellular within neutrophils with active infec­tion or colonising on keratinocytes with bacterial over­growth. Isolation from the skin/pouch surface does not confirm pathogenicity (see section 1.3.1). Treatment typi­cally requires topical cleansing and antiseptics. In macro­pods and koalas, dilute chlorhexidine solution (2-3% is suitable for intact skin), followed by topical silver sulfadi­azine 1% cream is reported effective. In possums, paren­teral antibiotics are often required.

Secondary bacterial infections with commensal skin bacteria, particularly Staphylococcus spp., may produce or contribute to ulcerative lesions in domestic mammals. Evidence of intracellular bacterial cocci on impression smears from ulcerative lesions is supportive of a role in pathogenesis. Based on occurrence in domestic mam­mals, such infections are likely to occur sporadically in Australian mammals.

2.2.3 Mycobacteria ulcerans

Unlike the nodular presentations of many mycobacterial infections, M. ulcerans is a cause of ulcerative skin lesions. In koalas, M. ulcerans infection is associated with single or multiple ulcers, 0.5-2 cm with a moist grey base, most commonly on the volar surface of the foot pads of mature males, and also reported on the limbs, face, rump and scrotum (Blanshard and Bodley 2008). In possums, 1-2 focal areas of ulceration with overlying crusting are most typical on the extremities, sometimes with oedematous swelling. Infection appears more often multifocal and in some cases disseminated in eastern ring-tailed possums (see Chapter 38). Minor self-limiting infection is reported in one common brush-tailed possum and one mountain brush-tailed possum (O’Brien et al. 2014). Infection is also reported in dasyurids, including spotted-tailed quolls, Tasmanian devils and a long-footed potoroo (Potorous longipes) (Holz 2008; Vogelnest and Portas 2008). Diagnosis requires direct smear examination for acid fast bacilli (AFB), culture for M. ulcerans, PCR and histopathology. Histologically, abundant acid-fast myco­bacteria are usually evident within macrophages and extracellularly. PCR is the most rapid, sensitive and spe­cific method for the diagnosis of M. ulcerans disease (WHA 2024). Treatment is ideally surgically excision if feasible; alternatively, protracted courses of antimicrobi­als as for domestic dogs and cats may be considered. See Chapters 22, 37 and 38 for more detail on mycobacterial infections.

2.2.4 Viral diseases

Outbreaks of acute mortality associated with herpesvirus infection are reported in a wide range of macropods, pri­marily managed animals, including bettongs, quokkas, pademelons (Thylogale spp.), wallabies and kangaroos (see Chapter 23). Skin lesions associated with systemic signs are reported in quokkas and parma wallabies (N. parma), consisting of erythema, vesicles and ulceration of facial, oral and anogenital areas. Herpesvirus infections may similarly present with either life-threatening dis­seminated infection or skin lesions in cetaceans, includ­ing dusky dolphins (Lagenorhynchus cruciger) and Indo-Pacific bottle-nosed dolphins (Tursiops aduncus). Infections are usually reported in juvenile animals and several alphaherpesviruses, unique to dolphins, have been identified. Lesions consist of myriad papules and small plaques that progress to grey erosions, affecting widespread areas including the dorsolateral trunk, head, dorsal fin and flukes (Manire et al. 2006; Bossart et al. 2015). Herpesvirus infections have also been confirmed concurrently with papillomaviruses in proliferative lesions in dolphins (see section 2.3.5). There are no reports of herpesvirus skin disease in cetaceans in Aus­tralia. Diagnosis is reliant on viral culture or PCR testing and supported by a rising antibody titre. Intranuclear inclusion bodies on histopathology, in conjunction with consistent clinical findings, may be suggestive. Treat­ment is not reported.

2.2.5 Environmental diseases

Skin abrasions and wounds associated with trauma are recognised commonly in several Australian mammals, both free-ranging and those in managed care. These may be associated with bites, scratches or rakes (teeth or tusks in marine species) from conspecifics (e.g. during breed­ing) or other species; telemetry devices (collars, anklets) and tags; stereotypies and repeated attempts at escape from enclosures; anthropogenic debris (fishing gear, plastic rings); burns (bushfires, direct contact with stovetops, fire places in camping areas and in summer from hot roofs and bitumen); sustained during capture and restraint procedures (e.g. tail degloving in rodents); and vehicle strike (motor vehicles, boats). In managed care, good husbandry and management are important for prevention. Routine wound care and correction of under­lying factors are important to resolution. In bats, necrosis and sloughing of pinnae or wing membranes occurs from trauma (e.g. pups sucking on each other), as the vascular supply is easily disrupted. A survey of skin lesions in managed bats in Europe, North America and Australasia revealed that crusting, swelling, erythema and necrosis affecting pinnae (32%) and wing membranes (29%) occurred most frequently (Fountain et al. 2017). Thermal burns from heating pads and skin irritation from urine or faecal scalding (initially apparent as bleaching of fur) are also recognised (Olsson and Woods 2008).

Photosensitisation is a potential cause of ulcerative and crusting skin lesions. Hepatotoxicity producing sec­ondary photosensitisation is documented in red kanga­roos after ingestion of Lantana camara (erosions and crusting on the muzzle, pinnae and periocular regions) (Johnson and Jensen 1998) and in eastern grey kangaroos after ingestion of Panicum gilvum (subtle skin lesions on gross examination despite severe necrotising dermatitis histologically) (Steventon et al. 2018).

Free-ranging southern hairy-nosed wombats have been reported with extensive patchy to diffuse alopecia on the dorsolateral trunk and head and poor body con­dition, with suspected pyrrolizidine alkaloid hepato- toxicosis (see Plate 19.1 and Chapter 19) (Woolford et al. 2014).

2.2.6 Neoplasia

Squamous cell carcinoma and other dermal neoplasia is covered in Chapter 18. Squamous cell carcinoma is the most common cutaneous neoplasm reported in marsupi­als. Typical clinical lesions range from regions of ery­thema with erosion and ulceration to skin nodules. Diagnosis is by histopathology.

2.2.7 Idiopathic ulcerative dermatoses

Several presentations of ulcerative skin disease of unknown aetiology are recognised in some Australian mammals.

Fig. 12.8. Severe facial ulceration and scarring in a common brush-tailed possum (Trichosurus vulpecula) of idiopathic cause, commonly referred to as 'exudative dermatitis'. Photo: Taronga Zoo

• Common brush-tailed possum: Exudative dermatitis is common in free-ranging animals, varying from mild alopecia and excoriations to more extensive exudation, crusting and severe ulceration. Lesions most typically occur on the face (especially periocular, pinnae, lip commissures) and also on the distal limbs, neck and rump (Fig. 12.8). Eyelid swelling and conjunctivitis may occur and severe cases may be fatal. A multifacto­rial origin is proposed, with social and/or environmen­tal stresses suggested as important, compounded by a variety of infectious agents including ectoparasites, bacteria and fungi. Disease appears more common in dispersing sub-adult males and sometimes occurs con­currently with systemic diseases. Trichosurolaelaps crassipes mites have been found in some cases, but may also be present in possums without any skin disease (see section 2.1.1a). Secondary bacterial infections appear to be common, with multiple bacterial species cultured from affected skin including Staphylococcus, Streptococcus, Corynebacteria and Pseudomonas spp. (Johnson and Hemsley 2008; Pollock and Gay 2012). However, culture of microbes from the skin surface does not confirm any pathogenic role as they may simply reflect normal commensals or transient con­taminants. Prognosis with treatment in mild cases is usually good. Prognosis is poorer for distal lesions of limbs (scarring and restricted movement) and guarded for extensive and/or deep lesions. If social and/or envi­ronmental stressors are thought to be contributing factors in individual cases, careful consideration must be given to the welfare implications of releasing these animals back into habitats where these factors persist (e.g. the release of young dispersing males back into crowded habitats). Euthanasia is preferable in these cases (L Vogelnest pers. comm.). A range of oral or injectable antibiotics with or without antiseptic washes are effective in mild cases. Oral cefaclor is well accepted, with apparently good efficacy in cases deemed suitable for treatment (T Portas pers. comm.). Secondary yeast infections may be associated with greasy rather than moist exudative lesions, which respond to antifungal (oral fluconazole and topical antifungal therapy) rather than antibiotic therapy (T Portas pers. comm.).

• Eastern ring-tailed possum: ^cSwollen paw syndrome is common in the Sydney region of NSW, presenting as swelling, moist ulceration and eventual necrosis of distal ends of limbs and sometimes the dorsal nose, pinnae or tail. A variety of potential causes have been proposed, including photosensitisation, thermal injuries, electrocution, bacterial or viral infections and fungal or plant toxicities (Johnson and Hemsley 2008).

• Greater bilby: Ulceration of plantar tarsal areas is rec­ognised in some managed individuals and may also involve the tail. Excessive moisture in the enclosure substrate may predispose and more frequent changing and/or cleaning of substrates appears to reduce inci­dence. Secondary infections with Staphylococcus spp. bacteria may contribute (Lynch 2008).

2.3 Nodules and nodular swelling

Nodular skin presentations are often less diagnostically challenging than other presentations, as skin biopsies for histopathology are often diagnostic, with infectious and neoplastic causes the most common. Any animal present­ing with nodular skin disease, and particularly with mul­tiple lesions, has potential for systemic involvement. Important steps for evaluation are listed.

• Historical factors: signalment, general health and development of the skin lesions (e.g. number of lesions, number of animals exposed/affected) are always important and knowledge of the recognised diseases in that species is helpful.

• Husbandry: review of current husbandry may be helpful, particularly any likely exposure to known infectious agents.

• Physical examination: thorough physical examination, including ocular and oropharyngeal examination, is important to screen for evidence of disease at other sites.

• Skin cytology: fine needle aspiration may yield a diag­nosis or narrow the diagnostic possibilities. Multiple samples from a range of lesions will maximise value, sampling more peripherally in large lesions to avoid central areas of necrosis and from any intact areas containing exudate. Needle fenestration (reposition­ing the needle tip multiple times within a mass) might provide higher yield for some nodules. Sampling via swabs or impression smears provides less useful infor­mation, because of the non-specific inflammation and contaminate microbes. Granulomatous or pyogranu- lomatous inflammation is common with most of the infectious differential diagnoses but may complicate some neoplastic lesions. Some infectious organisms may be very sparse and/or require special stains to visualise (e.g. Mycobacteria, Nocardia and Cryptococ­cus spp.). Sterile inflammatory causes are recognised in domestic mammals and humans.

• Skin biopsies are often indicated in this presentation (see Table 12.2). It is ideal to sample multiple lesions when present to aid identification of infectious agents if organisms are sparse, or more reliable exclusion of infectious agents for sterile causes. Larger nodules should be sectioned before placing in formalin to enable sufficient fixation throughout the sample. Samples can also be frozen for PCR testing.

• Microbial culture: fine needle aspiration samples and tissue biopsies (collected by sterile technique) may be important for microbial culture to confirm causal infectious agents (see section 1.3.1).

• Further diagnostics may include systemic health screening, especially with multiple nodules or animals affected, and when disseminated infections are possible.

2.3.1 Parasitic diseases

Demodex mites may produce nodular lesions in some animals rather than the more typical alopecic and scaling presentations (see section 2.1.1a). Nodular demodicosis is recognised in multiple dasyurids, including agile ante­chinus, dibblers, greater hairy-footed dunnarts, kalutas and spotted-tailed quolls. Small numbers of discrete nod­ules are characteristic, most commonly on the limbs, head, tail base and genital areas in antechinus, on the feet and trunk in quolls and on the face in dibblers (Holz 2008). Treatment has included surgical excision and topi­cal ivermectin on nodules in dibblers; however, recur­rence and incomplete resolution are reported (Holz 2008). Sustained treatment as for more typical follicular infec­tions may be more effective (see section 2.1.1a).

Nematodes are a sporadic cause of skin nodules, asso­ciated with larval migration through skin. Larval stages of the python nematode (Ophidascaris robertsi) have been associated with nodules in multiple dasyurids (brown antechinus, dusky antechinus [A. antechinus], brush­tailed phascogale [Phascogale tapoatafa] and quolls) and bandicoots (northern brown, long-nosed) (Holz 2008; Lynch 2008). A bat nematode (Riouxgolvania beveridgei) has been associated with skin nodules in southern bent­winged bats (Miniopterus orianae bassanii) and eastern bent-winged bats (M. orianae oceanensis). White papules (1-2 mm), some with central small crusts, were reported on non-furred areas, typically on limbs, sometimes with adjacent small ulcers and excoriations (McLelland et al. 2013). Effective treatment is not reported.

Cestodes may also cause nodular dermatitis. Larval stages (plerocercoids) of Spirometra erinacei cause large SC nodules (sparganosis) in free-ranging short-beaked echidnas in Vic., SA and NSW (Middleton 2008; see Chapter 29). Sparganosis is also reported in numerous dasyurid species, bandicoots and water rats (Breed and Eden 2008; Holz 2008; Lynch 2008). Larval stages of the canid cestode, Taenia serialis, may cause SC nodules (coenuriasis) in eastern ring-tailed possums (Johnson and Hemsley 2008). Surgical excision of cestode lesions may be curative in early cases. However, debulking and anthelmintic treatment (e.g. praziquantel) may be needed for large lesions.

2.3.2 Fungal diseases

Cryptococcosis is a common disease in free-ranging and managed koalas and may be associated with nodular or crusting skin lesions (see Chapter 25). Skin lesions were reported in 3 of 43 cases, with restriction to localised skin lesions in 2 cases (Krockenberger et al. 2003).

2.3.3 Bacterial diseases

Bacterial pseudomycetoma (also called botryomycosis) is caused by bacterial infection, most typically with Staphylococcus spp., in localised walled-off, deep dermal foci that mimic deep saprophytic fungal infections. Lesions are typically solitary on the extremities and occur in multiple species. Rare cases in the short-beaked echidna are reported (Middleton 2008; Doneley and Sprohnle-Barrera 2021). Surgical excision may be opti­mal, as antibiotic penetration to lesions can be difficult, and was curative in an eastern bettong with a localised lesion (T Portas pers. comm.). However, lengthy antibiotic courses may be effective.

Nocardiosis is caused by infection with Nocardia spp. (N. asteroids, N. brasiliensis or N. transvalensis), which are ubiquitous bacteria found in soil in many regions of the world. Infections may be localised in skin, bone, lungs or liver, or be disseminated. Macropods are reported with internal infections or with SC abscesses (Vogelnest and Portas 2008). Cetaceans, most com­monly stranded juveniles, may present with internal infections or skin lesions: typically, solitary nodular lesions with or without draining tracts (Blyde and Vogelnest 2008).

Streptobacillus moniliformis is reported to infect managed spinifex hopping mice (Notomys alexis) and free-ranging house mice (Mus msuculus) from south­eastern Qld. This bacterium is the cause of rat-bite fever in humans, with transmission primarily via bite wounds. It is a commensal in the nasopharynx of the brown rat and may be endemic in free-ranging house mice. It may result in disease at high population densities and during times of stress (e.g. mouse plagues). It can present with SC abscesses, single or multiple swollen joints, or signs of systemic illness (Breed and Eden 2008).

Streptococcus phocae was associated with multiple skin nodules (3-8 cm firm, raised, occasionally ulcer­ated) in the tail fluke and disseminated infection in one short-beaked common dolphin (Delphinus delphis) with concurrent morbillivirus infection. Skin histopathology revealed pyogranulomatous dermatitis and panniculitis, with leucocytoclastic vasculitis, with intralesional and IV gram-positive cocci. A cutaneous route of entry for dis­seminated infection was considered likely. Streptococcus spp. are commensals and among the most commonly reported pathogens in cetaceans (and also in pinnipeds) (Diaz-Delgado et al. 2017).

2.3.4 Mycobacterial diseases (see Chapter 22)

Skin infection typically presents as discrete nodules, or regions of nodular swelling with draining tracts, with organisms usually implanted via skin wounds. Ulcerative presentations occur less commonly (see section 2.2.3). Non-tuberculous mycobacterial skin infections include:

• rapidly growing species (e.g. M. chitae, M. fortuitum, M. smegmatis, M. chelonae), which have been reported in quokkas, dasyurids and numbats. In spotted-tailed quolls and Tasmanian devils the lesions include firm plaques, nodules and nodular regions with draining tracts, most commonly on the dorsal neck, trunk and axillae, and often linked to bite wounds associated with breeding (Reppas et al. 2010). The M. fortuitum complex is associated with significant disease in Tas­manian devils (see Chapters 22 and 38).

• the M. avium complex (e.g. M. intracellulare, M. avium), which may cause more extensive infections and has been reported in managed bettongs, potoroos, quokka, tree-kangaroos, wallabies and kangaroos, most often systemic. Reports of skin lesions include: rufous bettongs with SC nodular lesion (abscess caused by M. avium), free-ranging long-footed potoroos with nodules and ulceration (M. avium) (Vogelnest and Portas 2008; Michael and Sangster 2010) and numbats with pododermatitis and ventral pustular dermatitis (Michael and Sangster 2010).

Treatment in multiple dasyurids has been unsuccess­ful with surgical debulking and lengthy oral antimicrobi­als including amikacin, enrofloxacin and rifabutin (Holz 2008). Rapidly growing mycobacteria can be readily cul­tured and susceptibility testing can guide the selection of more likely efficacious agents, although treatment courses of 6-12 mo are often required for effective treatment. Treatment of a Tasmanian devil with panniculitis caused by M. mageritense, with in vitro susceptibility to doxycy­cline and moxifloxacin, was successful following initial doxycycline and then moxifloxacin therapy (Reppas et al. 2010). Treatment for M. fortuitum complex infections in Tasmanian devils is described in Chapter 22.

2.3.5 Viral diseases

Poxvirus infection is reported in a wide range of animals, with some species restricted to a narrow host range and others with cross-species and sometimes zoonotic poten­tial (e.g. cowpox).

• Short-beaked echidna: one report (Ladds 2009).

• Macropods: numerous reports in juvenile and sub­adults, including quokkas, common wallaroos, Tasma­nian pademelons (T. billardierii), wallabies (agile, swamp, tammar) and kangaroos (red, eastern grey, western grey) (Vogelnest and Portas 2008). Novel pox­viruses have been isolated and sequenced from free- ranging eastern grey (EKPV) and western grey kangaroos (WKPV) (Bennett et al. 2017; Sarker et al. 2017). Lesions are most common on extremities (face, feet, tail), consisting of single to multiple papules to nodules (a few millimetres to 5 cm) with an irregular surface and often a small central umbiliform crater (Vogelnest et al. 2012; Bennett et al. 2017) (see Chapter 31, Fig. 31.2). Lesions have sometimes confusingly been referred to as ‘papillomatous’; however, there is no asso­ciation with papillomavirus. Lesions have been likened to those produced by human Molluscum contagiosum infection, which is a related but different poxvirus (Sarker et al. 2017). On histopathology, large cytoplas­mic inclusion bodies characteristic of poxvirus infec­tion may be apparent within some keratinocytes. Transmission is likely to be by direct contact or possibly through insect vectors. Lesions usually resolve over several months without treatment; surgical excision or debulking may be helpful for larger lesions affecting mobility or vision (Bennett et al. 2017).

• Possums: an outbreak is reported in a group of zoo­housed eastern ring-tailed possums, with multiple papular lesions (2-4 mm diameter) on the digits and tail, and one report in a common brush-tailed possum (Vogelnest et al. 2012).

• Bats: one report in a little red flying-fox (Pteropus scapulatus) of multiple, well-circumscribed papules (≤0.5 cm) and crusts on the wing membranes (O’Dea et al. 2016). Poxvirus was also identified in nodular nematode lesions in one southern bent-winged bat (McLelland et al. 2013)

• Cetaceans: infections common in managed and free- ranging dolphins, including the Indo-Pacific bottle­nosed dolphin; lesions are typically multifocal to coalescing circular areas (0.3-1 cm) of altered pigmen­tation (grey, black or yellow) that may have a central crater (‘pinhole’ lesions) or occasionally a black punc- tiform stippled pattern (‘tattoo’ lesions). Infections may be more common in stressed animals (Fury and Reif 2012; Bossart et al. 2017).

Papillomaviruses are ubiquitous and predominantly host species-specific, often with multiple papillomavirus species for each host. Unique papillomavirus species have been found in healthy skin of echidnas, eastern grey kan­garoos and koalas (Antonsson and McMillan 2006). Clas­sical lesions are single to multiple papules to small nodules, sometimes with an irregular surface, also referred to as ‘papillomatous’.

• Koalas: facial lesions (periocular and perioral) in young animals (Blanshard and Bodley 2008)

• Eastern quolls, Tasmanian devil (Canfield et al. 1990)

• Long-nosed potoroo ((P. tridactylus) and brush-tailed bettong (see Chapter 31, Fig. 31.1)

• Western barred bandicoots (P. bougainville): multicen­tric proliferative papules and nodules in managed and free-ranging animals, typically on the face, feet and pouch, confirmed as caused by bandicoot papilloma­tosis carcinomatosis virus type 1 (BPCV1), which is the founding member of a new group of viruses that share properties with polyomaviruses and papilloma­viruses (Chen et al. 2011) (see Chapter 41 and Fig. 41.2). Lesions begin as focal alopecia and erythema and progressively increase in size and number (Woolford et al. 2008). Larger lesions may undergo malignant transformation to squamous cell carcinoma (Munday and Kiupel 2010) (see Chapter 18).

• Common brush-tailed possum: typical papillomatous, discrete 4-10 mm circles and 1-3 cm plaques on ventral tail, confirmed as caused by a unique papillo­mavirus (Perrott et al. 2000; Reiss et al. 2015).

• Cetaceans: nodular papillomavirus lesions are reported on genital and oral mucosae of managed and free- ranging dolphins and other cetaceans, and occasional transformation to squamous cell carcinoma is reported (Bossart et al. 2017). Concurrent herpesvirus and pap­illomavirus infection has been confirmed in lesions in free-ranging Indo-Pacific bottle-nosed dolphins in Cuba (Cruz et al. 2014). However, the relative role of each virus in lesion pathogenesis is unclear.

2.3.6 Protozoal diseases

Cutaneous leishmaniasis is reported sporadically in macropods in the NT, associated with a unique Leishmania sp. Although the organism is likely endemic to the tropical region of the NT, and other Leishmania spp. cause signifi­cant morbidity and mortality in humans and other animals in other endemic regions, to date macropods are the only mammals confirmed to acquire leishmaniasis in Australia and disease reports are rare. Midges have been incrimi­nated as potential vectors (Dougall et al. 2009), but a natu­ral reservoir host remains unknown. Disease was first reported in zoo-housed red kangaroos, restricted to the Darwin region of the NT, housed in two facilities more than 20 km apart. More recently, cases have been con­firmed in zoo-housed common wallaroos, one black wal­laroo (M. bernardus) and two juvenile agile wallabies housed in separate enclosures in one facility in the same geographical region. Skin lesions consist of sparse 0.5-2 cm diameter papules to nodules, some ulcerated and crusted, most frequently on the tail, pinnae, inner forelimbs and inner hindlimbs (Dougall et al. 2009). Diagnosis requires histopathology, with amastigotes (sparse to abundant) evi­dent within macrophages within a mononuclear and gran­ulomatous nodular dermatitis. Most cases were positive for anti-Leishmania antibodies on serum ELISA testing and for Leishmania spp. on microbial culture and PCR testing of lesional tissue (Dougall et al. 2009). Treatment has not been described. Lesions in juvenile agile wallabies resolved spontaneously. Disease remained chronic in other macro­pod species, which, unlike the agile wallabies, were housed outside of their normal drier geographical ranges.

2.3.7 Neoplasia

A variety of skin neoplasms are reported sporadically in many Australian mammals (see Chapter 18). Dasyurids have a notable incidence, with multiple neoplasms reported in aged zoo-housed animals, and survival of the Tasmanian devil in the wild is threatened by an unusual transmissible tumour (Pye et al. 2016). Reported nodular skin neoplasia includes:

• Devil facial tumour disease - a transmissible, highly malignant, poorly differentiated sarcoma causing 100% mortality (see Chapter 40)

• Sporadic malignant tumours reported include:

• Cutaneous lymphoma: Tasmanian devil, sugar glider (P. breviceps), southern brown bandicoot, northern brown bandicoot (Canfield et al. 1990); epitheliotropic lymphoma in Tasmanian devil (see section 2.1.9)

• Fibrosarcoma: western quoll (D. geoffroii), fat-tailed dunnart, southern brown bandicoot (Canfield et al. 1990)

• Haemangiosarcoma: dasyurids, sugar gliders (Holz 2008: Johnson and Hemsley 2008)

• Malignant melanoma: spinifex hopping-mouse (Old and Price 2016)

• Perianal adenocarcinoma: dasyurids (Rivas et al. 2014)

• Squamous cell carcinoma: most typically, ulcera­tive presentations (see section 2.2.6)

• Sporadic benign tumours reported include:

• Haemangioma and hepatoma: dasyurids (Holz 2008)

• Histiocytoma, fibroma and melanoma: sugar gliders (Rivas et al. 2014)

• Keratoacanthoma: Tasmanian devil (Canfield et al. 1990)

• Trichoepithelioma: brown antechinus, eastern quoll, kowari, Tasmanian devils, eastern grey kangaroo, western grey kangaroos (Canfield et al. 1990; Holz 2008; Vogelnest and Portas 2008)

2.4 Pruritus

Pruritus may occur in association with prominent skin lesions in several dermatoses reported in Australian mammals, particularly with some ectoparasites (see sec­tion 2.1.1). Unlike domestic mammals and humans, in which skin hypersensitivities are very common, pruritus as a prominent finding in the absence of notable skin lesions, or in association with self-trauma lesions only, appears to be a relatively rare presentation in Australian mammals. Presentations in Australian mammals that may be caused by hypersensitivity responses include:

• Wombats (hand-reared): acute onset of regional swelling and urticarial lesions are presumed acute allergic reactions to unknown substances. Antihista­mine therapy has been utilised (Bryant and Reiss 2008).

• Bats: managed animals with acute bilateral facial swelling and conjunctivitis, pruritus and respiratory distress are reported (Olsson and Woods 2008). Presumed atopic dermatitis, responsive to cyclosporin therapy, is also reported in a Malayan flying-fox (P. vampyrus) presenting with recurrent conjunctivitis and pruritus with alopecia and moist dermatitis of the head and neck (Goodnight 2015).

• Dingoes: caudal trunk pruritus consistent with flea bite hypersensitivity is recognised sporadically in managed animals, presenting as in domestic dogs (Hulst 2008). Muzzle pruritus and dermatitis is also recognised in zoo-housed dingoes, proposed as a hypersensitivity to mosquito bites. Muzzle lesions include alopecia, erythema and focal excoriations and crusting. There are anecdotal reports of a similar pres­entation rarely in domestic dogs, but no published cases.

• Pinnipeds: wheals, patchy alopecia, miliary papules and positive reactions on intradermal allergen testing are presumed allergic reactions (Barnes et al. 2008).

2.5 Otitis externa/media

Otitis externa and/or media may be caused by primary infections (ear mites), hypersensitivities or other causes of compromised systemic and/or localised epithelial health. Secondary infections with a range of commensal and opportunistic bacteria and yeasts often complicate disease. Otitis is reported sporadically in:

• Koalas: purulent otitis externa associated with bacteria (Pseudomonas spp., Proteus spp., Escherichia coli) and yeasts isolated on microbial culture (see Chapter 33). Some infections may after pinnal wounds in fighting males (Blanshard and Bodley 2008).

• Dasyurids, gliders and possums: severe head tilt and meningitis in dunnarts, quolls, gliders (squirrel [P. norfolcensis], sugar, yellow-bellied) and eastern ring­tailed possum, most commonly associated with Pseu­domonas aeruginosa (Holz 2008; Johnson and Hemsley 2008); purulent otitis externa associated with P. aer­uginosa in an aged agile antechinus (Holz 2008).

• Bats: head tilt, ear scratching, asymmetry and altered balance associated with ear infections (Olsson and Woods 2008).

Cytology is important to accurately assess the role for secondary bacteria or yeast in otic infections, as culture alone may simply reflect normal commensals without any pathogenic role. Treatment principles are as for domestic mammals. Consideration of underlying pri­mary factors is important when secondary infections are identified.