DISEASES

4.1 Infectious diseases

4.1.1 Viral diseases

A syndrome characterised by multicentric proliferative lesions involving the skin and mucosal surfaces is seen in managed and free-ranging western barred bandicoots

Fig.

(see Chapters 12 and 18). Skin lesions first manifest as hair loss, progressing to skin erythema, thickening and the formation of nodular growths. The nodules can be situated anywhere on the body, but are commonly seen around the face, feet and pouch (Fig. 41.2). They can be extremely debilitating when around the eyes and feet, and for managed animals euthanasia is often indicated. The syndrome is strongly associated with the presence of ban­dicoot papillomatous carcinomatosis virus type 1 (BPCV1) (Woolford et al. 2008). Molecular studies sug­gest that the virus has been present in the western barred bandicoot population for at least 10 million yr (Bennett et al. 2008a; Bennett et al. 2008b). It has not been deter­mined whether the BPCV1-associated syndrome has emerged in the past 20 yr or if the syndrome was just not recognised historically. Reduced genetic diversity, co­infection with other agents and environmental changes are some factors being considered as possibly contribut­ing to an apparent increase in this syndrome’s prevalence (Woolford et al. 2009). A BPCV type 2 virus has been characterised from skin lesions found on a free-ranging southern brown bandicoot (I. obesulus) from WA (Ben­nett et al. 2008b). The prevalence of the virus and lesions in this species has not been determined.

An alphaherpesvirus infection was associated with severe respiratory disease that caused 100% mortality in a managed colony of nine bilbies in WA (Besier et al.

Fig. 41.2. Ventral abdomen of a western barred bandicoot (Perameles bougainville) with irregular papillomatous thickening of the dorsal skin of the digits and a large exophytic papillomatous mass arising from the skin of the pouch lip on the left side. (Image reproduced with permission from Woolford et al. (2008) Cutaneous papillomatosis and carcinomatosis in the western barred bandicoot (Perameles bougainville). Veterinary Pathology 45, 95-103).

2016) (see Chapter 23). Acute hepatic necrosis and inclu­sion bodies typical of herpesvirus have been noted in another zoo-housed bilby (ARWH 2018 case no. 88/2384) and a southern brown bandicoot (Melbourne Zoo case no. MZ818). In both cases the liver pathology was judged to have caused the death of the animal. A herpesvirus, peramelid herpesvirus 1, was isolated from a clinically healthy southern brown bandicoot (Stalder et al. 2015). The same virus was isolated from a swab of a tongue ulcer in an eastern barred bandicoot (P. gunnii), although the lesion was attributed to heavy nematode parasitism of this organ rather than the presence of virus. A gamma­herpesvirus was detected in 18/55 wild northern brown bandicoots from south-east Qld but clinical manifesta­tions of potential disease were not determined (Lang­horne et al. 2021). Similarly no clinical disease significance was established in a hepacivirus strain (Family Flaviviridae) found in long-nosed bandicoots (Porter et al. 2020).

4.1.2 Bacterial diseases

Coxiella burnetti, the causative agent of Q fever, has been demonstrated in the faeces of free-ranging western barred bandicoots and in ticks collected from this population (Bennett et al. 2011). In 3 of 35 bandicoots there were also antibodies against C. burnetti. Early studies into Q fever in Australia also identified the northern brown bandicoot as a likely host of C. burnetti (Derrick and Smith 1940). Molecular studies of flea-derived Bartonella spp.

4.1.3 Fungal diseases

Pulmonary and disseminated infections with Cryptococ­cus spp. have been observed in zoo-housed bilbies and eastern barred bandicoots (ARWH 2018 case nos 2408/95, 5515/1, 5616/2 and Melbourne Zoo case no. A30544) (see Chapter 25). Animals showing gradual weight loss and a pulmonary presentation were characterised by multifocal abscesses containing large numbers of Cryptococcus sp. yeasts, either C. gatti or C. neoformans. A well-circum­scribed focal lesion in the renal medulla of an eastern barred bandicoot was found to contain large numbers of yeast organisms identified as Cryptococcus sp. (Melbourne Zoo case no. 961022). The lesion was associated with mild inflammation and no other foci of yeast infection were found. A disseminated infection with a saprophytic fungus has been observed in a bilby (Murdoch University, School of Veterinary and Life Sciences case no. 15/0032). It is presumed that infection was initially via a skin wound and that the animal may have been immune-compro- mised, thus enabling dissemination of infection.

4.1.4 Parasites

The most significant protozoal pathogen of bandicoots and bilbies is Toxoplasma gondii (see Chapter 21). Clinical signs of toxoplasmosis in bandicoots before death include uncharacteristic docility, apparent blindness, incoordina­tion and a loss of ability to seek refuge. Protozoal para­sites from the genus Sarcocystis have been seen in eastern barred bandicoots, western barred bandicoots, southern long-nosed bandicoots (P. nasuta) and bilbies (ARWH 2018).

Infection of renal tissue with the coccidian parasite Klossiella quimrensis is a common incidental necropsy finding in bandicoots and bilbies (ARWH 2018). In a survey of 20 western barred bandicoots, infection was found in 6 individuals and was associated with mild, interstitial nephritis (Bennett et al. 2007). Parasitism of the bandicoot intestine and caecum by coccidial protozoa of the genus Eimeria is very common (Bennett and Hobbs 2011; Hillman et al. 2016b), but is rarely associated with significant pathology and therefore positive animals are not usually treated. However, in the occasional bandicoot, usually young animals, infection with Eimeria spp. is associated with mucosal inflammation and diarrhoea.

Giardia duodenalis has been found in the scats of free- ranging eastern barred bandicoots and southern brown bandicoots in Tas. (Bettiol et al. 1998). Surveys of free- ranging WA mammals found no Giardia spp. in western barred bandicoots, but variable prevalence in southern brown bandicoot populations, ranging from <5% to 42.3% (Hillman et al. 2016a; Hillman et al. 2017). These animals were shown to have a novel genotype (G. per- amelis) as well as G. duodenalis and G. canis. The signifi­cance of Giardia infection in bandicoots is largely unknown, although in compromised managed animals disease is possible (ARWH 2018). In southern brown and long-nosed bandicoot populations from the Sydney area, 12.2% of animals were found to be shedding Crypto­sporidium oocysts (Dowle et al. 2013). Both C. parvum (a zoonosis) and C. hominis, the human-specific form were detected. It was unclear whether the bandicoots were passively passaging the C. pavum or whether they were truly infected. Cryptosporidium oocysts were more prevalent in southern brown bandicoots from WA urban areas (21.1%) compared with bushland populations (13.0%) (Hillman et al. 2017). The oocysts were morpho­logically distinct from the typical appearance of C.

Heavy flea and/or tick burdens are occasionally seen in both managed and free-ranging bandicoots and in some cases this can result in severe debilitation. The extent of parasitism is influenced by environmental con­ditions favourable to the parasite, animal densities and individual animal health. Ticks act as vectors for microfi- larial parasites in bandicoots. The filarioid worm, Cerco- pithifilaria johnstoni has been found in eastern barred, southern long-nosed, southern brown and northern brown bandicoots (Spratt 1990). Although the microfi­laria typically accumulate in the small lymphatic vessels of the skin, occasionally dissemination of microfilaria causes severe multi-organ granulomatous disease (Mel­bourne Zoo case no. B30305). Bandicoots are a host for the paralysis tick, Ixodes holocyclus (Lydecker et al. 2015), and are generally thought to be immune to the effects of its toxin. However, in occasional animals, heavy paralysis tick infestations may have adverse effects on the health of the animal, particularly juveniles (Gemmell et al. 1991). Bandicoots and the bilby also host several mite species that occasionally have been associated with dermatitis and partial alopecia (Melbourne Zoo case no. 910320). Sarcoptes scabiei associated with generalised alopecia and thickened and cracked, exudative skin lesions has been noted in southern brown bandicoots (Healesville Sanctu­ary case no. 92/0593; Wicks et al. 2007). Southern brown bandicoots from WA have also found to host biting lice (Boopia bettongia) and a sub-adult male had the larva of the blowflies (Lucilia sp. and Calliphora sp.) present in a SC lesion (Hillman et al. 2017).

Eggs from intestinal Capillaria spp. are a common finding in faecal examinations from eastern barred and southern long-nosed bandicoots. These parasites also migrate through the lungs and encyst in the lips, tongue and oesophagus. They are very difficult to eliminate with anthelmintics and are generally considered non-patho- genic, though animals with heavy burdens occasionally show significant enteritis.

Chronic, multifocal pneumonia associated with migrating parasites is not uncommon in animals heav­ily burdened with Physaloptera peramelis, a spiruroid parasite found in the stomach of most bandicoot spe­cies. The nematode parasite, Angiostrongylus cantonen- sis has been observed in a zoo-housed bilby (ARWH 2018, case no. 4686/1). The animal presented with neu­rological dysfunction and the parasite was found in the brain, associated with severe haemorrhage and inflammation.

4.2 Non-infectious disease

Maceration and inflammation of the plantar aspect of the feet is occasionally observed in eastern barred bandicoots in managed care. Affected animals developed deeply fis­sured foot pads and secondary infections. The lesions typically occur during winter and appear to be a result of overly moist enclosure substrates.

Cholelithiasis has been observed in three eastern barred bandicoots held in two managed colonies. Chole- liths were analysed in one of the cases and consisted pre­dominantly of cholesterol. Since this cluster of cases, choleliths have not been noted in necropsies performed over 11 yr on more than 100 eastern barred bandicoots. This might indicate that the cases were a result of an anomalous risk factor (perhaps dietary) that has not been repeated.

ACKNOWLEDGEMENTS

I thank those who supplied and/or collated necropsy records to support the writing of this chapter. This includes Jo Ring of Melbourne Zoo, Jane Hall of Taronga Zoo, Nahiid Stephens of Murdoch University, Simone Vitali of Perth Zoo and Ian Smith from Zoos South Australia.