Intraorbital anatomy of the koala (Phascolarctos cinereus)

Refractory otitis media and otitis externa in a koala (Phascolarctos cinereus) treated with total ear canal ablation and lateral bulla osteotomy

BACKGROUND

To the authors' knowledge, this is the first report fully describing the surgical and medical management of otitis media and otitis externa in the koala (Phascolarctos cinereus) treated by total ear canal ablation and lateral bulla osteotomy.

CASE REPORT

An adult male koala captured as part of a monitoring project in South East Queensland was diagnosed with chlamydial cystitis. Purulent discharge from the right ear was also observed; diagnostic imaging was consistent with otitis media and otitis externa. Yokenella regensburgei was repeatedly cultured from the site. Clinical signs resolved with topical antibiotic therapy; however, recrudesced following cessation of antibiotics. A total ear canal ablation and lateral bulla osteotomy was performed, followed by an extended period of systemic antibiotic therapy. Mild facial nerve paresis was observed for 4 weeks postoperatively and resolved spontaneously. The koala remained clinically healthy for the 6 months it was monitored following release.

CONCLUSION

Total ear canal ablation combined with lateral bulla osteotomy appears to be an appropriate surgical intervention for otitis media combined with otitis externa refractory to medical management in the koala. Transient postoperative facial nerve paresis is a possible complication, as documented in other species. To the authors' knowledge this is the first case of Yokenella regensburgei infection outside of humans and American alligators (Alligator mississippiensis); the clinical significance of this pathogen in the koala remains unknown.

Case series: Computed tomography (CT) demonstrates lacrimal canal involvement in koalas (Phascolarctos cinereus) with maxillary incisor dental disease

Dental disease is common in wild and captive koalas. Effective treatments are limited and dental disease may not be recognised until it is quite severe. We describe the appearance of varying severities of dental disease on computed tomography (CT) images in a case series of six koalas. This case series demonstrates the use of CT to detect both mild and severe dental disease in koalas. The study also documents the normal CT appearance of the nasolacrimal duct in the koala. The only clinical abnormality in koalas with the mildest dental disease was ocular discharge. Computed tomography findings associated with ocular discharge were periapical lysis of first maxillary incisors, lacrimal canal remodelling and subsequent nasolacrimal duct obstruction. Dental disease should be a differential diagnosis for ocular discharge in koalas and CT examination enables visualisation of early stages of dental disease.

Anatomical and Radiographic Study on the Skull and Mandible of the Common Opossum (Didelphis Marsupialis Linnaeus, 1758) in the Caribbean

Common opossums (Didelphis marsupialis) are found throughout the Caribbean island of Trinidad and Tobago. The present work was conducted on 10 skulls and mandibles of the common opossum to describe the osteology and foramina of these skulls and mandibles grossly and radiographically. The information that is garnered can be used to detect, diagnose, and treat head affections, as well as for comparative studies with the skulls and mandibles of other similar species. The skulls and mandibles were prepared and cleaned using standard method. All of the characteristic features of various standards views of the skulls bones, including dorsal, lateral, caudal and midsagittal, and the lateral and caudal views of the mandibles as well as the foramina of the skulls and mandibles were described and discussed. Each skull was divided into long facial and short cranial regions. No supraorbital foramen was observed in the skulls. The tympanic bulla was absent while there was the tympanic process of the alisphenoid. The temporal process of the zygomatic bone, zygomatic process of maxilla, and zygomatic process of the squamosal bone formed the zygomatic arch. The dental formula was confirmed. The bones and foramina of the skull and mandible were similar to other marsupial species and were homologue to that of other mammals.

Anterior chamber collapse syndrome in a koala

BACKGROUND

Anterior chamber collapse syndrome has been recognised in various species and is associated with early-life ocular disease or trauma. It is important to differentiate this acquired condition from a congenital malformation.

CASE REPORT

An adult female koala (Phascolarctos cinereus) was referred for assessment of buphthalmos and severe keratitis of the right eye. The degree of keratitis obstructed examination of intraocular structures. Enucleation of the affected eye was performed and the histopathological diagnosis was anterior chamber collapse syndrome and secondary glaucoma. This case contributes to the limited information available in the literature on anterior chamber collapse syndrome, a disease unique in having secondary glaucoma with minimal or no inflammation. The case also expands the literature available on ocular disease in koalas. More specifically, this is the only reported case of glaucoma, of any aetiology, in the koala.