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

Abstract

BackgroundTo 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 ReportAn 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.ConclusionTotal 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.

Yokenella regensburgei—Past, Present and Future

“…The combined medical and surgical approach of this case led to a favorable outcome and the animal was asymptomatic at six months follow-up. This report provides useful insights into the pathogenic potential of Y. regensburgei [31]. Based on the existing data, the emergence of this pathogen has a broader distribution than previously assumed.…”

“…An infection produced by Y. regensburgei in non-human mammals was recently recorded for the first time by Swaffield et al in 2023 in a case report of otitis in an australian koala bear (Phascolarctos cinereus) caught in the wild [31]. The animal was captured as part of a monitoring project and was initially diagnosed with bacterial cystitis [31]. However, they noticed a purulent discharge from one of the ears and bacteriologic analysis using 16S rRNA sequencing indicated Y. regensburgei as the etiologic agent [31].…”

“…An infection produced by Y. regensburgei in non-human mammals was recently recorded for the first time by Swaffield et al in 2023 in a case report of otitis in an australian koala bear (Phascolarctos cinereus) caught in the wild [31]. The animal was captured as part of a monitoring project and was initially diagnosed with bacterial cystitis [31].…”

“…The animal was captured as part of a monitoring project and was initially diagnosed with bacterial cystitis [31]. However, they noticed a purulent discharge from one of the ears and bacteriologic analysis using 16S rRNA sequencing indicated Y. regensburgei as the etiologic agent [31]. The infection presented multiple recurrences after the antibiotic treatment was stopped, ultimately requiring surgical intervention.…”