Periodontal disease in free-ranging koalas (Phascolarctos cinereus) from the Mount Lofty Ranges, South Australia, and its association with koala retrovirus infection.

BACKGROUND: In northern Australian koala populations (Queensland and New South Wales), periodontal disease (gingivitis and periodontitis) is common while koala retrovirus subtype A is endogenous, with other subtypes transmitted exogenously. Koala retrovirus has been hypothesised to cause immune suppression and may predispose koalas to diseases caused by concurrent infections. In southern Australia populations (Victoria and South Australia) periodontal disease has not been investigated, and koala retrovirus is presumably exogenously transmitted. This study described oral health in South Australian koalas and investigated if an association between periodontal disease and koala retrovirus exists. METHODS: Oral health was examined for wild-caught koalas from the Mount Lofty Ranges (n = 75). Koala retrovirus provirus was detected in whole blood using nested PCR and proviral load determined with qPCR. Periodontal disease severity was recorded and used to calculate the Final Oral Health Index (0-normal, 24-severe).Results Periodontal disease was observed in 84% (63/75) of koalas; 77% had gingivitis (58/75) and 65% (49/75) had periodontitis. The average Final Oral Health Index was 5.47 (s.d 3.13). Most cases of periodontal disease were associated with the incisors. Koala retrovirus-infected koalas were more likely to present with periodontitis (p = 0.042) and the Final Oral Health Index was negatively correlated with proviral load (ρ = -0.353, p = 0.017). CONCLUSION: South Australian koalas had a high prevalence of gingivitis and periodontitis. Periodontal disease was more prevalent in the incisors. Exogenous koala retrovirus infection may also facilitate the development of periodontitis by modulation of the immune response to concurrent oral bacterial infections.

Malocclusions in the koala (Phascolarctos cinereus).

Malocclusions are a misalignment or incorrect positioning of the teeth when the upper and lower jaws close. These are poorly described in the koala and can result in irregular mastication which can have lifelong effects on body condition and oral health. A total of 370 koalas from two populations in Queensland (295) and one in South Australia (75) were examined for malocclusions. The prevalence of malocclusions in South Australian free-ranging koalas, captive Queensland koalas and Queensland free-ranging koalas was 39% (44), 30% (29) and 22% (29) respectively. Four types of malocclusion were identified based on severity of misalignment of the incisor/canine region, types 1, 2, 3 and 4. Maxillary overbite measurements of the molariform teeth were determined and these anisognathic values were then used to describe malocclusions within familial relationships in captive colonies. Captive koalas with a malocclusion had narrower mandibular width that ranged between 0.5 and 1% less than the normal measurements. The specific malocclusions reported in this study affected individuals by leading to tooth rotation, mobility and erosion with inefficient mastication of food and vegetation compaction. These changes increased the oral cavity pathology, by placing animals at risk of periodontal disease. There was evidence of familial links to malocclusion types in captive animals. Therefore captive breeding recommendations should consider known koala malocclusion traits to minimise their effect on future generations.