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.

Diffusion during dehydrogenase reactions: the effects of intermediate electron acceptors.

A hamster cheek pouch model has been used to study the diffusion of reactants from the epithelium into adjacent muscle and connective tissue during the histochemical demonstration of glucose-6-phosphate dehydrogenase activity. The effects of the addition of intermediate electron acceptors to the incubation medium varied considerably from one acceptor to another, but were independent of the grade of polyvinyl alcohol incorporated into the medium. Menadione was the least effective intermediate both in transferring reducing equivalents from the primary dehydrogenase to Neotetrazolium chloride and in preventing diffusion. Phenazine methosulphate, Methylene Blue and Thionin were more efficient intermediates. Nevertheless, considerable diffusion occurred in the presence of Phenazine methosulphate, although very little diffusion was detectable with either of the thiazine dyes. It is suggested that these differences are related to different modes and sites of action of the carriers.