Clinical and microbiological aspects of periodontal disease in horses in South-East Queensland, Australia

Chinkangsadarn, Teerapol (2016). Clinical and microbiological aspects of periodontal disease in horses in South-East Queensland, Australia PhD Thesis, School of Veterinary Science, The University of Queensland. doi:10.14264/uql.2016.264

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Author Chinkangsadarn, Teerapol
Thesis Title Clinical and microbiological aspects of periodontal disease in horses in South-East Queensland, Australia
School, Centre or Institute School of Veterinary Science
Institution The University of Queensland
DOI 10.14264/uql.2016.264
Publication date 2016-06-03
Thesis type PhD Thesis
Supervisor Phillip S. Bird
Gary J. Wilson
Lisa Kidd
Sean Corley
Total pages 162
Language eng
Subjects 070707 Veterinary Microbiology (excl. Virology)
070704 Veterinary Epidemiology
070703 Veterinary Diagnosis and Diagnostics
Formatted abstract
The study of periodontal disease as part of equine dentistry is one of the overlooked fields of study, which truly needs more study and research to clearly understand the nature of the disease, the most appropriate diagnostic technique and prevention or treatment to provide for a good quality of life for horses.

The abattoir survey of the oral cavity and dentition of 400 horses from South-East Queensland, Australia, showed that the most common dental abnormality was sharp enamel points (55.3% prevalence). Several types of dental abnormalities were strongly associated with age. The highest frequency of dental abnormalities (97.5%) were observed in senior horses (11-15 years old) and this included periodontal disease that increased to almost fifty percent in senior horses. The findings also confirmed that all horses, not just young horses, should have regular complete dental examinations as early as possible which should limit the development of more severe dental pathologies later in life.

The equine oral microbiome found in dental plaque can cause oral disease which involves the some of the endogenous oral microbiota becoming opportunistic pathogens. The conventional method of oral microbiology based on culture dependent techniques usually overestimates the significance of species that are easily grown and overlooks microbial community diversity. Recently, the culture independent techniques using the next generation sequencing (NGS) method can determine the whole bacterial microbiota. The results from culture dependent and NGS method of analysis of healthy gingiva and periodontitis samples showed that the most common Genera isolated were Prevotella and Porphyromonas without a statistical significance in bacterial diversity, between the control and periodontitis groups. In conclusion, equine bacterial diversity between the healthy and periodontitis groups were similar which is different from other animals and this may be due to factors such as dentition, feed type and husbandry.

The standard approach for diagnosis of equine periodontal disease (EPD) is based on clinical dental examination but to evaluate the current stage of disease and for further treatment planning, auxiliary aids such radiography are required. Equine dental radiography has been largely restricted to extraoral techniques by the standard equine radiography technology and the complexity of equine head anatomy. In addition, superimposition and distortion of the cheek teeth arcade is a major problem for radiographic interpretation. Intraoral radiography has been largely ignored in horses, due to the uncooperative nature of these patients and the absence of dedicated technology unsuitable for equine oral radiography. In this study, radiographic images from seven horse heads obtained using a commercially available equine intraoral computed radiography system (IO-CR) and 3D imaging from computed tomography file sets were reviewed. IO-CR has shown potential as a diagnostic tool where key pathological lesions of EPD of the cheek teeth were demonstrated without superimposition from the opposite dental arcade. 3D imaging is also another useful technique that has shown clear areas of alveolar bone loss and the ability to calculate accurate attachment lost where periodontal lesions are present. However cost and availability restricts the use of 3D imaging as a routine procedure. In conclusion, IO-CR provides good quality radiographs that could be used in diagnosis and treatment planning for equine periodontal diseases.

The first in-vivo study of the effect of a commercial preparation of 1.4% w/v chlorhexidine gluconate (CHX, Hexarinse®) on sub-gingival plaque using NGS method was studied. Samples were collected from the equine oral cavity before and after a three month CHX trial. The data of both pre- and post-trial oral plaque profiles were compared with no significant changes in the bacterial community observed. However a narrower range, but not statistically significant bacterial diversity was observed in the CHX group. In conclusion, 1.4% w/v CHX has an influence on the bacterial community by narrowing the diversity range and reducing the numbers of some periodontal bacteria. An important factor in its efficacy appears to be the duration, dosage and interval between applications. The long term effect of oral application of CHX needs to be studied as it is possible it could affect the intestinal microbiome and lead to other health concerns.

In conclusion, dental abnormalities such as sharp enamel points and periodontal diseases are common in horses where EPD has a higher prevalence in senior horses. EPD can be diagnosed easier using IO-CR with high quality images, whereas 3D imaging is more suitable for research and academic studies. Bacterial isolates from the equine oral cavity have a complex diversity with the most frequent isolates belonging to the genus Bacteroides. Currently there are limitations with the databases for molecular identification of oral bacteria from the equine oral cavity. In addition, novel bacteria from the equine oral cavity are waiting to be discovered. The use of CHX as an oral rinse for horses has the potential for controlling and reducing the diversity of oral bacterial species but this was not shown to be significant in this study. The long term use and higher dose rates of CHX need further investigation due the effects of CHX on the intestinal microbiota.
Keyword Equine Dentistry
Periodontal Disease
Intraoral radiography
3 dimension imaging
Anaerobic bacteria
16S rRNA sequencing
Next generation sequencing

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Created: Mon, 23 May 2016, 17:42:41 EST by Teerapol Chinkangsadarn on behalf of Learning and Research Services (UQ Library)