Dissertation
C. pecorum: Understanding modes of transmission and control of infection in vaccinated/antibiotic treated koalas (Phascolarctos cinereus)
University of the Sunshine Coast, Queensland
Doctor of Philosophy, University of the Sunshine Coast
2020
DOI:
https://doi.org/10.25907/00167
Abstract
Chlamydia infections of the Australian marsupial, Phascolarctos cinereus (koala) have contributed to population declines. Koala Chlamydia infections are transmitted directly through sexual interactions, direct contact, urine contamination and pap feeding and can result in a range of disease pathologies including conjunctivitis, reproductive disease, cystitis and nephritis. Treatment for koala chlamydiosis is currently limited to antibiotic therapy, which results in bacterial clearance and eventual disease regression. Unfortunately, antibiotic therapy in koalas also commonly results in gastrointestinal dysbiosis and death. Fortunately, a Chlamydia vaccine for koalas has been under development for several years. The most tested version of the Chlamydia koala vaccine has demonstrated induction of humoral immune responses and, importantly, a therapeutic response in koalas with mild conjunctival disease. Firstly, investigations into possible alternative modes of Chlamydia transmission were studied through the screening of concurrent infections of the conjunctiva, urogenital and gastrointestinal tract. Concurrent infections with Chlamydia were identified at the urogenital and rectal sites, with C. pecorum genotype G dominating in the gastrointestinal tract, and genotypes A and E' dominating in the urogenital tract. Gastrointestinal tract C. pecorum PCR positivity suggested that koala gastrointestinal tract infections are common and occur regularly in animals with concurrent genital tract infections. However, this study did not find evidence of Chlamydia strain contamination between the anatomical sites. This thesis then identified immunological changes at the urogenital mucosa of koalas with Chlamydia-induced cystitis that resulted in disease regression during antibiotic treatment. The aim of this investigation was to identify specific gene targets to enable monitoring during therapeutic vaccination. Through clinical microbiological and transcriptomic approaches, disease regression, bacterial clearance and innate immune responses were mapped in koalas with signs of Chlamydia-induced cystitis while receiving anti-Chlamydia antibiotics. Significant reduction in the signs of cystitis were observed both during, as well as post Finally, identification of gastrointestinal infections and the associations to disease prone sites have indicated evidence for tissue tropic genotypes. This work will aid future vaccine studies in the immunological identification of disease regression, vaccine induced adaptive immune responses and allow for accurate monitoring of bacterial shedding through the inclusion of the gastrointestinal mucosa.
Details
- Title
- C. pecorum: Understanding modes of transmission and control of infection in vaccinated/antibiotic treated koalas (Phascolarctos cinereus)
- Authors
- Samuel Phillips
- Contributors
- Peter Timms (Supervisor)
- Awarding institution
- University of the Sunshine Coast
- Degree awarded
- Doctor of Philosophy
- Publisher
- University of the Sunshine Coast, Queensland
- DOI
- 10.25907/00167
- Organisation Unit
- Centre for Bioinnovation; University of the Sunshine Coast, Queensland; School of Health and Sport Sciences - Legacy; School of Science, Technology and Engineering
- Language
- English
- Record Identifier
- 99451105002621
- Output Type
- Dissertation
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