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Infection & disease

Atypical presentation of Cryptococcus neoformans in a koala (Phascolarctos cinereus): a magnetic resonance imaging and computed tomography study

Martínez-Nevado, E, Alonso-Alegre, EG, Martínez, MÁ, Rodríguez-Álvaro, A, de Merlo, EM, García, JG & Real, IG 2017, Journal of Zoo and Wildlife Medicine, vol. 48, no. 1, pp. 250-254.

Magnetic resonance imaging (MRI) and computed tomography (CT) are valuable tools for diagnosing cryptococcosis in koalas as the techniques, used together, can assist in identifying the precise location and extent of a granuloma.

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Case study: Iatrogenic diabetes mellitus in a koala (Phascolarctos cinereus) receiving treatment with prednisolone

Lathe, SE 2016, Journal of Wildlife Rehabilitation, vol. 36, no. 2, pp. 7-10.

A female koala that was brought into a wildlife hospital developed diabetes mellitus during treatment with prednisolone. After cessation of prednisolone treatment, blood glucose levels in the koala decreased to below the nominal reference range.

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Characterisation of CD4 T cells in healthy and diseased koalas (Phascolarctos cinereus) using cell-type-specific monoclonal antibodies

Manger, C, Armitage, CW, Timms, P, Corcoran, LM & Beagley, KW 2016, Developmental and Comparative Immunology, vol. 60, no. 1, pp. 80-90.

An initial cell-type-specific monoclonal antibody (mAb) for koalas has been developed. The anti-CD4 mAb is able to detect CD4+ T lymphocytes at various bodily sites using a range of analytical techniques. The mAb can also be used to detect vaccine-induced Chlamydia-specific CD4+ T cells in the peripheral blood mononuclear fragments of immunised koalas.

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Characterisation of the koala biovar of Chlamydia pneumoniae of four gene loci – ompAVD4, ompB, 16S rRNA, groESL spacer region

Wardrop, S, Fowler, A, O’Callaghan, P, Giffard, P & Timms, P 1999, Systematic and Applied Microbiology, vol. 22, pp. 22-27. 

While there is significant genetic diversity in Chlamydia pecorum strains that infect koalas, little is known about genetic diversity of C. pneumoniae. DNA sequences of four gene fragments were found to be different between koala, human and horse C. pneumoniae biovars. Two gene loci, ompAVD4 and ompB, were identical among all isolates from koalas. This study, for the first time, reports on a respiratory infection associated with C. pneumoniae in a captive koala population.

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Detection of koala retrovirus subgroup B (KoRV-B) in animals housed at European zoos

Fiebig, U, Keller, M & Denner, J 2016, Archives of Virology, vol. 161, pp. 3549-3553.

In addition to the common endogenous koala retrovirus KoRV-A, a second type of non-endogenous retrovirus, KoRV-B, was recently detected in animals in zoos in Japan and the United States. This study describes a different type of KoRV-B detected in koalas from zoos in Germany and Belgium.

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Epidemiology of chlamydial infection and disease in a free-ranging koala (Phascolarctos cinereus) population

Nyari, S, Waugh, CA, Dong, J, Quigley, BL, Hanger, J, Loader, J, Polkinghorne, A & Timms, P, 2017, PloS One, vol. 12, no. 12, e0190114.

The aim of this study was to analyse the epidemiology of infection and disease caused by Chlamydia in a koala population from Queensland. It was found that, out of 160 koalas tested, 31% were positive for Chlamydia and 28% exhibited clinical signs of chlamydial disease, with most infections observed at the urogenital and ocular sites.

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Epizootiology of Chlamydia infections in two free-range koala populations

Jackson, M, White, N, Giffard, P & Timms, P 1999, Veterinary Microbiology, vol. 65, no. 1, pp. 255-264.

This study is the first to use DNA-based assay techniques to compare the prevalence and epizootiology of the chlamydial species infecting koalas in two free-ranging koala populations in Queensland.

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Expression and in vitro upregulation of MHCII in koala lymphocytes

Lau, Q, Canfield, PJ & Higgins, DP 2012, Veterinary Immunology and Immunopathology, vol. 147, pp. 35-43.

The purpose of this study was to characterise class II major histocompatibility complex (MHCII) in koalas in terms of abundance and distribution between sexes and seasons, and further to evaluate MHCII as a marker of lymphocyte activation during in vitro studies. Flow cytometry found that the expression of MHCII was upregulated within activated B lymphocytes in cell culture, but not koalas with active inflammation. Furthermore, MHCII was found to be expressed predominantly on circulating B lymphocytes rather than on T lymphocytes.

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Genetic diversity of Chlamydia pecorum strains in wild koala locations across Australia and the implications for a recombinant C. pecorum major outer membrane protein based vaccine

Kollipara, A, Polkinghorne, A, Wan, C, Kanyoka, P, Hanger, J, Loader, J, Callaghan, J, Bell, A, Ellis, W, Fitzgibbon, S, Melzer, A, Beagley, K & Timms, P 2013, Veterinary Microbiology, vol. 167, pp. 513-522.

The genetic diversity of Chlamydia pecorum strains in koalas has limited the production of an effective cross-strain vaccine. By examining C. pecorum isolates from koalas across their range, the most common major outer membrane protein (MOMP) amino type F was suggested to be a prime candidate for recombinant C. pecorum vaccine development.

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Heterogeneity of koala retrovirus isolates

Shimode, S, Nakagawa, S, Yoshikawa, R, Shojima, T & Miyazawa, T 2013, FEBS Letters, vol. 558, pp. 41-46.

Koala retrovirus (KoRV) is a gammaretrovirus implicated in immune suppression and leukemia, with three subgroups identified named A, B and J. Phylogenetic analysis demonstrated that KoRV-B and KoRV-J should be considered the same subgroup. A long terminal repeat (LTR) in KoRV-B had four 17 bp tandem repeats (‘DR-1’ for direct repeat 1) and in KoRV-J had three 37 bp tandem repeats (‘DR-2’). The promoter activity in the KoRV-J OJ-4 strain was stronger than in KoRV-A, suggesting more efficient replication.

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Histopathological and immunohistochemical investigation of naturally occurring chlamydial conjunctivitis and urogenital inflammation in koalas (Phascolarctos cinereus)

Hemsley, S & Canfield, PJ 1997, Journal of Comparative Pathology, vol. 116, no. 1, pp. 273-290.

This study reports the findings of a histopathological (changes in tissue as a result of disease) and immunohistochemical (using antibodies to test for antigens in tissue) examination of the conjunctiva and lower urogenital tract of koalas exhibiting symptoms of chlamydial disease. Antibodies were used to label T and B lymphocytes, plasma cells, major histocompatibility complex class II (MHC II)-positive cells and chlamydial antigen in order to improve our knowledge of the immune response and pathogenesis of chlamydiosis.

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Histopathological examination of the pancreas of the koala (Phascolarctos cinereus)

Higgins, DP & Canfield, PJ 2009, Journal of Comparative Pathology, vol. 140, no. 1, pp. 217-224.

Autolysis of pancreatic tissue from koalas was previously thought to make these samples unsuitable for histopathological examination; however, this study demonstrates that many abnormalities of the pancreas can be detected using established criteria for the stages of autolysis up to 72 hours post mortem.

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Identification of koala T lymphocytes using an anti-human CD3 antibody

Wilkinson, R, Barton, M & Kotlarski, I 1995, Developmental and Comparative Immunology, vol. 19, no. 6, pp. 537-545.

Studying the immunobiology of koalas is important because koalas are prone to disease. Recently a new antibody, anti-CD3, has become available. To date koala T cells have not been identified using classic techniques. This study used anti-CD3 antibody to successfully bind T lymphocytes from koala’s peripheral blood. Anti-CD3 was found to bind a small polypeptide, likely similar to the original target – epsilon chain of the human CD3 complex.

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Identification, characterisation and expression analysis of natural killer receptor genes in Chlamydia pecorum infected koalas (Phascolarctos cinereus)

Morris, KM, Mathew, M, Waugh, C, Ujvari, B, Timms, P, Polkinghorne, A & Belov, K 2015, BMC Genomics, vol. 16, no 796.

The aim of this study was to characterise genes within the receptor clusters of natural killer (NK) cells of the koala. Analysis with quantitative polymerase chain reaction (qPCR) found that CLEC4E was upregulated in response to Chlamydia pecorum infection.

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Immuno-histochemical demonstration of the role of Chlamydiaceae in renal, uterine and salpingeal disease of the koala, and demonstration of Chlamydiaceae in novel sites

Higgins, DP, Hemsley, S & Canfield, PJ 2005, Journal of Comparative Pathology, vol. 133, no. 1, pp. 164-174.

The purpose of this study was to examine the distribution of chlamydial organisms in the kidneys and female upper reproductive tract of the koala and consequently characterise their role in disease. It was found that Chlamydiaceae contribute significantly to renal, uterine and salpingeal disease. Additionally, the report details a case study of a concurrent systemic infection with Chlamydiaceae and Gram-positive cocci.

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In vitro characterisation of koala Chlamydia pneumoniae: Morphology, inclusion development and doubling time

Mitchell, CM, Matthews, SA, Theodoropoulos, C & Timms, P 2009, Veterinary Microbiology, vol. 136, no. 1, pp. 91-99.

The Chlamydia pneumoniae koala nasal isolate termed LPCoLN was compared to the human isolate AR39 and differed significantly from the human isolate in terms of doubling time, size, and morphology.

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In vitro survival characteristics of koala Chlamydiae

Rush, CM & Timms, P 1996, Wildlife Research, vol. 23, no. 1, pp. 213-219.

Type I and II koala Chlamydia strains were compared to an avian C. psittaci strain. All three strains survived 4 hours of exposure to solutions ranging from pH 4 to 10, with Type I surviving best at pH 7.2-7.5 and Type II surviving optimally at pH 7.0-7.2. Type 1 elementary bodies remained viable for 28 days at temperatures of 18-23°C, but were inactivated within 5 minutes at 56°C. Avian chlamydiae survived 4-6 days after drying, whereas koala Type I only survived 2-4 days. Type I was also still infective after three days exposure on Eucalyptus tereticornis leaves. Overall, these results demonstrated that koala Type I Chlamydia is able to survive significant time periods under extreme conditions, meaning that non-sexual transmission is a possible transmission mechanism for the strain.

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Increased genetic diversity and prevalence of co-infection with Trypanosoma spp. in koalas (Phascolarctos cinereus) and their ticks identified using next-generation sequencing (NGS)

Barbosa, AD, Gofton, AW, Paparini, A, Codello, A, Greay, T, Gillett, A, Warren, K, Irwin, P & Ryan, U 2017, PLoS ONE, vol. 12, no. 7, e0181279.

Protozoan infections by Trypanosoma species can affect koala health. In this study koalas were found to harbor many different species of trypanosomes, and mixed infections by multiple species were more common than single infections. T. irwini was found to be the dominant species. Ticks collected from koalas may play a role in trypanosome transmission.

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Interleukin 17A is an immune marker for chlamydial disease severity and pathogenesis in the koala (Phascolarctos cinereus)

Mathew, M, Waugh, C, Beagley, KW, Timms, P & Polkinghorne, A 2014, Development and Comparative Immunology, vol. 46, pp. 423-429.

Chlamydial disease is a significant threat to the survival of koala populations, with management and control of this pathogen restricted by a narrow insight into the koala’s immune response. To develop a greater understanding of koala immunology, this study outlined the cytokine responses of immune cells sampled from koalas possessing chlamydial disease with varying stages of severity. Four different cytokines were targeted for inspection. Findings revealed significantly higher gene expression of Interleukin (IL) 17A (Th17 cytokine) in those koalas currently affected by chlamydial disease than those unaffected.

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Keratitis in free-ranging koalas (Phascolarctos cinereus) on Magnetic Island, Townsville

Hirst, LW, Brown, AS, Kempster R, Hall, J & Woolcock, JB 1992, Journal of Wildlife Diseases, vol. 28, no. 3, pp. 424-427.

Investigation of 70 free-ranging koalas from Magnetic Island, Queensland revealed that unilateral keratitis was present in 12 koalas and bilateral keratitis in a further 10 koalas. No Chlamydia psittaci was detected in any of the animals and disregarding various other medical conditions such as nasal discharge, there appeared to be no indication of ocular chlamydial infection.

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Koala retrovirus genotyping analyses reveal a low prevalence of KoRV-A in Victorian koalas and an association with clinical disease

Legione, AR, Patterson, JLS, Whiteley, P, Firestone, SM, Curnick, M, Bodley, K, Lynch, M, Gilkerson, JR, Sansom, FM & Devlin, JM 2017, Journal of Medical Microbiology, vol. 66, pp. 236-244.

The endogenisation of koala retrovirus (KoRV) has resulted in 100% prevalence of KoRV in koalas from New South Wales and Queensland. In contrast, this study found that there was a 24.7% prevalence of KoRV in koalas from Victoria. Additionally, the KoRV provirus was twice as likely to be detected in koalas exhibiting clinical symptoms of KoRV, such as ‘wet bottom’, than in koalas without symptoms.

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Lack of antiviral antibody response in koalas infected with koala retroviruses (KoRV)

Fiebig, U, Keller, M, Moller, A, Timms, P & Denner, J 2015, Virus Research, vol. 198, pp. 30-34.

The purpose of this study was to screen koala sera for antibodies against endogenous koala retrovirus, KoRV-A. Polymerase chain reaction (PCR) identified endogenous KoRV-A from the sera of all 16 koalas tested, with two koalas positive for exogenous KoRV-B. Further protein analyses with Western blot failed to identify antibodies specific for KoRV-A, which could indicate a state of tolerance.

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Microbiota composition of the koala (Phascolarctos cinereus) ocular and urogenital sites, and their association with Chlamydia infection and disease

Vidgen, ME, Hanger, J & Timms P 2017, Scientific Reports, vol. 7, article 5239

This study explored the potential associations between microbiota profiles at penile/urogenital and ocular sites, chlamydial infection status, and demographic factors in free-ranging koalas. It was found that the presence or absence of particular microbiota in the female urogenital tract may contribute to the progression of Chlamydia pecorum infection to disease at the site. Penile and urogenital tract microbiota, but not ocular microbiota, were also found to differ between the sexes and life stages.

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Molecular characterisation and expression analysis of Interferon gamma in response to natural Chlamydia infection in the koala, Phascolarctos cinereus

Mathew, M, Pavasovic, A, Prentis, PJ, Beagley, KW, Timms, P & Polkinghorne, A 2013, Gene, vol. 527, pp. 570-577.

Transcriptome analyses of koalas have identified the sequence of the genes encoding koala interferon gamma (IFNγ), a cytokine involved in antimicrobial responses. By comparing tissues from cohorts of koalas with and without active Chlamydia infections using quantitative real time PCR (qPCR), significantly different expression patterns of IFNγ between both groups were observed.

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Molecular evidence for novel chlamydial infections in the koala (Phascolarctos cinereus)

Devereux, LN, Polkinghorne, A, Meijer, A & Timms, P 2003, Systematic and Applied Microbiology, vol. 26, pp. 245-253.

Infection with Chlamydia is common in wild koalas. C. pecorum and C. pneumoniae largely infect the eye, the genitourinary tract and the respiratory system of the koala. In this study, a commonly used method of polymerase chain reaction (PCR) was used to detect nine novel Chlamydia-like strains infecting koalas. A new technique using fragments of ribosomal RNA (rRNA) gene was developed to further evaluate these additional strains.

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Morbidity and Mortality in the Koala (Phascolarctos cinereus)

Backhouse, TC & Bolliger, A 1961, Australian Journal of Zoology, vol. 9, no.1, pp. 24-37.

Of 28 koalas autopsied in 1960, pneumonia was the leading cause of death in this mortality study, which also presented as a comorbidity with trauma. Other significant causes of death were hepatitis, yeast infections of the species Cryptococcus neoformans, leukaemia and anaemia. Ovarian cysts were observed in a number of the koalas, but it was only the cause of death for koalas whose cysts had become infected. Finally, senility-associated diseases such as cardiac failure were seen at a low level.

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Multiple intra-abdominal serosal myxosarcomas in two koalas (Phascolarctos cinereus)

Gonzalez Astudillo, V, Schaffer-White, A, Allavena, R & Palmieri, C 2015, Journal of Comparative Pathology, vol. 152, pp. 183-286.

Post-mortem examinations performed on two koalas revealed a thick accumulation of fluid in the abdomens. Many hard lumps filled with fluid were also found spread across the abdominal cavities. When examined under the microscope the lumps were found to contain cancer cells.

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One hundred twenty years of koala retrovirus evolution determined from museum skins

Avila-Arcoa, MC, Ho, SYW, Ishida, Y, Nikolaidis, N, Tsangaras, K, Hönig, K, Medina, R, Rasmussen, M, Fordyce, SL, Calvignac-Spencer, S, Willerslev, E, Gilbert, MTP, Helgen, KM, Roca, AL & Greenwood, AD 2013, Molecular Biology and Evolution, vol. 30, no. 2, pp. 299-304.

Historical DNA samples from museum-held koala skins displayed comparable proviral koala retrovirus (KoRV) envelope sequences to extant samples, suggesting the spread and subsequent infection of KoRV occurred over a greater period of time than previously thought. Being the only known retrovirus to be currently infecting its host’s germ line, KoRV has remained an issue for koalas since the 19th century and may have actually increased the susceptibility of koalas to chlamydial infection as a result of its evolving and expeditious nature. 

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Outer membrane protein 2 gene sequences indicate that Chlamydia pecorum and Chlamydia pneumoniae cause infections in koalas

Glassick, T, Giffard, P & Timms, P 1996, Systematic and Applied Microbiology, vol. 19, no. 1, pp. 457-464.

Seven strains of Chlamydia present in koalas that were all previously described as types of Chlamydia psittaci have been reclassified as either C. pneumoniae or C. pecorum following genetic sequence and phylogenetic analyses.

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Outer membrane protein A gene sequencing demonstrates the polyphyletic nature of koala Chlamydia pecorum isolates

Jackson, M, Giffard, P & Timms, P 1997, Systematic and Applied Microbiology, vol. 20, no. 1, pp. 187-200.

When the phylogenetic relationships of sequences of a chlamydial major outer membrane protein gene from Chlamydia pecorum isolates of both koala and non-koala origin were examined, the genotypes sequenced were found to be genetically distinct. Rather than being represented as a single branch in the C. pecorum phylogenetic tree, the koala isolates separated into five unique genotypes. Of these five genotypes, two were specific to koalas, and three were shared with sheep, cattle or pigs.

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Papillomavirus in healthy skin of Australian animals

Antonsson, A & McMillan, NAJ 2006, Journal of General Virology, vol. 87, no. 1, pp. 3195-3200.

Papillomaviruses have been detected in one monotreme and two marsupial species in Australia, including the koala. From samples taken from several captive animal environments across Queensland including Lone Pine Koala Sanctuary, three putative and potential new papillomavirus types in koalas were identified. Of those koalas sampled, 14% tested positive for papillomavirus DNA attributable to one of these three papillomavirus types. The putative new koala papillomavirus type KoAA1 is genetically distinct from all previously described human and animal papillomaviruses.

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Parasitic pneumonia in a koala (Phascolarctos cinereus) from Victoria, Australia

McColl, KA & Spratt, DM 1982, Journal of Wildlife Diseases, vol. 18, no. 4, pp. 511-512.

A very sick, mature male koala was presented to the Veterinary Research Institute, Victoria where examination showed only arthritis in the stifle joint. Microscopic analysis of lung tissue revealed a mild parasitic interstitial pneumonia. In the koala, a range of disease syndromes have been described, yet until now none have resulted from infiltration by parasitic helminths.

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Phylogenetic diversity of koala retrovirus within a wild koala population

Chappell, KJ, Brearley, JC, Amarilla, AA, Watterson, D, Hulse, L, Palmieri, C, Johnston, SD, Holmes, EC, Meers, J & Young, PR 2017, Journal of Virology, vol. 91, no. 3, e01820-16.

Koala retrovirus (KoRV) is widespread throughout koala populations, both wild and captive, and yet only nine different KoRV envelope sequences have thus far been described. From 18 koalas sampled from free-ranging populations in south-east Queensland, 108 unique sequences and four potentially new KoRV subtypes have been described here for the first time.

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Pneumonia due to Chlamydia pecorum in a koala (Phascolarctos cinereus)

Mackie, JT, Gillett, AK, Palmieri, C, Feng, T & Higgins, DP 2016, Journal of Comparative Pathology, vol. 155, no. 1, pp. 356-360.

This report documents a case of Chlamydia pecorum infection of the bronchiolar epithelium of the koala, causing pneumonia in a juvenile male.

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Prevalence and clinical significance of herpesvirus infection in populations of Australian marsupials

Stalder, K, Vaz, PK, Gilkerson, JR, Baker, R, Whiteley, P, Ficorilli, N, Tatarczuch, L, Portas, T, Skogvold, K, Anderson, GA & Devlin, JM 2015, PloS One, vol. 10, no. 7, p. e0133807.

To date, molecular classification of herpesviruses in marsupial species has been limited. In this study, the presence of herpesviruses in several Australian marsupial species, including koalas, was identified and assessed for risk factors seen during herpesvirus infection. It was found that the presence of Chlamydia pecorum DNA in koalas was highly associated with the presence of herpesvirus DNA, which could suggest a co-infection dynamic.

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Prevalence and pathologic features of Chlamydia pecorum infections in South Australian koalas (Phascolarctos cinereus)

Speight, KN, Polkinghorne, A, Penn, R, Boardman, W, Timms, P, Fraser, T, Johnson, K, Faull, R, Bate, S & Woolford, L 2016, Journal of Wildlife Diseases, vol. 52, no. 2, pp. 301-306.

Previously thought to be of low prevalence in South Australian populations, chlamydial infection has been detected in a significant proportion of a subset of koalas from the region. For these koalas, however, infection does not necessarily lead to clinical disease.

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Retrovirus mutation rates and their role in genetic variation

Mansky, LM 1998, Journal of General Virology, vol. 79, pp. 1337-1345.

This study reviews information regarding retrovirus variation and the impacts it may have on the diversity and evolution of viruses, virus severity, pathogenesis, and the development of antiviral drugs and vaccines. The information produced by this study can be applied to koalas to increase our understanding of koala retrovirus, or KoRV.

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Serological assessment of chlamydial infection in the koala by a slide EIA technique

Ueno, H, Mizuno, S, Takashima, I, Osawa, R, Blanshard, W, Timms, P, White, N & Hashimoto, N 1991, Australian Veterinary Journal, vol. 68, no. 12, pp. 393-396.

A slide enzyme immunosorbent assay (EIA) that can reliably detect Chlamydia psittaci antibody in koala blood serum is described in this study, presenting a rapid, simple and reliable alternative to existing methods.

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Skeletal fluorosis in marsupials: a comparison of bone lesions in six species from an Australian industrial site

Death, C, Coulson, G, Kierdorf, U, Kierdorf, H, Ploeg, R, Firestone, SM, Dohoo, I & Hufschmid, J 2017, Science of the Total Environment, vol. 584-585, no. 1, pp. 1198-1211.

Koalas and other marsupials living in high-fluoride environments are at risk of developing skeletal fluorosis. The severity of skeletal lesions in an affected animal is positively associated with bone fluoride levels. Of the six species studied here, all exhibited either localised or generalised periosteal hyperostosis but the distribution of lesions varied according to the animal’s mastication and gait.

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Streptobacillary pleuritis in a koala (Phascolarctos cinereus)

Russell, EG & Straube, EF 1979, Journal of wildlife Diseases, vol. 15, no. 3, pp. 391-394.

Streptobacillus moniliformis pleuritis was observed in a koala. There were granulomatous lesions observed, which occur when the immune system of an animal walls off foreign substances with macrophages due to being unable to eliminate the substance. A culture was made and inoculated in mice and rats, with the organism determined to be pathogenic for mice but not rats.

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The nucleotide sequence of koala (Phascolarctos cinereus) retrovirus: a novel type C endogenous virus related to gibbon ape leukaemia virus

Hanger, JJ, Bromham, LD, McKee, JJ, O’Brien, TM & Robinson, WF 2000, Journal of Virology, vol. 74, no. 9, pp. 4264-4272.

For the first time, the full nucleotide sequence of koala retrovirus (KoRV) is reported and characterised as a novel C-type endogenous retrovirus as a result. Phylogenetic analyses revealed a close genetic relationship between KoRV and gibbon ape leukaemia virus (GALV).

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Time-delayed influence of urban landscape change on the susceptibility of koalas to chlamydiosis

McAlpine, C, Brearley, G, Rhodes, J, Bradley, A, Baxter, G, Seabrook, L, Lunney, D, Liu, Y, Cottin, M, Smith, AG & Timms, P 2017, Landscape Ecology, vol. 32, no. 3, pp. 1-17.

The effects of changes in landscape or climate on the prevalence of chlamydiosis in koalas may not manifest until several years after the initial change occurred. Disease prevalence and body condition of koalas in southeast Queensland were quantified to determine both the spatial factors that affect these variables and the time delay, if any, of the effect. For landscapes in which the area of suitable habitat increased, koalas had high body condition scores but also high disease prevalence three years later. Alternatively, when the extent of urbanisation in a landscape increased, koala populations exhibited an increased prevalence of chlamydiosis four years later and decreased body condition one year later. An increase in annual rainfall was associated with immediately improved body condition and reduced disease prevalence after two years.

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Transspecies transmission of gammaretroviruses and the origin of the gibbon ape leukaemia virus (GaLV) and the koala retrovirus (KoRV)

Denner, J 2016, Viruses, vol. 8, no. 12, 336.

Koala retrovirus (KoRV) is closely related to gibbon ape leukaemia virus (GALV), and it is thought that they both originate from transspecies transmissions from the same host. Bats are discussed as a possible host of a retrovirus transmitted to gibbons and koalas as they could feasibly enter both gibbon habitats in Thailand and koala habitats in Australia and also carry several endogenous and exogenous retroviruses.

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Use of quantitative real-time PCR to monitor the shedding and treatment of chlamydiae in the koala (Phascolarctos cinereus)

Markey, B, Wan, C, Hanger, J, Phillips, C & Timms P 2007, Veterinary Microbiology, vol. 120, no. 1, pp. 334-342.

A quantitative real-time analysis revealed that antibiotic treatment for koalas with chlamydial infections caused chlamydiae to shed rapidly and in great numbers from both ocular and urogenital sites, with the majority of infections cleared after two weeks of treatment.

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Wasting disease in the koala, Phascolarctos Cinereus

Degabriele, R 1989, Perspectives in Biology and Medicine, vol. 32, no. 3, pp. 414-418.

This article provides a hypothesis for wasting disease in koalas. Some symptoms of wasting disease are weight loss and death in a coma with no indication of infection. Wasting disease is most common among very young, old and weak koalas, and particularly during winter or after droughts. In addition, a full stomach is often seen to accompany wasting disease.

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Within-population diversity of koala Chlamydophila pecorum at ompA VD1-VD3 and the ORF663 hypothetical gene

Higgins, DP, Beninati, T, Meek, M, Irish, J & Griffith, JE 2012, Veterinary Microbiology, vol. 156, pp. 353-358.

Chlamydophila pecorum is a bacterium that commonly infects koalas. This study evaluated the diversity of ompA VD1-3 gene and ORF663, a hypothetical gene, in koalas with chlamydia.

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