Using non-invasive sampling methods to determine the prevalence and distribution of Chlamydia pecorum and koala retrovirus in a remnant koala population with conservation importance

Abstract

Context. Pathogenic infections are an important consideration for the conservation of native species, but obtaining such data from wild populations can be expensive and difficult. Two pathogens have been implicated in the decline of some koala (Phascolarctos cinereus) populations: urogenital infection with Chlamydia pecorum and koala retrovirus 5 subgroup A (KoRV-A). Pathogen data for a wild koala population of conservation importance in South Gippsland, Victoria are essentially absent.Aims. This study uses non-invasive sampling of koala scats to provide prevalence and genotype data for C. pecorum and KoRV-A in the South Gippsland koala population, and compares pathogen prevalence between wild koalas and koalas in rescue shelters. 10 Methods. C. pecorum and KoRV-A provirus were detected by PCR of DNA isolated from scats collected in the field. Pathogen genetic variation was investigated using DNA sequencing of the C. pecorum ompA and KoRV-A env genes.Key results. C. pecorum and KoRV-A were detected in 61% and 27% of wild South Gippsland individuals tested, respectively. KoRV-A infection tended to be higher in shelter koalas compared with wild koalas. In contrast with other Victorian koala populations sampled, greater pathogen diversity was present in South Gippsland. 15 Conclusions. In the South Gippsland koala population, C. pecorum is widespread and common whereas KoRV appears less prevalent than previously thought. Further work exploring the dynamics of these pathogens in South Gippsland koalas is warranted and may help inform future conservation strategies for this important population.Implications. Non-invasive genetic sampling from scats is a powerful method for obtaining data regarding pathogen prevalence and diversity in wildlife. The use of non-invasive methods for the study of pathogens may help fill research 20 gaps in a way that would be difficult or expensive to achieve using traditional methods.

Koala immunogenetics and chlamydial strain type are more directly involved in chlamydial disease progression in koalas from two south east Queensland koala populations than koala retrovirus subtypes

“…Our findings also strengthen a growing body of data that support the infecting chlamydial strain as an important contributor for chlamydial disease progression in koalas 9 , 11 , 12 , 32 . Our approach was to combine a MLST scheme, which has been shown to be congruent with whole genome phylogeny and is a robust method for investigating genetic diversity 33 , with omp A genotyping, which appears to capture more genetic diversity due to the polymorphic nature of the omp A gene.…”

“…Variation in environmental factors exists between MB and HV in terms of rainfall, soil, vegetation communities, sympatry with livestock and proximity to human habitation. While evidence linking 'habitat quality' and chlamydial disease progression is inconclusive 18,32 , climate stress can impact population health 47,48 and HV was drought-affected at the time of our study. Many of the koalas at HV also shared their habitat with cattle, and the likelihood and frequency of cross-host transmission of chlamydial strains from livestock to koalas is currently unknown 33 .…”

Koala retrovirus load and non-A subtypes are associated with secondary disease among wild northern koalas

“…However, transcriptional silencing of germline integrations is incomplete and re-integration of KoRV into somatic cells within certain tissues is frequent [ 21 , 22 ]. Additionally, KoRV-A is present in southern koalas at low copy numbers per host cell, which is suggestive of exogenous infection [ 16 , 17 ], and appears to be exogenously transmitted from mothers’ to their joeys in northern koalas [ 23 ]. The ability of KoRV-A to cause disease is difficult to assess in northern populations as it is ubiquitous.…”

Helping koalas battle disease – Recent advances inChlamydiaand koala retrovirus (KoRV) disease understanding and treatment in koalas

“… 2017 ; Wedrowicz et al . 2018 ). Surveys from across Australia have identified 15 unique ompA genotypes in koalas (Fig.…”