Diversity of protozoan parasites in a threatened marsupial (Petrogale penicillata) which is part of a conservation program
thesisposted on 28.03.2022, 10:41 by Elke T. Vermeulen
In conservation management, parasite communities are often only considered from a disease perspective, yet parasites are an important part of biodiversity. The role that parasites fulfil in conservation management is largely unknown. Hence, this research examines the biodiversity and prevalence of three protozoan parasites of the threatened brush-tailed rock-wallaby (BTRW, Petrogale penicillata) and more broadly, parasite diversity and specificity in the genus Petrogale, which contains seven species of conservation concern. The parasites of the seventeen Petrogale species are diverse with 157 species recorded across the genus. Parasite assemblages of Petrogale were found to have a significant relationship with the phylogeny (p = 0.008) and biogeography (p = 0.0001) of their hosts, and thus endemic parasites in threatened populations may be at risk of co-extinction. Faecal samples from brush-tailed rock-wallabies (BTRW) which were part of a conservation program were collected from nine sites under three categories: three sites with captive bred animals, four sites supplemented with captive bred animals and two sites with purely wild animals. Cryptosporidium sp. and Giardia sp. had a low prevalence across all BTRW sites, 7.1% (23/324) and 6.3% (20/318) respectively. No significant differences were observed in prevalence between site categories. Conversely, Eimeria was ubiquitous across all site categories, with an overall prevalence of 92.3% (108/117). The infection intensity (oocysts/gram faeces) of Eimeria did not vary significantly between site categories, but the highest variation was observed in supplemented sites. Cryptosporidium positive samples from two captive sites and one wild site contained the marsupial-specific C. fayeri and one captive and four wild samples were identified as the broader host range C. meleagridis using multi-locus genotyping (18S rRNA, actin and gp60 loci). Similarly, the anthropozoonotic G. duodenalis assemblage A was identified in eight supplemented, two captive and one wild sample, and assemblage B in seven supplemented and four wild samples using the 18S rRNA, β-giardin and gdh loci. The occurrence of parasite species associated with humans and domestic animals in BTRW indicates that these parasites are being transmitted via the environment as a result of contamination from non-wallaby sources. Next-generation sequencing (NGS) was used to examine the genetic structure of Eimeria communities. A new methodology incorporating a partial fragment of the 18S rRNA locus (450 bp) was developed to enable community analysis of Eimeria. Analyses revealed 28 Eimeria operational taxonomic units (OTUs) in 53 BTRW samples. This high biodiversity of Eimeria was maintained across all site categories with no significant difference in OTU richness or composition between sites or site categories. A high overlap in phylogeny and OTU composition was observed between captive bred and supplemented sites, suggesting geographical isolation of the captive bred populations may alter their Eimeria communities but further research is required to understand this variation. While no impact of the conservation program was detected on the BTRW parasites, anthropozoonotic parasites were present in both wild and captive BTRWs and thus present in their natural environment. As parasites of Australian wildlife are diverse and endemic, the parasite communities of endangered species need to be monitored, using similar methodology as this study, and considered within conservation management.