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Parasitism by Ophidascaris robertsi with associated pathology findings in a wild koala (Phascolarctos cinereus)
  1. Viviana Gonzalez-Astudillo1,
  2. Lyn Knott2,
  3. Ludovica Valenza2,
  4. Joerg Henning2 and
  5. Rachel Allavena2
  1. 1California Animal Health and Food Safety Laboratory System, University of California Davis, San Bernardino, California, USA
  2. 2School of Veterinary Science, The University of Queensland, Brisbane, Queensland, Australia
  1. Correspondence to Dr Rachel Allavena; r.allavena{at}


Five third-stage Ophidascaris robertsi larvae, a python parasite, were recovered from a free-ranging mature male koala, Phascolarctos cinereus, from South-East Queensland. Most larval nematodes were found obstructing several hepatic blood vessels including the portal vein, causing vascular dilation. Despite the low number of parasitic larvae found, the large size of the larval third stage can lead to circulatory impairment of affected organs. Koalas may acquire O robertsi infection possibly by performing geophagy or soil ingestion, contaminated with eggs from python faeces. This is the first report of O robertsi in koalas indicating infection and subsequent pathological changes within the vasculature and liver.

  • koala
  • nematodes
  • wild animals
  • pathology
  • parasitology

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  • Contributors VGA conducted the research and drafted the manuscript. LK performed the parasitology identification and helped take figure images. LV helped perform the necropsy, assisted in documenting the gross findings and taking images of the gross findings. JH codirected the koala pathology research project with RA and helped do data analysis on the cases. As the senior diagnostic pathologist, RA reviewed the gross and microscopic findings of the cases, drafted and edited the manuscript and was codirector of the pathology research project.

  • Funding This research received no specific grant from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests None declared.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Data availability statement No additional data are available.

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