Oral Presentation Australian Society for Microbiology Annual Scientific Meeting 2019

Parasites of land and sea: Comparative genomics of microbial eukaryotes Perkinsus olseni and Theileria orientalis. (#25)

Daniel R Bogema 1 , Jerald Yam 1 2 , Melinda L Micallef 1 , Sherin Alex 1 , Shayne Fell 1 , Jeffery Go 1 , Cheryl Jenkins 1 , Cecile Dang 3
  1. Elizabeth Macarthur Agricultural Institute, NSW Department of Primary Industries, Menangle, New South Wales, Australia
  2. The ithree institute, University of Technology Sydney, Ultimo, NSW, Australia
  3. Department of Primary Industries and Regional Development, Government of Western Australia, Perth, Western Australia, Australia

Perkinsus spp. are protozoan parasites that cause enormous losses to marine mollusc populations worldwide. In Australia, P. olseni has been linked to severe reductions in abalone populations. Significant and devastating reductions of NSW wild abalone populations have been observed since the 1990s, which has been attributed to a P. olseni outbreak (Liggins and Upston, 2010). In WA, P. olseni has been identified in several farmed and wild mollusc species and is considered a major threat to the state’s expanding abalone industry. As part of a larger project targeting this important parasite, we examined five P. olseni isolates and one P. chesapeaki isolate from local and international sources using Illumina short-read sequencing. We additionally sequenced an Australian isolate of P. olseni with an Oxford Nanopore MinION to produce a reference genome. Examination of these sequences has revealed differences in genome size and identity between isolates sourced from the Southern and Northern hemispheres. Notably, analysis of sequence read coverage indicates that regions commonly targeted for diagnostic quantitative PCR assays are potentially subject to substantive gene duplications that vary considerably between isolates.

Theileria orientalis Ikeda genotype is a tick-borne haemoparasite that can cause ill-thrift and anaemia in cattle. The introduction of this pathogenic genotype to naïve cattle in the early 2000s caused significant damage to cattle producers in Australia and the South Pacific (Watts et al, 2016). We previously sequenced an Australian-sourced Ikeda plus two benign genotypes (Chitose and Buffeli) and identified differences that could establish these genotypes as separate Theileria species (Bogema et al, 2018). However, the short-read-derived assemblies for these genotypes were severely fragmented. To further explore the genomic diversity of T. orientalis in Australia, we sequenced an additional 21 isolates of T. orientalis Ikeda variant from diverse locations and time-points. We also used nanopore sequencing technology to greatly improve the contiguity of Ikeda, Chitose and Buffeli genome sequences.

  1. Liggins G.W. and Upston J. (2010) Investigating and managing the Perkinsus-related mortality of blacklip abalone in NSW. Final Report FRDC Project 2004/084.
  2. Watts, J. G., M. C. Playford and K. L. Hickey (2016). Theileria orientalis: a review. N Z Vet J 64(1): 3-9.
  3. Bogema, D. R., M. L. Micallef, M. Liu, M. P. Padula, S. P. Djordjevic, A. E. Darling and C. Jenkins (2018). Analysis of Theileria orientalis draft genome sequences reveals potential species-level divergence of the Ikeda, Chitose and Buffeli genotypes. BMC Genomics 19(1): 298.