When the worm turns
Discovering more about the genetic mechanisms of parasitism is an important aspect of work at the Hopkirk Research Institute.
Parasitic nematodes infect hosts as diverse as aquatic life, plants, animals and man but, despite the huge impact that parasites have on health and economics, very little is known about the genetic mechanisms of parasitism.
One group of scientists investigating this at the Hopkirk is AgResearch's Molecular Parasitology team, and they are doing so with the help of a very unusual nematode - Parastrongyloides trichosuri.
"What makes this worm so unusual is its life cycle," says PhD student Susan Stasiuk.
"It is capable of being either a free-living nematode that lives in possum faeces on the forest floor, or a parasite that invades its host - the Australian brush-tailed possum. These worms assess their environment and then make the developmental decision to turn on genes that enable them to become a parasite or, under different environmental conditions, turn on other genes that enable them to become free-living."
Parasites usually need a host in which to reproduce, making it almost impossible to study the reproductive phase of the parasitic life-cycle or to manipulate them genetically. The option of a free-living cycle in P. trichosuri allows scientists to take them into the lab and grow them under laboratory conditions in order to manipulate and study them.
In Susan's case, the research focuses on what triggers the switch that makes the P. trichosuri larva become free-living or parasitic. Despite this nematode being discovered in 1958, the AgResearch team, with funding from a Marsden Fund Grant, is the first in the world to study it.
The work in the Molecular Parasitology laboratories is an extension of an Outcomes Based Investment (OBI) into Possum Control - a collaborative project between AgResearch, Landcare Research, Department of Conservation, the Animal Health Board, regional councils and MAF, and funded by the Foundation for Research, Science and Technology (FRST). Under the OBI umbrella these collaborators have come together to form the National Research Centre for Possum Biocontrol, or NRCPB.
The aim behind the NRCPB's parasite research is to design worms with new artificial traits from introduced DNA or gene restructuring. The transgenic worm could be used to trigger a response in the possum that interferes with its reproductive system and renders it sterile. Infected possums will pass the transgenic nematode to other possums, slowly reducing possum numbers in a more efficient and humane way than bait-based controls.
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