Where is the biotechnology in the possum biocontrol story?
Biological control, or biocontrol, is the use of a living organism, or the product of a living organism, to control the numbers of another organism, usually a pest. The potential advantages of biocontrol methods are that they are (a) sustainable and (b) very specific to the species being controlled.
Injecting nematode worms
Injecting the foreign DNA (the 'transgene') into the ovary of the female nematode worms requires a microscope.
Using a hormone toxin
In this example of possum biocontrol, a hormone toxin is used to interfere with the fertility of possums. In the short term, the hormone toxin may be distributed amongst the possum population using baits. This is expensive, because the baits would need to be re-applied.
Using a nematode worm to distribute the hormone toxin
A longer term, more sustainable option, is to distribute the toxin using a nematode worm — a parasite that is found naturally in possums and that could be used to spread the toxin amongst the possum population (if baits are used, they would need to be reapplied).
Genetically modifying worms to affect possum fertility
At AgResearch, scientists are modifying a parasitic worm that infects possums. The modified worm will be able to seriously reduce the fertility of possums that it infects. Dr. Warwick Grant explains that foreign DNA is injected into the ovaries of a female nematode. The baby nematodes that carry the foreign DNA (the 'transgene') are then selected and used for further research and testing.
Genetically modifying the nematode worm
The nematode worm would need to be genetically modified to produce the toxin. The biotechnology in this context involves the use of one living organism (the modified nematode) to control another (possums).
Using a hormone-toxin to control possum numbers
Dr Warwick Grant and Dr Doug Eckery are investigating the effects of a toxin (poison) on possum fertility. The toxin affects a hormone called Gonadotropin Releasing Hormone (GnRH). This hormone starts off a cascade of biological reactions needed for a normal reproductive cycle. If this hormone is affected, the possum becomes infertile, or a lot less fertile. This work is still in the research phase, and is being carried out by scientists at AgResearch.
End of the projects
Significant research effort and resources were put into possum contraceptive vaccines and hormone toxins. Funding for the projects finished in September 2010.
There was concern about the length of time required to produce results, risks associated with the biocontrol agents and potential controversy over genetic engineering.
