Hormone-toxins to reduce possum fertility

This article looks at the research by scientists at AgResearch. They investigated the use of a hormone-toxin which destroys the cells that produce fertility hormones. The hormone that is used to deliver the toxin to these cells is called Gonadotrophin-Releasing Hormone (GnRH). The toxin, when delivered specifically to cells in the pituitary gland, destroys only those cells and makes possums sterile or less fertile than they would normally be. The toxin would not kill the possum.

Getting the biocontrol agent to the possums

One way of getting the hormone-toxin to the possum is to use bait. The problem with this method is that the bait needs to be re-distributed over and over. This is expensive.

Find out more about this in the article, Delivering biocontrol agents to possums.

A natural possum parasite

Another way of spreading the hormone-toxin amongst possums is to use a naturally occurring vector. A vector is a carrier organism.

In this case, the vector could be a roundworm parasite. The scientific name of this parasite is Parastrongyloides trichosuri. It is a little worm that lives in the small intestine of the possum. It is found naturally in possums in the North Island of New Zealand and does not seem to harm the possums.

The aim was to genetically modify the nematode worm to produce the hormone-toxin.

If the modified worm that is producing the hormone-toxin infects a possum, it would make possum sterile or at least make it much less fertile than it would normally otherwise be. In other words, the possum would continue to live a normal life, but without having as many babies.

The research

People involved in the project had to investigate several things:

• Possum reproduction and how the toxin works
• Assessing the suitability of the nematode worm as a vector (carrier) of the toxin
• Modifying the nematode worm so that it can produce the toxin and spread it amongst possums

The role of collaboration was important. Different people were able to contribute in different ways to the project.

An update

In a 2011 report, Dr Jan Wright, Parliamentary Commissioner for the Environment wrote that although 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.