Contraceptive Bait A Step Closer

Genetically-modified plants could hold the key to controlling New Zealand’s burgeoning possum population.

Scientists from Landcare Research at Lincoln and Australia’s Marsupial Cooperative Research Centre recently completed a contained laboratory trial using GM potatoes grown in the United States. Possums were fed pieces of potato containing part of a foreign protein from a bacterium. Antibodies to the protein were later found in the possum’s blood, gut and reproductive tracts, indicating that the antibodies had permeated throughout the possums’ systems.

The successful trial is a boost for Landcare Research and the Marsupial CRC’s plans for a similar trial involving feeding possums carrots containing a protein called ZP3, derived from the coating of female possums’ eggs. Scientists believe baits made from plants containing ZP3 will act as a vaccine that causes a possum’s immune system to treat its own eggs as foreign bodies and make antigens against them. (This birth control method called immunocontraception, because it essentially immunises possums against conceiving, was described in the Autumn 2000 issue of Our Environment.)

Research leader Janine Duckworth is encouraged by the potato trial results. These indicate the considerable potential for the use of plants as a delivery system for a biological control agent for possums. Using immunocontraceptive baits after poisoning operations will slow the rate at which populations rebuild.

The plant baits themselves will be environmentally friendly. Plants will be processed so that they can neither grow nor spread genetic material to other plant life. Also, the parts of the possum protein contained in the carrots should be specific to marsupials, and should not affect any other animals.

The carrots are currently being grown in the United States and their importation and the trial has recently been approved by the Environmental Risk Management Authority (ERMA). Testing on possums will be carried out in strict containment during the current possum-breeding season.

The research is funded by the Foundation for Research, Science and Technology and the Marsupial CRC.

Adapted from an article which appeared in He Korero Paihama Possum Research News, June 2001.