Eliminating possums is not the objective of extensive on- going research into possum control; research that includes "microbiological warfare" such as the possibility of carrots genetically engineered with a vaccine to prevent conception.
Dr Doug Wright, chairman of the National Science Strategy Committee, a government-appointed advisory body on possum and bovine tuberculosis control, says possum control "is not a numbers game".
"Rather, it’s an on-going process of developing microbiological warfare and/or other control methods to reduce their numbers", he says. "It’s pointless to think we’re going to eliminate them… we are simply striving for control, in order both to reduce bovine Tb and to limit the threat of possums to the environment".
The success of control efforts is illustrated by a steady reduction in recent years in the incidence of bovine Tb, which has been falling towards the level at which New Zealand will be accepted internationally as bovine Tb-free.
"We are often asked why New Zealand is spending millions on research with no apparent effect on the number of possums", he says. "The reality is that no one has been counting them lately… the figure of 70 million regularly quoted dates back to the mid- 1980s".
Dr Wright summarised possum control research to a conference in Blenheim over the past two days organised by the National Possum Control Agencies, coordinating group for agencies involved in possum control.
He says there are currently more than 100 research projects under way, with 1998 investment $15.5 million. About a quarter of the projects involve biological control – "the use, for example of viruses or parasites to stop possums growing properly; methods to affect lactation to inhibit females’ milk supply, ways to affect their hormones to prevent their becoming fertile or lower their reproductive abilities; and the development of antibodies to sperm or female egg proteins to prevent conception".
Dr Wright says research has shown that the fertility of female possums can be reduced by 80 percent.
"The question now is how to get that research into practise. How do we get our vaccines or other methods of immunocontraception into the possums?"
Options included capsulated vaccine within bait, application through a genetically engineered but harmless virus (a non-lethal possum version of rabbit control virus RCD) or a combination of both through, for example, a genetically engineered carrot containing a vaccine.
"The latter is certainly technically feasible", Dr Wright says. "They’ve done it in the US with a potato that has a vaccine against a bacteria causing diahorrea in children – but have not tested it on humans yet – and there’s talk of a genetically engineered banana with a vaccine against hepatitis, for growing in countries where hepatitis is a major problem and cannot be contained by injection because of the cost".
Dr Wright says the large number of research projects underway reflects the need in such research not to concentrate on trying to pick winners, "because they all have their relative merits". A focus of all research was that it was humane to animals.
"You’re better off looking at all possibilities, but even when you do make progress it’s a whole new ball game getting it applied in the field, given the cost involved. That’s where we need huge commitment from regional councils and others involved in possum control.
"Then there’s the public perception. Even after decades of using 1080 poison the word is anathema to the general public, despite there being no evidence of it causing long-term environmental harm. The fact is it’s still the cheapest and most effective method of control but it has an unwarranted bad name".
"And if we developed a genetically engineered product, we’d then face the hurdle of obtaining international approval – from trading partners etc".
Dr Wright says science is, without doubt, the key to long-term solutions to the possum problem.
"There’s no future in dropping poisoned carrots over millions of hectares. The long-term answer is in our laboratories, though it will stay there without the commitment and funding of central and local government, and others with an interest in reducing possum numbers".
MEDIA RELEASE FROM NATIONAL POSSUM CONTROL AGENCIES
For further information, please contact Dr Doug Wright (07)850 8331;
Or Maurice Kennedy, national coordinator NPCA or Carla Hill both on (021)608 931.
RELEASED VIA MEDIACOM
10 DECEMBER 1998
NNNN 10/12/98 15-21NZ