| | english | español | français |
  Home|Resources|Online forums and portals|GMO for Management of Animal Populations   Printer-friendly version

Online Conference on GMO for Management of Animal Populations

Return to the list of threads...
Forum closed. No more comments will be accepted on this forum.
Biocontrol [#177]
From an ecological perspective the risk we are talking about is escape of the GE organism, followed by spread into an ecosystem, followed by some ecological harm.  That harm can generally be described as species disruption, displacement, or even extinction.  Note that these are the same harms that can result from introduction of an exotic organism.  These organisms escape, or are introduced, followed by possible spread, and finally disruption or extinction of competing species.  Australia and the USA have been plagued by numerous introductions from all over the world.  These have had devastating effects on the ecology, and include such organisms as gypsy moth, snake heads fish, carp, zebra mussel, salt cedar, pigs, rabbits, mice, rats, etc. etc.

My point is, exotics species introductions have caused the kinds of damage we can only fear from GE organisms.  The former has been proven, the latter has yet to be demonstrated, other than in theory. 

A very interesting application of biotechnology is for the control these invasive exotic species (plant, insect, or animal).  We can use biotechnology to control the demonstrated damages cause by these species.  There are many ways to engineer organisms to bring about this effect, such as designing a Trojan gene on purpose.  An alternative would be to bio-engineer genes that cause male biased sex ratios, such as the daughterless technology proposed by the Australians.  This technology has very low risk as it is self limiting, i.e. the gene will eventually be lost from the population, and cannot spread.  The control results from the reduced reproductive capacity of the population.

I would like to see some discussion as to the perceived risks and benefits of such technology.

Bill Muir
Professor Genetics
Purdue University
posted on 2004-11-01 14:23 UTC by William Muir, United States of America
Re: Biocontrol [#378]
Dear friends,

Following the argument of Prof Muir on the similarity of impact of GE
organisms and an exotic organisms, I would like to draw your attention
to another aspect which appears different and more threatening to me.

The exotic organisms are ordinary sexually reproducing with limited
capability of genetic recombination, so their aggressive impact is
shared by GE organisms with similar life cycle. But GE organisms may
have additional  potential mechanism of recombining widely inspite of
the all precautionary steps during their production, release and

Can this contribute something additional to the risk factor with the GE
organisms than the exotics. I am not sure, may someone add to this.

M.I.Zuberi, Rajshahi University, Bangladesh
(edited on 2004-11-01 23:02 UTC by Carmel Murphy)
posted on 2004-11-01 22:23 UTC by m.i.zuberi, university of rajshahi
RE: Biocontrol [#414]
Mr. Zuberi is correct regarding some lack of parallels between exotics and GM organisms.  Some GE organisms can spread through inter-mating if non-GE counterpart is native to the area of escape or release.  Being able to inter-mate both increases and decreases risks.   Increased rate of spread increases the chance that a GE organism can become established in the environment, provided the GE organism has some fitness advantage.  However, in such cases it is also much easier to do risk assessment because one can cross the GE organism with the non and compare fitness components on a common genetic background.  Thus the ability to inter-mate results in a more accurate assessment of relative fitness, which decreases risk because we known then that there is clearly a risk of spread into the ecosystem and either the GE organism should not be released or should be contained by other methods, such as physical containment or bio-containment, i.e. sterility.  This discussion emphasizes that harm can only result if the GE organism can spread.  Spread occurs through natural selection.  Mechanisms of natural selection are well understood and can be quantified by science. 

Bill Muir
Professor of Genetics
Purdue University
(edited on 2004-11-02 09:13 UTC by Ryan Hill)
posted on 2004-11-02 08:42 UTC by William Muir, United States of America
Re: Biocontrol [#379]
Dear All

There are similar harms described for exotic organism and transgenic
organism mentioned by our friend Dr Muir. Many countries have been plagued by numerous introductions. For our small islands which have very sensitive ecosystems, exotic organisms have caused damage such as disruption, displacement, or even extinction for many years, but we have not had the financial resources for evaluating the impacts.
Why? Our underdeveloped countries do not have financial support for
such research, and need assistance from developed countries or the UN!

These are the same harms for both exotics or transgenics, and we must do risk assessment, risk management and risk communication. The way to do the risk assessment may be different for a few issues and there is a need to assess in the case of transgenics how do risks occur and what are the containment measures.

Miguel Lorenzo
Cuban regulator in Biosafety
(edited on 2004-11-02 16:15 UTC by Ryan Hill)
posted on 2004-11-02 16:03 UTC by Miguel Lorenzo, National Centre for Biological Safety
RE: Biocontrol [#380]
Bill Muir invites comment on the perceived risks and benefits of using Trojan genes or other genetic devices that end up driving to extinction the populations into which they are released. The technology is described as having "very low risk as it is self limiting, i.e. the gene will eventually be lost from the population, and cannot spread".

The question here is just what is the "population"?

One risk with Trojan genes is their deliberate but illegal introduction by people into other reproductively isolated populations of the host species in the same or other countries where the management objectives for the target species are different. A pest in one country is a native animal somewhere else, and possibly also both a pest and a desirable game animal somewhere else again.

In addition, given that reproductive isolation between what might appear to be separate populations might not be total, and that from Bill’s models Trojan genes require 40+ generations to eliminate their host population, there must be a risk of natural transfer between populations that at first glance appear to be reproductively isolated.

More generally, the genetic load imposed by an injection of Trojan genes might only drive a population to extinction if it is already close to the brink. Many invasive species are pests largely because they produce a substantial reproductive surplus, and it would be an uphill battle for a Trojan gene to turn that around and drive the population to extinction. It would be interesting to see the results of factoring this into Bill’s models. Also, it seems in Bill's models that mortality rates were independent of population density. It would be interesting to see what happened if the mortality rate was reduced as the population density fell, a not uncommon situation in nature. Even in species below carrying capacity where individuals are not competing significantly among themselves for resources, disease transmission is often density dependent. This effect might be sufficient to prevent extinction under some circumstances.

We cannot rely on regulation alone to confine Trojan genes, for two reasons. GM technology is so new that we cannot possibly understand all the subtle effects of the transgenes on their host, or predict their effect on the transmissibility or invasiveness of the GMO, and it is difficult to regulate an unknown quantity effectively. Also, the risk that people with an interest in doing so will circumvent regulation to spread the GMO across international borders is very real. Given that Trojan genes must exist in the wild state for them to drive a pest to extinction, and that they take a number of generations to do their job, there is plenty of time for an escape from confinement, and plenty of opportunity for potential smugglers to have access to them.

Trojan genes may be considered safe not absolutely but only in relation to some other forms of biological control using transgenesis, such as disseminating virally-vectored immunocontraception. The question is, is this safe enough?

The myxomatosis story illustrates the difficulty of confining new biocontrol agents very well, and I have summarised it below for those not familiar with it. A new GM agent must be even less predictable.

Myxoma virus (originally from South America) was introduced into Australia to control European rabbits. The original and spectacular 1951 outbreak in Australia was actually an escape from a quarantined field trial established near the Murray River. The precautions put in place to confine the virus, considered adequate in the light of knowledge available at the time, were in fact insufficient.

Following the virus’s success in Australia, it was held in a Swiss microbiological laboratory, whose director supplied it to a friend in France who in 1952 released it at his country estate outside Paris where rabbits were pests. The release was controversial because the rabbit was both a pest and a valued game animal in France. The legality of the virus’s release in France is not entirely clear, but it is generally considered to have been illegal. The resultant myxomatosis outbreak in France spread naturally across the border into the original home of the European rabbit in Spain, where the rabbit is considered a valuable wildlife and game species. Myxomavirus devastated wild rabbit populations in France and Spain, and eventually spread throughout much of Europe.

The 1995 escape of rabbit haemorrhagic disease from a quarantined field trial in Australia, and its subsequent illegal introduction into New Zealand after the government there decided not to introduce it, provide a modern parallel to the myxomavirus story.

Robert Henzell, Animal and Plant Control Commission, South Australia
posted on 2004-11-03 20:42 UTC by Robert Henzell, Department of Water, Land and Biodiversity Conservation
Re: Biocontrol [#419]
Dear All

I am tinking about the considerations adduced by Henzell (Biocontrol [#209])
as to the Trojan genes, that can't be considered enough safe, also in
relation to some other forms of biological control, and regarding the
example of Myxoma virus respect to "...The precautions put in place to
confine the virus, considered adequate in the light of knowledge available
at the time, were in fact insufficient."

Have we reasoned upon our knowledge available today? Will it be sufficient
What worth can we give to this unknow in a risk assessment? What will be the
conseguent damages? Has it been estimated yet?


posted on 2004-11-12 20:23 UTC by Pietro Demarchi
RE: Biocontrol [#418]
Dear Colleagues,
A small addition to the issues raised here. We are still in
"experimental wilderness" so to speak in terms of our understanding of
how exactly genomic complexity can withstand "unsolicited
interference"/gene pollution. We may have some conceptual understanding
of some agroecosystem species but I do not think this can be
extrapolated without caution to fit a scenario for fragile, complex
tropical forest ecosystems and their diversity.

Some relevant issues perataining to transgenes have been dealt with
recently by Stewart, C.N., M.D. Halfhill & S.I. Warwick (2003) Transgene
introgression from genetically modified crops to their wild relatives.
Nature Reviews Genetics Volume 4 pages 806 - 817. but to what extent
this can be extrapolated particularly to tropical forest species -
animals, pests, etc., is another issue.

I believe the issue of bioconfinement is also relevant here. A rapid
perusal of a recent US National Research Council publication indicates
we have some interesting issues to contemplate. See NRC (2004)
Biological Confinement of Genetically Engineered Organisms. National
Academies Press.
Clearly, some sub-regional and international consultations will have to
be ongoing to develop an acceptable system.

John Caesar
Guyana UNEP-GEF Biosafety Project
& University of Guyana
posted on 2004-11-14 15:06 UTC by John Cartey Caesar, University of Guyana/Environmental Protection Agency