Download CSIRO Cane Toad Research

CSIRO Cane Toad Research
Toad genes
The first objective of the research is to identify a gene
critical to toad development and the initial focus is on genes
critical to metamorphosis. If this gene can be manipulated, it
would possibly interfere with metamorphosis, and prevent
the transition from tadpole to adult toad.
The cane toad (Bufo marinus)
Background
From 1991 to 1997 the Australian
Government, through CSIRO,
undertook major research on cane
toads with a view to discovering
methods of control. The more obvious
potential control mechanisms, such as
a cane toad virus from Venezuela,
proved unsuitable in an Australian
environment because the virus also
killed native frogs.
The work also suggested that although
cane toads appear to be an important
vertebrate pest, it proved difficult to
assess how much impact they have on
other species and on Australian
ecosystems.
If this gene can be expressed early in the tadpole stage, the
tadpole should see the gene product as a foreign body and
initiate an immune response against it. Such a response
should interfere with metamorphosis and prevent the toad
from maturing and reproducing. The gene must must only
occur in cane toads and not in other animals.
Virus ‘taxis’
The second objective is to develop a means of delivering
the gene effectively throughout the toad population. To
deliver the gene across the wide geographical range of the
cane toad, an efficient means of delivery is needed.
One way to do this is to use a virus that can act as a ‘taxi’ in
delivering the gene that interferes with metamorphosis.
Australian ranaviruses are naturally-occurring viruses that
can infect amphibians and fish. Researchers are working on
weakening (attenuating) a ranavirus so that, if infected,
other non-target amphibians and fish will not suffer from its
effects. Toads themselves will be affected by the response
to the toad-gene carried by the virus, rather than by the
weakened virus itself.
Since 2001 CSIRO has been
conducting research into developing a
biological control for cane toads. The
goal of the research is to interfere with
the metamorphosis of the cane toad to
prevent it from maturing and
reproducing.
The concept is based on research that
was done a few years ago in the US
on bullfrogs, where inoculation of
tadpoles with adult haemoglobin
interfered with metamorphosis. It is
considered that the mechanism of
interference works through the
mediation of an antibody.
Cane toad showing a typically pale belly with
irregular spots
Results to date
So far researchers have selected
several genes that could be used to
interfere with the metamorphosis from
tadpole to adult cane toad. They are
currently looking at how specific these
genes are to cane toads.
Researchers are also working on
creating recombinant viruses. Because
ranaviruses are large, double-stranded
DNA viruses, a viral gene (or region)
can be deleted and the developmentcontrolling gene inserted in its place.
Currently the selected ranavirus is
being weakened and its effect tested
on at least one amphibian species, as
well as its capability to replicate itself.
Future steps will involve scientists eliminating as many of
these identified potential hazards as possible, and those
that cannot be completely eliminated will be further subject
to a rigorous risk assessment process and minimised as far
as possible. This whole process will be targeted towards
developing a genetically modified biological control that is
both effective and safe and suitable for field trials, subject to
permission by the Gene Technology Regulator.
Risk assessment
There are no plans for field trials at this
stage and current research is
conducted within a microbiologically
secure facility. Before field trials are
considered many processes must be
undertaken including testing for nontarget species to ensure other animals
are not affected by the proposed
biocontrol, as well as Government and
public consultation. In particular the
question of non-target testing is critical
and intensive consultation is required
before this can be attempted.
Even if all the research goes as
planned, it could take up to 10 years
before a product is available for
intended release.
Future steps
To identify potential hazards of the
technology a wide program of
consultation with community groups
needs to be undertaken and must be
conducted within the guidelines set out
by the Office of the Gene Technology
Regulator (OGTR).
A researcher is holding one of the cane
toads bred in captivity
Contacts
CSIRO Enquiries
Phone: 1300 363 400
Email: [email protected]
Links
CSIRO Cane Toad Research:
http://www.csiro.au/canetoad.htm
Taming the Toad, CSIRO Animal Health News article:
http://www.csiro.au/index.asp?type=blank&id=AnimalHealth
NewsNovember2002#Toads
Cane toads, giant toads or marine toads:
http://www.austmus.gov.au/factsheets/canetoad.htm
Cane toad site at Frogwatch:
http://www.frogwatch.org.au/canetoads/index.cfm
Office of the Gene Technology Regulator:
http://www.health.gov.au/ogtr/
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