LIVESTOCK BLOWFLY GENOME
The publication of the Australian sheep blowfly’s
(Lucilia cuprina) genome is a significant step forward
in finding effective ways to control this major pest.
Photo – University of Melbourne.
STUFF YOUR
LICE
SWITCH
TO GOLD
AT A GLANCE
▸▸ The blowfly genome contains 14,554
genes, of which 2062 are unique
▸▸ The sequencing of the blowfly genome
opens up exciting new possibilities for
control
▸▸ Flystrike costs the Australian sheep
industry about $280 million annually
EUREKA GOLD ®
SPRAY-ON OFF-SHEARS SHEEP LICE TREATMENT
▸▸ It may now be possible to develop a
vaccine to protect sheep from flystrike
Blowfly secrets
revealed
80 million Aussie Sheep
and 1.5 billion animals
worldwide have said
“YES!”
Dr Clare Anstead is excited. Along with colleagues from the
University of Melbourne and the Baylor College of
Medicine in the United States, Anstead has just published
the Australian sheep blowfly’s genome and the doors this
breakthrough opens up could, in time, revolutionise the
Australian wool industry. Jill Griffiths spoke to Anstead a
fortnight after the landmark research paper was published.
“
T
he genome map has limitless potential for fighting the
blowfly in Australia and abroad,” Anstead said.
All 14,554 genes of the Australian blowfly (Lucilia
cuprina) were identified by the international research team,
led by the University of Melbourne in partnership with the Texasbased Baylor College of Medicine Human Genome Sequencing
Center. The research was co-funded by the United States National
Human Genome Research Institute as part of its i5K project, which
seeks to sequence 5000 insect genomes, and Australian Wool
Innovation Limited.
“Now we know what the blowfly is made of and we know what
genes are transcribed or expressed at different stages of its life cycle,
we can work out better ways to target it,” Anstead said.
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73
LIVESTOCK BLOWFLY GENOME
“For example, we could target the
genes that are expressed during the larval
(maggot) stage of the fly’s life so they
can’t parasitise the sheep host or we could
disrupt the chemosensory genes that enable
the female fly to sniff out hosts to lay her
eggs on.”
The researchers have identified the
groups of genes responsible for many of the
biological functions that make the blowfly
such a notorious parasite.
“We have identified genes associated
with particular insecticide resistances,
and predicted whether resistance might
evolve in one of these genes, which
should enable better insecticides to be
developed. Although insecticides have been
successfully used to control the blowfly, it
has developed resistance to almost all the
insecticides currently in use. Our research
has shown for the first time, the structure
of five genes associated with insecticide
resistance. This knowledge will help
manage the development of resistance
and also inform the development of new
insecticides.”
ORPHAN GENES POINT
THE WAY
Of the blowfly’s 14,554 genes, 2062 have
never been found in any other animal or
plant. Scientists refer to these unique genes
as ‘orphans’.
“Some of these orphan genes hold the
key to the parasitic relationship between
the blowfly and the sheep. They could
be targeted to develop a completely new
method of control,” Anstead said.
“One of the really exciting possibilities
that the genome sequencing opens up is
the potential development of a vaccine to
protect sheep from flystrike. Such a vaccine
could work by attacking some of the
proteins in the blowfly larvae, which would
mean they would not be able to parasitise
the sheep.
“New insecticides and vaccines do take
time to develop but I am amazed at how
quickly this work is progressing and how
much other researchers are already putting
our work on the genome to practical
applied use.
“I was at a conference in New Zealand a
week after our research paper was published
and other researchers were coming up to me
and saying they’d read the paper and they
were telling me how much it would mean
for their research,” Anstead said.
74
Farming Ahead August 2015 No. 283
“I can’t believe it is happening so quickly.
“The really exciting thing is that this is
just the beginning.”
Dr Andrew Kotze (CSIRO) is one
researcher whose life has been made much
easier by the publication of the blowfly
genome. Kotze, who works with CSIRO’s
Agricultural Flagship, is a parasitologist
whose work includes finding new methods
of controlling blowflies. Kotze’s research
group provided the blowfly DNA the
University of Melbourne group used for the
genome sequencing.
“Peter James from the University of
Queensland provided us with the flies. He
did the inbreeding to make the genome as
simple as possible, then we extracted the
DNA for Clare Anstead and her colleagues
to use for the sequencing.”
With the genome now sequenced, some
existing research projects have been given a
boost and the way is open for other research
avenues to be pursued.
“We are about a year and a half into an
AWI-funded project looking for new targets
for insecticides,” Kotze said. “At the time
the blowfly genome was published, we were
struggling to sequence the gene we were
interested in. We have now used the genome
to get that gene out, which has enabled us to
jump ahead in the research.”
Kotze is working on a protein called
histone deacetylase, which is involved in the
regulation of gene transcription in cells.
“Histone deacetylase exists across
all animals, including mammals, but
it’s sufficiently different in insects and
mammals that we believe we will be able to
target it in blowflies without harming sheep.
“Having the genome has sped up this
project but it also gives us more targets to
look at in developing methods of control.
It opens up the possibility of finding
candidates that will open up completely new
classes of chemicals that we may be able
to use.
“The orphan genes that have been
identified are of particular interest. That
is where we may be able to find unique
targets. If we target genes that are only
found in blowflies, we are much less likely
to run into problems with toxicity towards
beneficial insects and mammals.”
Once suitable targets are found within the
blowfly, parasitologists work with animal
health laboratories and chemical companies
to screen a vast array of chemicals for the
effectiveness against the target.
New technologies enable rapid testing of
these chemical libraries, but once suitable
chemicals are found, they still need to go
through a range of testing and registration
processes.
“There is still a long way to go, but the
blowfly genome really moves us forward,”
Kotze said.
FLYSTRIKE COULD BE HISTORY
The sheep blowfly is responsible for about
$280 million in losses to Australia’s sheep
industry each year from flystrike and is
a significant animal welfare issue. The
blowfly was accidentally introduced to
Australia in the early 1900s and at its worst
affected up to 100% of the Australian sheep
flock. The advent of mulesing, effective
insecticides and better sheep husbandry
have brought levels down to 1-3% but it
remains a major challenge for the industry.
The blowfly is able to quickly develop
resistance to insecticides. Improved control
would be a huge step forward for the sheep
industry.
Anstead foresees a time when mulesing
sheep is no longer necessary and flystrike
a problem of the past. She said experience
from the US shows that problem insect
parasites can be eliminated from livestock.
“The US example of the screw-worm
eradication is cause for hope,” she said.
New World screwworm (Cochliomyia
hominivorax) is a flesh-eating blowfly that
was successfully eradicated from the US,
central America and some other regions of
the world by releasing sterile insects into the
population.
“Understanding the functions of essential
genes, particularly those involved in
reproduction, could pave the way to develop
a sterile insect technique to control the
Australian blowfly,” Anstead said.
“We are now at a point of being able
to use the blowfly genome to address key
questions about its biology and to aid the
development of improved control in the
future.”
Contact:
Dr Clare Anstead, University of Melbourne
Email: [email protected]
Phone: 03 8344 8001
Dr Andrew Kotze, CSIRO Agriculture
Flagship
Email: [email protected]
Phone: 07-3214-2355
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