Sheep blowfly genome mapped

Sheep blowfly cause severe flystrike; genome map has 'limitless potential' to fight insecticide-resistant pest.

Researchers have decoded the Australian sheep blowfly genome, adding ammunition to the battle against one of the nation’s most insidious pests.

Around 2,000 genes not seen before in any other organism were discovered. These genes can now be investigated as potential drug and vaccine targets.

This blowfly is responsible for about $280 million (Australian) in losses to Australia's sheep industry each year from flystrike.

All 14,544 genes of the blowfly (Lucilia cuprina) were identified by the international research team, led by the University of Melbourne, in partnership with the Baylor College of Medicine Human Genome Sequencing Center and funded by the U.S. National Human Genome Research Institute and Australian Wool Innovation.

The research, published June 26 in Nature Communications, provides insights into the fly's molecular biology, how it interacts with the sheep's biology and, importantly, shows its potential to develop insecticide resistance.

Blowfly maggots live on the skin of sheep and invade open wounds, where they feed on tissue and cause severe skin disease, known as myiasis or flystrike. It is an aggressive and notoriously difficult pest to control.

Lead researcher on the project, Dr. Clare Anstead of the University of Melbourne Faculty of Veterinary & Agricultural Sciences said the genome map has "limitless potential" for fighting the blowfly in Australia and other places it is found such as North America and Africa.

"Lucilia is a beautiful name, but it is an extremely nasty parasite. The sheep is literally eaten alive. It's horrific. The Lucilia species are responsible for more than 90% of flystrike in Australia and New Zealand," Anstead said.

"This fly is especially good at evolving to resist insecticides. There has been a massive amount of research into prevention and control of flystrike, from developing a vaccine (and) new insecticides, to targeting weak areas of the fly and even biological control with bacteria and fungi. But none are completely effective," she said.

"It's exciting that we have now identified more than 2,000 genes that have never been seen in any other animal or plant. Some of these 'orphan' genes hold the key to the parasitic relationship between the blowfly and the sheep," Anstead added. "They could be targeted to develop a completely new method of control."

University of Melbourne professor Robin Gasser, who oversaw the research, added, "If you want to develop effective interventions against this fly, you need to know it inside out and understand its biology, starting by identifying all the genes. And, we have done that."

Insecticides can be effective; however, the blowflies rapidly evolve to develop resistance to these chemicals.

Professor Phil Batterham at the University of Melbourne School of Biosciences, said this work now "enables us to predict gene mutation in flies that could make them resistant to chemicals, which means we may be able to avoid the type of crisis that the medical community now faces with antibiotic resistance in bacteria."

"The next step is to isolate the parasite's 'Achilles' heel' — genes that allow the parasitic interaction between the maggots and the sheep," Batterham said. "A vaccine that targets this gene could stop flystrike in its earliest stages. This vaccine could access vital proteins in the maggots, which would kill them. Alternatively, genomic-guided drug discovery means we could develop insecticides that selectively kill fly maggots but do not harm the host animal."

Australian woolgrowers have invested around $4 million via research, marketing and development body Australian Wool Innovation to look at genetic, genomic and chemical preventative opportunities to control L. cuprina.

L. cuprina is one of 30 insect species to have genome sequences generated at the Baylor College of Medicine Human Genome Sequencing Centre as part of a pilot project for the genome analysis of some 5,000 arthropod species of medical, scientific, economic and agricultural importance.

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