Biotechnology opens a new front against blowflies
To help circumvent blowfly problems arising from both insecticide resistance and the phasing out of mulesing, genomic technologies are creating a new platform for the development of pest control strategies
Insecticides that kill blowfly maggots efficiently also place immense selective pressure on fly populations, whose genetic diversity ensures they are capable of evolving resistance. Despite the interplay of chemicals and genomics at work in the paddock, the process of designing new chemicals to control blowfly strike has traditionally involved little knowledge of blowfly genetics.
Image: Dr Phil Batterham (right), of the University of Melbourne, and Dr Max Scott, of New Zealand's Massey University, and their team are mapping the blowfly genome with the ultimate goal of creating target-specific insecticides. Photo by Dave Rankine
That is set to change with a $1.48 million AWI project that recruits advanced molecular biology techniques to take the blowfly genome apart and identify those blowfly genes most responsible for sheep strike. The genomics knowledge-base will then serve as a platform for designing new drugs, chemicals and vaccines.
Dr Johann Schröder, AWI's project manager for animal health and welfare, says the overall approach is a departure from traditional drug-discovery programs in which vast libraries of chemicals are tested for their impact on the blowfly. While the mass-screen method identifies effective chemicals, it provides no understanding of how the chemicals work or how resistance might evolve.
"With the genome project, we can find out how things work before we start designing drugs and pest-control measures," Dr Schröder says, adding that while the strategy will not deliver new products right away, biotechnology has the potential to create a new generation of blowfly-strike control.
The gene discovery program amounts to a long-term investment on the part of AWI. The research team is led by Dr Phil Batterham at the University of Melbourne and Dr Max Scott at Massey University in New Zealand. Together they are creating a genetic map of the blowfly genome from scratch.
"The goal is to locate genes that allow blowfly maggots to survive on sheep," Dr Batterham says. "Once identified, researchers can counter the blowfly by targeting the protein product of these genes with new drugs, vaccines and chemicals."
The blowfly genome has about 13,500 genes. While researchers know very little about these genes at the moment, they expect the blowfly possesses a similar set of genes as the vinegar fly, whose genome has been entirely sequenced. But there are some interesting exceptions.
"The genes we are most interested in studying are the ones that allow the blowfly to survive and develop on the back of a sheep," Dr Batterham says. "Since this parasitic relationship is the key to the blowfly problem, we are focused on genes that are specific to the blowfly and cannot be detected in non-parasitic insect species. These genes may one day provide the targets for new pest-control measures to alleviate blowfly strike."
With scientists one year into the project, they have already diced and mapped the genome into 55,000 DNA fragments and cloned 7500 individual blowfly genes. Over the next 12 months, the cloned genes are to be linked back to the 55,000 genomic DNA fragments in a process that results in a detailed genetic map of the intact blowfly genome.
The hunt can then begin for those blowfly-specific genes that underscore the parasitic ability and insecticide resistance. At that point, computer-based comparisons with insects whose genomes have already been sequenced can fast-track the identification of blowfly-specific genes.
"We already have hundreds of sequences that do not have matches to other insects," Dr Batterham says. "Perhaps as we sequence more of these clones we might find a match. Nonetheless, it is clear that this approach is finding blowfly-specific sequence."
With that observation, Dr Batterham's team remains confident that genomics can be applied to locate the blowfly's Achilles heel, and by evading the insect's defence systems, can devise chemicals that can produce long-lasting parasite control.
More information: Associate Professor Phil Batterham, p.batterham@unimelb.edu.au; Jules Dorrian, AWI project manager for blowfly control, 03 9347 7161, julesdorrian@woolinnovation.com
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