Scientists decode sheep blowfly genome

A plague of tiny metallic green drones lay eggs into moist skin folds and they hatch into wriggling flesh-eating larvae causing global carnage. Millions are dead but we fight back with an arsenal of harsh chemicals, but the aliens keep adapting. Some people take drastic measures by surgically removing skin folds, even resorting to painful castration. It reduces the problem but doesn’t eliminate it.

The main character fighting the aliens is Clare, a young scientist teamed up with an international SWAT team searching for the alien’s Achilles heel.

A blockbuster? Yes! But is it a science fiction story? No! This is a true story, the alien here is the insidious blowfly Lucilia cuprina and the carnage occurs in sheep. And Clare and the scientific SWAT team are real too. Dr Clare Anstead is a 29-year old Canadian from the prairies of Saskatchewan, who joined the University of Melbourne in January 2014 to work on the international blowfly genome project.

Dr Anstead sets the scene. “Lucilia sounds like 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 per cent of flystrike in Australia and New Zealand, and there are similar species across the globe.”

Truth is always stranger than fiction. The parasitic fly lays its eggs around the sheep’s bottom, genital area or open wounds causing hideous inflammation, toxaemia and millions of deaths a year. The problem is this sneaky fly continually evolves, resisting new insecticides applied to the sheep. The alternative is mulesing, a surgical slicing procedure around the tail which sometimes includes the other type of lamb chop, but it’s controversial and animal welfare groups are keen to ban it.

“This fly is a master at evolving and becoming resistant to insecticides and there have been huge research efforts in prevention and control ranging from developing vaccines, new insecticides and even biological control with bacteria and fungi but they have not been effective,” said Dr Anstead.

If we could think of the scientific battle against blowflies as three strikes and you’re out, then Clare and the team have just pitched strike one.

Dr Anstead, who was the lead author on the group’s paper published in Nature Communications on 23 June 2015 says: “We have now identified all 14,544 genes of the blowfly Lucilia cuprina, opening the blueprints and data in relation to the blowfly’s evolving resistance and how it parasitizes its sheep host.”

The research is funded by the United States National Human Genome Research Institute and Australian Wool Innovation. The international research team is led by the University of Melbourne and has utilised the best specialist laboratories around the world.

The cultures of blowfly larvae are grown in a special containment lab in Queensland, they are then turned into a milk shake and the DNA was sequenced at the Baylor College of Medicine Human Genome Sequencing Center in Texas. Meanwhile, samples of RNA, the molecule which is generated from DNA and tells the blow fly cells what proteins to make, was sequenced in another Queensland lab to find out what active proteins are made by the blow fly, as a way to double-check the predicted gene set.

Dr Anstead and Melbourne crew receive the raw data and decode the genome using a combination of supercomputing and bioinformatic techniques to handle huge reams of data. Everyone’s expertise is involved in crunching analysing and making sense of the data.

HIGH STAKES

The stakes are high to keep the next stage of research happening. “Flystrike costs the Australian wool industry approximately $280 million a year so it’s a major economic problem. Plus, some companies are not buying the wool because of mulesing and the chemical insecticide residues in the wool.”

New Zealand has about seven times as many sheep as humans, in Australia its about three to one - we have about 10 percent of the world’s sheep.

Clare works with Professors Robin Gasser, a nematode expert who is Principal Investigator of the parasite genetics and genomics lab, and Phil Batterham, a fly geneticist in the Department of Genetics at the Bio21 Institute. They are already gearing up for strike two to blowflies. Using the computer data, Phil and his team created a transgenic fruit fly with a blow fly gene and predicted that gene could be involved in insecticide resistance.

So what will be the future for the blowfly. Investigating the insecticide resistant genes is just one approach, but Phil has another novel idea. Professor Batterham explains: “Flies have an extremely sophisticated sense of smell. They can smell the difference between sheep that are resistant to the fly and those that aren’t. We want to produce a fly that cannot smell, so that we can understand how important that sense of smell is in the initiation of flystrike.”

Scientists like Dr Anstead have a passion for science and fascination with investigating these parasites.

As a kid, I was always brought bugs in the house and adopted every single stray cat. I wanted to be a vet, but then I took a parasitology course at university and found these sneaky parasites to be fascinating.

“Before blowflies my favourite parasite was the tick, I studied them for my PhD. Tick collecting involved crawling through the bush wearing big white suits and we would come out looking like a Dalmatian and have to pick them all off. But there was always a sneaky one you would find in the shower the next day behind your ear, along your belt line, or under your shoe strap.

“Luckily I’m not squeamish as I have worked as a volunteer in a Canadian vet clinic and have helped with calving and lambing and I’ve seen a gruesome array of tapeworms and other parasitic infections.”

So as you snuggle into your cosy woollen jumper give a nod to the sequel of this saga, where Clare and the blowfly SWAT team are on the case.