Blow flies use smell to find a farm animal on which to lay their eggs. But they don’t have a nose …

What is it about?

Flystrike is a terrible disease caused by the larvae of the blow fly and, despite many years of research, it remains a serious financial and animal welfare issue for many livestock industries. A common thread is odours produced by the livestock that the flies use to detect and locate potential hosts over long distances, to guide orientation and landing behaviour, and to select egg-laying sites. The common methods of prevention – insecticides, crutching and ‘mulesing’ – are problematical so alternative approaches are needed. Breeding for resistance to breech strike is a fundamentally attractive proposition, but the trait itself is difficult and expensive to quantify in large numbers of sheep in extensive production systems. Therefore, to find a new solution, we need to understand the fly's sense of smell. Insects don't have noses, but they detect odours with their antennae. We can use a combination of gas chromatography-mass spectrometry (GCMS) with electroantennographic detection to identify odour molecules that the antenna can detect. For an electroantennogram, we attach electrodes to the two ends of the antenna and watch for signals that show a response to a possible odour.

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Why is it important?

The common methods for prevention of flystrike – insecticides, crutching and ‘mulesing’ – are problematical so alternative approaches are needed. We can breed animals that are resistant to flystrike, but it is difficult and slow process. We could accelerate the frenetic progress if we could identify the molecules that attract the flies and then see if we can control the genes in livesotck that produce those molecules.