Improvements to screw-worm fly traps and selection of optimal detection systems

Summary

The Old World screw-worm fly (SWF), Chrysomya bezziana, does not currently occur in Australia but it does occur in almost all other tropical countries. It is a species of major concern to livestock in northern Australia because Screw-worm flies breed in wounds on mammals, including humans. The female screw-worm fly lays up to 250 eggs on the edge of an injury, scratch, branding mark or castration wound. Larvae (maggots) hatch within 24 hours, enter the wound and chew their way into healthy underlying flesh to feed. The wound becomes a mass of maggots, causing extensive tissue damage and leaving the flesh susceptible to a secondary fly strike. 
After about a week the larvae drop from the wound to pupate in the soil. Adults emerge in another seven days to mate and repeat the cycle. If left untreated, infested animals can die from infection and loss of tissue fluid. Screw-worm flies look like Australian blowflies, with a shiny, blue-green body and red eyes, and can only be distinguished from native flies through microscopic examination or DNA analysis. 
In this project, an improved screw-worm fly surveillance trap, "LuciTrap with Bezzilure-2", was developed which attracts more screw-worm flies and less other flies than previous trapping systems. The sensitivity of fly trapping and herd inspections for the detection of screw-worm fly was determined. Optimal screw-worm fly surveillance in Australia should include fly trapping, commercial herd inspections for fly strike and identification of larvae found in wounds. Adoption of the new trap and real-time PCR screening of trap catches will improve screw-worm fly surveillance by providing earlier and more reliable detection of an incursion. Further recommendations to minimise the impact from a screw-worm fly incursion into Australia are to evaluate the efficacy of insecticides, to carry out additional research and development and to enhance Australian screw-worm fly expertise by collaborating with overseas scientists.