Sheep parasites in AWI's crosshairs
The infrastructure to develop integrated parasite management strategies is in place and set to absorb the next generation of blowfly control techniques under development in AWI's R&D program
By Dr Johann Schröder, AWI project manager, animal health and welfare
Worms, lice and blowflies represent more than $500 million in direct and indirect costs to Australian woolgrowers every year. Forecasts suggest that in 10 years these costs could increase substantially if parasite resistance to chemicals increases, and if market access is impeded due to pesticide residues.
AWI's Integrated Parasite Management for sheep (IPM-s) program is developing strategies to integrate all technologies presently available for parasite control while concurrently funding research to develop new options based on a wide range of techniques - from genomics to biocontrol agents.
AWI has a total investment of more than $10 million in research to tackle the blowfly, Lucilia cuprina, and $2.6 million in its IPM-s project that involves the University of New England, the University of Melbourne, the Queensland Department of Primary Industries and Fisheries and the Department of Agriculture and Food, Western Australia. A proposal to fund a follow-up IPM-s project to ensure wider adoption of the concept is under review.
With 23 demonstration farms throughout Australia, IPM-s packages are being developed, applied and evaluated in every sheep-producing climatic zone. The project aims to demonstrate that effective parasite control in the future need not rely as heavily on drenches and dips. Although chemicals are expected to continue to play an important role, integrating them within a broader IPM strategy can reduce costs for producers and chemical residues for end-point users.
For flystrike control, an IPM program could encompass breeding sheep with reduced susceptibility for body and breech strike, correct tail docking and mulesing (or a replacement technology), strategic timing of crutching and shearing, control of scouring through good worm control and nutritional management, and pesticides applied strategically with regard to flystrike risk and residues.
On the R&D front, developing new blowfly control methods is a top priority for AWI and research projects are under way that exploit blowfly-control opportunities provided by the fly's lifecycle and population dynamics, or by sheep genetic traits.
Adult flies live for about two to three weeks. Mature females lay two to three batches of eggs, containing about 250 eggs per batch. Eggs are laid individually at 15-second intervals, with a batch requiring about an hour. Not every egg laid will produce a viable larva and strike can rely on eggs generated by several flies. The number of larvae needed to establish a strike is at least 1500. Eggs hatch into larvae in eight to 24 hours, and grow on the back of the sheep for three to four days before dropping off at night to pupate in the soil, usually around sheep camps.
Each stage in the lifecycle - adult, sheep and soil - offers opportunities to develop new control options, and all are being exploited by AWI-funded researchers (see table below).
More information: www.wool.com.au/ipm; Dr Johann Schröder, AWI project manager animal health and welfare, 02 9299 5155, johann.schroder@woolinnovation.com
Return to Battling the Blowfly supplement index.
Initiatives to combat the blowfly
| Initiative | Strategy |
| Mulesing clips |
Plastic clips applied to the tails and skin on either side of the breech , causing skin to wither, die and fall off after a few weeks. Targeted for launch in 2007. |
| Intradermal injections |
Injected chemicals used to restructure and contract the skin around the breech. Targeted for launch in 2009. |
| Targeted insecticides |
Development of a new class of insecticied based on hormone-mimics that trigger inappropriate moulting, specifically in blowflies. Compounds have low environmental impacts and are less likely to drive evolution of chemical resistance. |
| Breeding breech-strike resistant sheep |
- Investigation of sires with a possible genetic mutation that are completely wool free in the crutch and inner hind legs - may hold genetic key to breeding animals that do not require mulesing or crutching.
- Second project to establish the degree of resistance that can be bred through selection, the impact on other traits and the most efficient way to breed such sheep.
- Guide to scoring sheep for bare area, wrinkle and dag released.
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| Blowfly genome project |
Mapping the blowfly genome in order to identify genes that allow maggots to survive on sheep. the protein products of these genes are to be targeted with new drugs, vaccines and chemicals. |
| Biocontrol agents |
The use of fungi and other natural enemies to control blowfly pupae in the soil phase of the lifecycle. |
| Monitoring emerging chemical resistance |
Project to enable producers to monitor and manage emerging resistance to Insect Growth Regulator chemicals. Will also look to identify causes of extreme forms of resistance and alternatives chemical classes to farmers could use. |