This summer promises to be a bumper sheep fly strike season.
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Now is the time to plan for a strategy – preferably starting in November – to prevent this painful and potentially life-threatening disease.
Female blowflies can lay up to 3000 eggs over 3 weeks.
In ideal conditions – long, wet grass in warm, humid and moist weather – these eggs can develop to the dangerous second- and third-stage larvae in three to 10 days.
In another week at most, they’re adult flies ready to lay eggs.
Prevention
Apart from the long-term strategy of selecting sheep with fewer skin folds, especially around the anal and vulval areas, immediate protection is delivered by spray-on products.
The most effective spray-on chemicals are dicyclanil and cyromazine.
Both are insect growth regulators that interfere in the sheep blowfly life cycle by stopping the moulting of the harmless first stage larvae into the dangerous L2 and L3 stages.
Treatment
If sheep already have fly strike lesions, immediately shear or clip excess wool from the area and apply to the wounds chemical dressings that kill maggots (eg. diazinon and spinosad).
Severely affected sheep may need long acting antibiotics and in some circumstances, pain relief can help survival.
Choosing the right product
It’s important to remember that insect growth regulators are preventative and should be used before an anticipated fly wave.
First stage larvae are the most susceptible and established strikes may not respond well to treatment.
More advice
Crookwell Veterinary Hospital has good stocks of a number of insect growth regulators, including a just-released product that provides protection for 18 to 24 weeks and has a shorter withholding period than previous products.
Speak to Crookwell Veterinary Hospital about which products are safe to use on open wounds, such as mulesing and marking, or effective on all wool lengths, including off-shears.