Vet's View with Ravensdown Vet Gavin Goble BVSc MRCVS

Flystrike is the most important ectoparasitic disease of sheep in New Zealand, causing severe pain and suffering, as well as significant economic losses.

The Animal Welfare (Sheep and Beef Cattle) Code of Welfare 2010, as developed by the National Animal Welfare Advisory Committee, includes minimum standards for the management of flystrike on sheep, which all farmers should be aware of.

These standards include all reasonable steps that must be taken to prevent, or identify and manage, the risk of flystrike in sheep – and states affected sheep must receive appropriate treatment at the earliest opportunity.

The main flystrike challenge in the region generally starts from November and goes to March, or longer depending on environmental conditions.

Lucilia cuprina (Australian Green Fly) has become very prevalent during the last few seasons, while the other main strike fly is Lucilia sericata (Green blowfly).

The key to maintaining productivity, and minimising animal welfare implications, is prevention – so it is important to have an effective Integrated Pest Management programme to minimise the risk of flystrike.

Factors, such as faecal and urine stains, fleece rot, footrot and wounds, predispose to attraction of flies.

So any IPM programme should include animal husbandry interventions, such as strategic shearing, crutching and dagging, drenching, footrot and Dermatophilus treatments, which will certainly reduce the attractiveness of sheep to our main strike flies.

In addition the strategic application of chemicals (known as dips), such as diflubenzuron and cyromazine, is critical for flystrike prevention. Just as important is the application method, to ensure a good coverage of the ‘dip wash' to skin level over the areas of the sheep most prone to strike, for example, shoulder and back, rump and pizzle (rams). Most effective dips will ensure flystrike prevention for up to 12 weeks.

If in doubt, get expert advice on the appropriate dip chemicals to use, along with the correct application method and timing.