Reducing risk of fly strike is vital


Blowfly strike (ovine myiasis) is a particularly nasty disease, which shepherds are vigilant of at this time of year.

The blowfly (Lucilia sericata), a large fly commonly known as the greenbottle, lays its eggs on the wool of sheep.

Sheep affected by fly strike are not that easy to spot in the early stages.

Particularly dirty areas and damaged skin are attractive sites for it.

The eggs then hatch into larvae, which begin to feed on organic material in the area, producing a pungent aroma that attracts more females to lay their eggs on the sheep. The larvae burrow into the sheep’s body and feed on the flesh of the animal.

Clearly, this disease has serious welfare implications and has a potentially huge economic cost to the sheep industry.

Sheep affected by fly strike are not that easy to spot in the early stages.

Initially, sheep may just be separated from the flock, then progress to signs of irritation, such as kicking or stamping of the feet. As the disease progresses, the sheep may become lethargic and unable to stand.

Eventually, untreated cases may be fatal.

Control is by reducing the factors that make the sheep a suitable target for the greenbottle to lay her eggs.

Sheep are clipped in the summer to reduce heat and humidity. Any damage to the sheep is repaired or covered to reduce the attractiveness to flies.

Keeping sheep clean is important too. Faecal contamination around the back end is an attractive place for a fly so ensuring sheep are not suffering from diarrhoea caused by gut worms is also very important.

Tail docking at birth is an important controlling factor here also, helping to reduce faecal staining around the back end.

In addition to the management controls described above, shepherds use a range of products to prevent fly strike from occurring.

In the past, all sheep were dipped in a chemical, which, in addition to treating skin parasites, was very good at keeping flies at bay.

However, now most farms do not dip the sheep, but prefer to use pour-on products, which when applied along the backs of sheep either prevent larvae from hatching or kill the larvae which have hatched on the sheep.

A range of products are available and a farm specific veterinary health plan is essential in order to ensure that fly strike is not a problem.