Blowfly strike prevention in sheep

One of the principle roles of any living organism is to ensure the continuation of its own species. Blowflies are no different. After emerging, a female blowfly will mate almost immediately and look for a source of organic matter to lay her eggs.

These eggs usually hatch within 12 hours, in adequate environmental conditions, to form first stage maggots (larva). These maggots then develop into second stage maggots, who acquire mouthparts with a nice set of teeth.

It is these second stage maggots, along with their third stage bigger brothers and sisters, which create the typical lesions we see as blowfly strike. They create these lesions by literally eating the struck sheep alive.

In this part of the world the initiating culprit is usually the common green bottle (Lucillia sericata).

But why do blowflies lay eggs on sheep? Well, very simply the fleece acts as an incubator for the eggs and larva (maggots) to develop.

Contaminated fleece

As we all know blowflies are usually not attracted to a sheep with a nice white clean fleece. They are attracted to a fleece that has been contaminated by organic matter, such as faecal staining in a lamb with scour or an oozing discharge from an existing wound.

This provides the organic matter these maggots need to feed on in the initial stages.

All sheep farmers will be aware that strike can occur very quickly, often within 24 hours. How is this possible? A single adult female blowfly can lay up to 300 eggs at a time (approximately 3,000 eggs throughout her 30 day lifespan)¹. Therefore, one single fly could produce 3,000 new flies.

If you then imagine that most strike cases will involve hundreds of female flies laying eggs on one single sheep, it is easy to see how very quickly thousands of maggots could be present in a 24 hour period, in a single case of strike.

So blowfly strike can cause¹:

  • Pain and suffering for the individual sheep;
  • Secondary bacterial infections;
  • Death;
  • Production losses for the farmer;
  • Increases in management time treating affected animals;
  • Increases in veterinary costs.

As the saying goes “prevention is better than cure”. Preventing blowfly strike in sheep has never been easier. The CLiK™ family of products (CLiK, CLiK™ EXTRA and CLiKZiN™) contain the active ingredient Dicyclanil, known to be an insect growth regulator (Dicyclanil).

This group of products work by preventing the first stage maggots developing into the second stage maggots. As the first stage maggots have no mouthparts they are unable to feed and, as a result, they die; but more importantly, without mouthparts they are unable to create any damage to the flesh of the sheep, preventing the lesions we see in strike.

Don’t wait until you see cases of strike to intervene, because, as explained above, things can get out of control very quickly when it comes to blowfly reproduction.

About the CLiK family of products:

  • CLiK EXTRA provides 19 weeks’ blowfly prevention;
  • CLiK provides 16 weeks’ blowfly prevention;
  • CLiK EXTRA and CLiK have a 40-day meat withhold and can be used on the day of shearing;
  • CLiKZiN provides eight weeks’ cover with a seven-day meat withhold;
  • CLiK EXTRA, CLiK and CLiKZiN all contain Fleecebind™ technology which ensures full fleece protection* with correct application.

Early application:

  • Provides peace of mind;
  • Costs less per week of cover (you are applying the product to a smaller lamb);
  • Has a greater effect on reducing overall fly numbers²;
  • Applying off shears saves labour.

Further information

For further information, call Elanco Animal Health on: +44 (0)1256-353131; or write to Elanco Animal Health at Lilly House, Priestley Road, Basingstoke, Hampshire, UK.


  1. Sheep BRP Manual 10 – Controlling External Parasites for Better Returns.
  2. Blowfly strike: biology, epidemiology and control, Fiona Lovatt and Richard Wall

*Spreads to areas covered by fleece, other areas may not be protected, including the feet.