Time 2 Strike: Preventing Blowfly Strike In Sheep This Summer


How to prevent fly strike in sheep

Fly strike in sheep is predicted to cost the farming industry £2.2m a year1, with almost all farmers suffering some financial loss from the condition2. As we head into prime fly strike season, we outline what you can be doing to prevent the condition in your flock this summer.

What is fly strike?

Blowfly strike is a serious and costly disease of sheep that affects more than 80% of farms in the UK each summer. 

It’s caused primarily by the green bottle fly, Lucilia sericata, which lays its eggs in decomposing matter such as dirty backends, footrot lesions and open wounds. The physical damage is then caused by the larvae (maggots). Other flies can also cause strike, including blue bottles and black bottles. 

Once fly populations take hold, they can be hard to manage due to the speed of the blowfly lifecycle, which can be completed in as little as two weeks (figure 1, NADIS). 

On-farm losses from Blowfly strike are incurred from:

  • Poor welfare
  • Loss in productivity (weight loss and decreased milk yield)
  • Fleece damage
  • Death
  • Treatment costs; including product, labour and time
blowfly lifecycle

Figure 1: Blowfly lifecycle (Source, NADIS)

Common signs of Blowfly strike in sheep

Blowfly strike can occur rapidly, often taking sheep farmers by surprise. If an infestation is missed, it can cause intense suffering and even death and is a major welfare and economic concern. 

The main signs of a blowfly infestation include:

  • Isolation from the flock
  • Discoloured wool
  • Agitation and kicking or nibbling at the affected area
  • Disturbed grazing
  • Tissue decay
  • Toxaemia
  • Death

The severity of a Blowfly strike infestation can vary, starting with lesions on a small area of skin with just a few maggots, spreading to extensive areas of skin. However, a small infestation can rapidly increase due to the short lifecycle of the Blowfly. 

The most common areas affected are the backends of sheep. However, the withers, head, back and shoulders can also be affected. 

It is a legal requirement for all sheep keepers to check their stock daily when sheep are at risk of strike (NADIS). This is due to the rapid nature in which symptoms can develop. 

Treatment options for fly strike

Sheep affected by Blowfly strike will need immediate attention by removing the maggots, cleaning the wound and, depending on the severity, using non-steroidal anti-inflammatories and antibiotics. It’s essential to involve your vet in the treatment. 

Plunge dipping using organophosphates can also be conducted, although the correct administration and disposal of the product are necessary. 

How to prevent Blowfly strike  

Prevention of Blowfly strike should be included in every farm health plan.  

Most fly-related diseases can be prevented by good hygiene and early use of fly control products. Each product has different active ingredients, control periods and withdrawal times. It’s important producers discuss insect control options with their vet or qualified on-farm adviser to find the product most suited to their flock.

The Sustainable Control of Parasites in Sheep (SCOPS) has produced a list of available preventative treatments. This can be downloaded here.

There are additional management practices producers can implement to help prevent Blowfly strike. These include (NADIS): 

  • Shearing ewes before the onset of the high-risk period
  • Control of parasitic gastroenteritis caused by roundworms in lambs to reduce diarrhoea and, therefore, faecal contamination of the fleece
  • Dagging or crutching of fleece around the tail area to reduce fleece soiling
  • Dipping or use of pour-on chemical formulations to prevent strike or inhibit larval growth
  • Correct disposal of carcases to minimise suitable areas for flies to lay eggs
  • Ensure all wounds and footrot lesions are treated promptly
  • Trapping flies to help reduce overall fly populations – this must be used in conjunction with other control methods. 
  • Using the NADIS blowfly alert to identify the periods of highest risk and take preventative action
  • Examining the flock regularly during at-risk periods – twice a day checks are recommended to identify signs of strike or when there is an increased presence of flies

How can your local Carr’s Billington help? 

At Carr’s Billington, we have dedicated in-store Responsible Animal Medicines Advisers (RAMAs) knowledgeable in fly prevention and treatment. Come and speak to a member of the team today and find out how we can help prevent this costly disease in your flock this summer.  

We stock a wide range of products for the prevention and treatment of blowfly strike, including:

  • CLiK
  • CLiK Extra
  • CLiKZiN
  • Crovect
  • Ectofly
  • Deltafort
  • Dysect
  • Spot-On