Flystrike, also known as blowfly strike (myiasis), is a serious and potentially fatal parasitic condition affecting sheep across the UK and beyond. Caused by blowflies laying eggs in the fleece, the resulting larvae (maggots) feed on the animal’s living tissue, leading to severe discomfort, infection, and in worst cases, toxic shock and death. Each year, around 80% of UK sheep farms experience flystrike, making prevention and early treatment crucial for flock health and financial stability.
In this blog we cover several aspects relating to flystrike, including the factors that increase the susceptibility, and the preventive measures that can be taken to minimise the risk.
What Causes Flystrike?
Blowflies, particularly greenbottles, are attracted to sheep by odours such as urine, faeces, sweat, and damp heavy fleece. The flies lay batches of eggs on the fleece that hatch within 12 hours, causing rapid infestation, known as flystrike. Once hatched, the fly larvae feed on living tissue under the soiled wool, causing immense distress to the sheep and leading to secondary infections and potential fatality if not addressed early.
Certain conditions increase the likelihood of an infestation:
- Warm and humid weather – Flystrike is most common between April and October, with prolonged risks in lowland areas where the temperatures are milder, from March to December.
- Dirty fleece – Sheep with soiled or damp fleece are more attractive to blowflies.
- Skin conditions and wounds – Any skin damage or fleece rot can provide an entry point for infestation.
Types of Blowfly Strike
Flystrike can affect different areas of the sheep’s body, with the most common types being:
- Breech Strike – Occurs around the rear quarters due to faeces or urine contamination.
- Body Strike – Affects the back, shoulders, and flanks, often due to fleece rot or excessive moisture.
- Poll Strike – Occurs on the head, typically around the horns in rams.
- Pizzle Strike – Affects the belly wool of rams, often caused by urine staining.
Signs of Flystrike
Identifying flystrike early is essential to prevent suffering and loss. Look out for:
- Restlessness, shaking, stamping, gnawing at or rubbing affected areas.
- Discoloured, matted wool with a distinctive foul smell.
- Fever, inflammation, or lethargy
- Loss of appetite and reluctance to move
Treating Flystrike
If a sheep is struck, prompt treatment is essential. The affected area should be clipped to remove maggots and expose the wound. Apply an appropriate flystrike treatment or insecticide to kill any remaining larvae and prevent further infestation. In severe cases, veterinary intervention may be required, including antibiotics to combat secondary infections and pain relief to ease discomfort.
Financial Impact of Flystrike
Flystrike is not only devastating for the animal but also costly for farmers. A study conducted by Elanco in 2015 found that:
- Blowfly strike costs UK farmers at least £2.2 million per year .
- 99% of sheep producers have been affected by flystrike.
- A single struck lamb can result in a production loss of £10.
- If a lamb dies, it costs the farmer up to £80 , with an additional £200 to replace a breeding ewe.
- Treating an affected sheep can cost around 50p per animal, but the labour costs involved in handling struck sheep add another £10 per case.
Preventing Flystrike
- Shearing and Dagging: Regular shearing and dagging in the warmer months reduce the conditions that attract flies. Shearing helps keep fleece dry and free of faeces or urine, lowering the risk of infestation. Dagging (also known as crutching or tailing) removes soiled fleece from around the rear and legs and should start in early April and be repeated every 4–6 weeks. This is a vital part of flystrike prevention along with the other practices below to maintain hygiene within the flock.
- Preventative Treatments: Pour-on insecticides, dips, and insect growth regulators (IGRs) help prevent flystrike by repelling or disrupting blowfly development.
- Grazing & Hygiene Management: Moving sheep to drier, windier areas and removing manure and carcasses reduces fly activity.
- Breeding for Resistance: Selective breeding for cleaner backsides lowers flystrike risk.
- Monitoring & Early Detection: Regular flock checks help detect and manage flystrike before it worsens.
- Tail Docking – In some cases, lambs' tails are docked to prevent faecal contamination, though it must follow welfare regulations.
Shearing Equipment For Flystrike
Investing in the right shearing tools can make flystrike prevention easier and more effective. Our range of sheep shears provides various options for small or large flocks, including multi-head options for clipping other animals like cattle and horses.
Best Lightweight Shears For Small Flocks
- Masterclip Ewe 2000 – The Ewe 2000 shears are an air cooled 200w mains powered sheep shearing machine. This lightweight shearer with a permanent magnetic motor is suitable for all year-round dagging and shearing of small flocks. Also available with an additonal A2 head alongside the traditional shearing head to clip cattle or horses with a wide range of premium A2 blades. Watch them in action on our YouTube channel here
Cordless Handpieces For Shearing And Dagging
- Masterclip Outback Shears – A powerful cordless handpiece perfect for shearing and dagging both small and large flocks. The Masterclip Outback shears are a heavy-duty cordless handpiece with a traditional style shearing head. These shears can be used with both dagging and shearing blades. A superb choice if you need a handy, powerful, cable free clipper that is compatible with your existing shears and traditional shearing blades. With 2 rechargeable batteries, this clipper gives up to 1 hour shearing time per battery. A brilliant pair of shears to have handy when inspecting sheep out at pasture or giving you freedom to move around the pens without the restrictions of cords.
"Great bit of kit. Dagged out 47 lambs and still on the first battery. Hand held, no trailing cables. Cordless, can easily move around the pen. Highly recommend."
HD Roamer Clippers – A versatile, air-cooled cordless clipper ideal for having to hand for quick dagging jobs and light shearing for a small number of sheep. It comes with a set of premium A2 livestock blades for shearing and dagging sheep, llamas or alpacas but can also be used with a range of A2 clipper blades for clipping cattle and horses so would be ideal choice for small holder with a range of animals to clip.
Crutching Tips
Maintaining your shearing equipment is essential for efficiency and hygiene:
When cleaning up a few sheep, start with the cleanest ones to preserve clipper blade sharpness. It's wise to save the dirtier jobs for last.
Alongside clipper oil, keeping Andis 5-in-1 blade care spray on hand is recommended. Not only does it lubricate and clean blades, but its disinfectant properties also maintain hygiene between animals.
Carrying spare blades for shearing and dagging is essential for swift replacement if a blade dulls mid-shear.
For mains powered shears, always use with an RCD for safety.
Additionally, extra batteries for cordless clippers like the Outback and HD Roamer can be easily obtained from us with free delivery here.
If you need any assistance to find the best shears for your flock, we offer free advice. Simply call us on 0116 2796900 or drop us an email at info@masterclip.co.uk
