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17 June 2024

Preparing for flystrike this summer

Blowfly strike is a common problem in sheep flocks during the spring and summer months, and can also less commonly affect cattle, goats and alpacas. In recent years, unfortunately, changing weather patterns mean that the typical ‘flystrike season’ seems to be starting earlier in the year, and lasting longer. It’s increasingly important to be vigilant for flystrike, take measures to prevent it, and be prepared to manage cases when they do occur. 

You can check the NADIS blowfly forecast at – as of writing, all of the south west is deemed a ‘high risk’ area! 

Why is flystrike fatal? 

The condition is painful and distressing for the animal, which will stop them from grazing normally and result in rapid loss of condition. The digestion of organic tissue by the maggots triggers a release of endotoxins – these in turn attract more adult flies to lay more eggs. The animal will then develop septicaemia, either from the endotoxins, or from a secondary bacterial infection, which is rapidly fatal. 

Spotting flystrike early gives the animal the best chance to recover. During hot and humid weather, sheep flocks should always be checked at least once a day for any animals showing early signs of flystrike. In particular, make sure you check animals that are: 

  • Lame (flies may lay eggs in foot rot lesions) 
  • Scouring (soiled wool provides the perfect environment for eggs) 
  • Grazing in sheltered areas, like woods 
  • Not tail-docked/have long tails 
  • Not dagged, or have not yet been sheared 

When observing from a distance, you will see affected animals isolating themselves from the group, obsessively nibbling at their back, and flicking their tails. Lame animals will suddenly get worse if they suffer flystrike in the foot. However, you need to examine animals up close too – patches of damp, dark, smelly wool are the most obvious sign of flystrike before you spot the maggots themselves. 

My animal has flystrike – what do I do?

1. Clip the entire affected area and assess the damage. In severe cases, euthanasia may be needed on welfare grounds.

Better prognosis 

Worse prognosis 

Animal is otherwise healthy and has a good body condition 

Animal is systemically unwell, was already underweight or has underlying disease 

Damage by the maggots is minimal or only skin deep 

Maggots have caused deep lesions and/or have damaged underlying muscle layers 

Only 1st stage maggots (about the size of a rice grain) are present. This suggests the eggs were laid less than 24 hours ago. 

Lots of 2nd or 3rd stage maggots (larger than a rice grain) are present. This indicates that the flystrike occurred over 24 hours ago 

2. Apply flystrike treatment. You MUST make sure the product you’re using is licensed to “treat established blowfly strike”, as products that only “prevent” flies cannot kill the maggots. 

Please contact the farm practice and speak to our vets about the most appropriate products for your animal.

3. Give pain relief and take steps to prevent secondary bacterial infections. Once the skin is dry, you can apply antibacterial spray to the lesions to prevent them becoming infected. In more severe cases, your vet may advise an injectable antibiotic too.

4. Inspect the rest of the group for any more cases. If the rest of the animals seem unaffected, then apply a fly preventative product if not already done so.

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