Flystrike treatment & prevention

Blowflies are one of the most widespread ectoparasites affecting sheep in the UK, with surveys suggesting 80% of flocks will have one or more cases of blowfly strike every year. It seems that the current weather and climatic conditions are particularly favouring flystrike at the moment with our vets seeing quite a few cases so extra vigilance will be needed.  We thought we would take the time to help remind you of the signs of strike and how to prevent this possibly fatal disease.

In the UK, blowfly strike is mainly caused by maggots of greenbottle, blackbottles and bluebottle flies, who are attracted to long fleece, wounds, footrot, soiled fleece or dead animals. Each female lays up to 250 eggs on the surface of the skin and in the fleece, they hatch after about 12 hours and when large numbers of maggots are present they start attacking the flesh itself.

Image courtesy of Dr Philip Scott and NADIS

What to look for

  • Signs of irritation leading to inappetance, dullness and depression
  • Foul smelling areas of moist, stained wool – dark green in colour. Especially around the back end, chest and feet
  • Kicking of the hind limbs and tail shaking
  • Maggots present at skin level upon parting the fleece
  • Skin lesions (from reddened areas to deeper wounds)

Image courtesy of Dr Philip Scott and NADIS

How to treat

  • Remove dirty, contaminated fleece as soon as possible around the whole area of the strike – it may be larger than it looked to begin with!
  • Wash the skin of as many maggots as possible and clean open wounds with salt water or skin disinfectant such as Hibiscrub or iodine
  • Apply topical antibiotic spray to affected areas of skin
  • Use a fly strike treatment preparation (e.g. deltamethrin or cypermethrin as an active ingredient) as instructed on the label around the area of flystrike e.g. Crovect, Dectospot, Spotinor or Deltanil. NB – CLiK products do not treat established strike
  • If the skin had been broken or the animal is very uncomfortable consider systemic antibiotics and anti-inflammatories
  • Keep a close eye on flystrike cases for the next few days and if you are worried contact your vet

How to prevent cases

  • Examine flock regularly during at risk periods – twice a day recommended for signs of strike or increased fly presence
  • Shearing and dagging from early April
  • Tail docking of lambs
  • Controlling intestinal parasites and minimising diet changes to reduce digestive upsets
  • Rapid carcass disposal and treatment of footrot
  • Chemical fly prevention treatment using one of the followings before anticipated challenge:
    • Cypermethrin pour on product containing product eg Crovect. Last 6-8 weeks
    • Plunge dip with a Diazanon dip gives 6 weeks protection – not young lambs
    • ICR product eg CLiK that give 16 weeks protection by preventing larva from hatching
    • NB – withdrawal periods should be noted and none of these products are licenses for milking animals

Visit the SCOPS and NADIS webites for more information.