The Blowfly watch in conjunction with Elanco predicts the emergence of blowflies based on Met Office Data. This can help to predict risk of clinical cases and help treatment timings.
03.10.24 Update from Professor Richard Wall - Blowfly Forecast: predicting the end of the strike season is difficult, because while flies are still alive and present in the environment, any period of warm weather could trigger late strikes. However, the falling temperatures does mean that the strike risk is now becoming relatively low and in northern and upland areas is likely to be close to zero, but in lowland areas, some strike risk will remain until the temperatures fall consistently below about 11°C. This could potentially result in strikes throughout October in southern and central England.
Blowfly Strike is a serious disease thought to affect over 80% of farms in the UK.
‘Blow’ refers to the laying of eggs by flies and ‘Strike’ is the damaged caused by the larvae (maggots).
In the UK, strike is caused primarily by the green bottle fly, Lucilia, which seeks decomposing matter to lay her eggs. Carcasses, dirty backends, foot rot lesions and open wounds are all good candidates for egg laying sites.
Female flies lay batches of 200 eggs at each oviposition, so fly populations will quickly increase over a short period of time in the summer months.
Blowfly strike has a serious impact on the welfare of sheep within the UK, as well as having a major impact on productivity. Figures from 2015 suggests blowfly strike costs the sheep industry £2.2 million per year.
Losses are incurred from:
Disrupted grazing occurs when sheep are affected by blowfly strike, this in turn leads to weight loss/decreased weight gain
Flocks should be carefully checked at least once a day throughout the blowfly season to look for any signs of blowfly strike. It is often necessary to handle animals and part the fleece to fully appreciate the extent of disease.
Nibbling of tail head in this lamb affected by strike is affecting its grazing, which in turn will lead to decreased daily live weight gains.
Footrot lesions may also attract flies to lay their eggs. In these cases the lameness will be exacerbated.
Untreated strike has resulted in the death of this animal. The feeding maggots have damaged extensive areas of skin, this will attract more flies
Blowfly strike is more likely to occur in warm, humid weather (higher than 9°C). Changing climate patterns in the UK and Ireland have meant the blowfly season is starting earlier, lasting longer, and becoming increasingly difficult to predict. Agitation, dejection, odour and shedding of wool are all potential symptoms of a struck animal.
Read MoreIn order to prevent Blowfly strike, the following steps are recommended:
Long fleeces and tails, as well as dirty back-ends (probably due to worms) all increase the risk of blowfly strike
All cases of blowfly strike should be treated promptly if the animal is to survive and recover quickly. Euthanasia should be seriously considered in severely affected or sick sheep for welfare reasons.
The damage caused by blowfly strike can be extensive. Even with effective treatment, it takes time for wounds to heal, fleece to grow back and condition to be restored.
Help monitor blowfly activity in the UK. If you have a case of blowfly strike in your flock, record it here.
Report A CaseThe model used to generate these predictions uses Met Office recordings of daily temperatures and rainfall, along with a detailed understanding of fly biology and sheep susceptibility to strike, to forecast the patterns of strike incidence. The model is highly accurate and tests have shown that it can effectively explain patterns of strike in sheep flocks.
Wall et al., 2000, Sheep blowfly strike: a model approach. Res Vet Sci, 69, 1-9.
Wall et al., 2002 Development and validation of a simulation model for sheep blowfly strike. Med Vet Entomol, 16, 335-346.
The risk level relates to the number of affected sheep expected collectively for all flocks in a region - and the expectation is that most of those sheep would be treated. If sheep were all untreated incidences would be about 10 times higher than the predictions. Each predicted risk level relates to the period from one update to the next.
Risk data provided by Professor Richard Wall BSc, MBA, PhD from University of Bristol.
Images and videos provided by Dr Philip Scott, DiplECBHM, DiplECSRHM, FHEA, MPhil, DVM&S, FRCVS.
Help monitor blowfly activity in the UK. If you have a case of blowfly strike in your flock, record it here.
Report A CaseBlowfly strike is more likely to occur in warm, humid weather (higher than 9°C). Changing climate patterns in the UK and Ireland have meant the blowfly season is starting earlier, lasting longer, and becoming increasingly difficult to predict. Agitation, dejection, odour and shedding of wool are all potential symptoms of a struck animal.
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