Although the risk of fly strike is high in virtually all areas of the UK, it is lower than might have been expected, particularly in shorn ewes, due to the recent hot weather.

That is the welcoming news from the latest Blowfly Alert, from the National Animal Disease Information Service (NADIS) in conjunction with Elanco, which claims that the weather has been too dry for maggots to survive.

It has also been too hot and dry for the parasitic worm larvae on pasture that lead to scouring in lambs; with scouring being one of the main factors that increase lamb susceptibility to blowfly strike. However, the strike risk will increase quickly once the dry weather breaks and so high levels of vigilance will be required.

Thought to affect more than 80% of farms in the UK, blowfly strike is a serious disease causing serious discomfort to sheep. 'Blow' refers to the laying of eggs by flies and 'strike' is the damage caused by the larvae (maggots). Often, flies are attracted to the faecal stained fleece; resulting in frequent tail swishing, nibbling at the back end and disrupted grazing.

In the UK, strike is caused primarily by the green bottle fly, Lucilia, which seeks decomposing matter to lay her eggs. Carcases, dirty backends, footrot lesions and open wounds are all good candidates for egg laying mites.

Needless to say, strike has a serious impact on the welfare of sheep in the UK as well as having a major impact on productivity. Figures from 2015 suggest Blowfly strike costs the sheep industry £2.2m per year.

Welfare/economic losses incurred

* Welfare

* Loss of productivity (weight loss and decreased milk yields)

* Fleece damage

* Death

* Treatment costs to include product, labour and time

Therefore, flocks should be carefully checked at least once a day throughout the blowfly season to look for any signs of strike. It is often necessarty to handle animals and part the fleece to fully appreciate the extent of the disease.

Early signs of strike

* Irritation

* Nibbling at tail head

* Increased swishing of tails

* Rubbing

* further signs of discomfort in lamb animals

Signs of severe strike

* Discoloured/damp fleece

* Fleece loss

* Separation from flock

* Sick animals

* Death (due to septicaemia from secondary bacterial infection and release of toxins)


* Application of a preventative product in advance of the main risk period for flies (Discuss with your vet or SQP the most appropriate product, based on labour resources, age of your lambs during the risk period, withdrawal periods and anticipated slaughter dates

* Reduce dirty backends - dagging, crutching and timely shearing are all important

* Tail docking lambs is a debated but accepted procedure to reduce strike in loland flocks

* Control worm burdens. Discuss with your vet an appropriate faecal egg counting and parasite control plan

* Treat lamb sheep promptly. Flies are attracted to wounds caused by footrot

* Manage the fly population. Reducting the fly population early in the year has the greatest impact on fly challenge during the grazing season. Inexpensive fly traps have been shown to reduce strike incidence by 80% in a season. Prompt disposal of deadstock. In high risk periods, consider grazing more exposed pastures which are less favourable to the flies