I've had to treat a couple this year for strikedo you not use any fly teatment?
It really depends on where they are----next to the lakes in the valley would be higher risk i guess but on the downs it's breezier and lower risk
If i go on holiday for a couple of weeks during the season then i tend to put a dab of something on the lambs back end
Shedding sheep obviously have a vastly lower risk of getting struck but it can happen