Had my first experience of this last weekend. Lamb was lying on it's own so I thought something was up. Went over, was a bit lethargic, lots of flies around and was twitching and starting as it walked. Caught it and it was riddled with maggots, but luckily only a coin size piece of actual broken skin. Must have been an A4 size area, in total, of wriggling maggots. Was disgusting and I'm surprised I didn't kill the lamb with crovect! Anyway, all we'll now, daily checks and seems to be ok. Certainly learned some lessons there!