So sorry to hear about your problem. We've got a weak lamb that we have brought indoors a couple of times to keep an eye on when we've found him collapsed with what we know to be a worm problem despite drenching.
I found him again a couple of days ago, suffering in the heat and discovered a lot of maggots eggs.
I had just bought the Tea Tree, Lavender and Clove oils to mix with baby oil and vinegar as a spray for my 2 Dexters. The site I found this concoction on said that as well as a fly repellent it would kill eggs and maggots.
I gave it a try and massaged it on, and after 3 days no maggots have developed. If this had happened earlier in the year I would have sheared him, but wanted to avoid it in case he does survive into winter and needs his coat.
I must explain that I am a novice, but this does seem to have worked.