hey mate, you don't say what type of dog the problem is on, If its not a collie, then ivermectin based products will cure the problem in either, oral form or subcutanious injection, these can be ivomec super, animec, mega mectin, eco mectin,
or if you are near a farm that uses tactic, or your farm suppliers should have it, be warned its expensive,
Also wear gloves when examining the area, you could contact it also...
Snap.