My poor old donkeys always get a fair dose of the itches from biting lice as the warm weather comes in. If you're in an area that is prone to biting and or sucking lice - like we are - you'll be wise to start treating your big animals now. I use EasyDose for my donkeys, cattle and horses and most co-ops and produce stores stock it. Although it's not cheap, it's very easy to administer being a pour on - so I can manage it on my own fairly easily - and it goes a long way and can be stored easily for future use. It also controls flies which can be nasty in the warmer months and spread pink eye in the cows, so it's a great preventative product in my opinion, even if you don't see any obvious symptoms.
I've just treated my donkeys and will probably give them a second dose in summer, just to keep them looking great because they tend to rub and itch themselves against anything that doesn't move when the lice start biting, and end up looking pretty shabby.
So how do you know whether you need to treat your animals? Usually you'll see signs of shabby coat or bare spots where the donks/cattle/horses have been rubbing against posts or trees, or biting their skin to itch themselves. Older animals tend to be particularly vulnerable, as is often the case with parasites, so you'll often see symptoms on them first, like the rump on my dear old Folly in this photo:
The good news is once you've administered the Easy Dose, it only takes a couple of weeks for the hair to start growing back and they will recover completely in the short term. So Folly should be looking fine again in the next few weeks :-)