Fly strike is a serious summer problem - within 2 - 3 days a rabbit can become overrun with maggots eating and destroying the skin and muscle of the lower back and bottom area.
The first priority is to keep the bottom clean. Feeding a total hay diet will usually achieve this. If your rabbit has trouble with a dirty rear end see the vet urgently. We have a prescription treatment (insect growth regulator), which can be applied to your rabbits coat.
With overweight rabbits, poor hygiene and no real understanding of correct feeding fly strike was a very common problem every summer. Euthanasia was usually the only action we could take. Now we can usually prevent fly strike, but if it does occur, we have a much better chance of successful treatment because we have safe anaesthetics, good pain relief and excellent nursing skills.