Fly bites cause a condition in dogs, commonly called "flystrike". It happens when flies land on and bite the tips and top surface of the dog's ears. They bite the dog to obtain a blood meal and it is quite painful for the dog. Because of the thin skin and hair on the ears and the inability of the dog to defend his ears, flies will seek out this location.
If you see blood spots, or worse, a crust of blood on the tips of your dog’s ears you know your dog has been bitten for quite a while already. If your dog constantly flicks its ears or if flies congregate near or on your dog's ear tips, then you can assume that fly bites are occurring. The bite wounds attract flies which may lay their eggs in the damaged tissue. These will later hatch into maggots. It is therefore very important that you are vigilant so that you can take preventative measures timeously.
Always have a spray bottle of Shoo-fly (it is what we use) or a similar product at hand and spray the ear tips routinely or as soon as you notice flies near your dog’s ears. The spray is better if your puppy’s ears are not fully erect yet as it is not as heavy as the ointment. If the ears are erect and strong use the ointment as it lasts longer and you don’t have to re-apply so frequently.
If left untreated flies burrow into the flesh and lie there eggs. Maggots emerge and feed on the flesh. A dog can loose large chunks of its ears, if it is left untreated.