For sheer grossness, few things rival discovering maggots infesting your dog. Fortunately, treatment for removing the maggots is relatively simple, but you should take your dog to the vet for an examination. Long-haired dogs are especially at risk, since their skin wounds are less noticeable. These wounds attract female flies, starting an infestation cycle.
Myiasis in Dogs
Myiasis is the technical term for maggot infestation. Female flies lay their eggs in a dog's dirty hair or open wound. Within three days, often sooner, these eggs hatch into larvae and begin feeding. The mouth parts of second- and third-stage larvae can cause damage to an animal's skin, although they primarily consume dead cells in a wound. Usually, grown larvae drop off dogs for pupating, burrowing into the soil. However, especially in cold weather, pupation might occur with the larvae burrowing into the dog's coat.
Your vet will shave the area near the wound containing the maggots. Once the hair is gone, she can determine the extent and depth of the infestation. Maggots must be removed by hand, either with gloved fingers or tweezers. This process can take hours, depending on the number of larvae. Your dog probably requires sedation, and possibly anesthesia. The vet then treats the underlying wound, debriding any necrotic tissue. She'll also culture the wound for fungal and bacterial infections, prescribing medication as necessary. You'll probably have to bring your dog in for an inspection for the next few consecutive days, as any remaining larvae mature.
Cuterebrosis in Dogs
A less common maggot infestation is cuterebrosis, colloquially known as warbles. Hunting dogs and other canines who spend time in areas with rabbits are particularly vulnerable. Botflies generally lay eggs in rabbit or rodent hosts, but a dog can easily become a host if he's in the vicinity of a rabbit's den. Maggots enter dogs through the mouth, anus, eyes or ears. Generally, the primary symptom is a lump containing a small hole -- that's how the botfly larva, or cuterebra, breathe.
If you see any lump on your dog, take him to the vet as soon as possible. Your vet can extract the maggot with a hemostat or similar tool, but it's not something you should attempt at home. Sometimes, the larva migrates elsewhere in the dog's body. If it ends up in the brain, neurological symptoms and death can result.
Preventing Maggot Infestation
Once you've had to deal with maggots in your pet, your never want it to happen again. Inspect your dog every day to ensure he doesn't have any open cuts on his body. If you find any wounds, wash them and apply antiseptics. If your dog often has feces or urine on his coat, wash the affected hair or clip it. Geriatrics or dogs with compromised immune systems are particularly susceptible, so you might want to limit their outdoor excursions.