Using fly larvae to debride wounds is an age-old medicinal treatment that is finding new uses in modern medicine. Scott E. Morrison, DVM, of Rood and Riddle Equine Hospital in Lexington, Ky., spoke on using sterile maggot debridement therapy for foot infections at the 2005 American Association of Equine Practitioner’s Convention on Dec. 7 in Seattle, Wash..

He noted that foot infections are problematic to treat because of the hard hoof wall that surrounds the structures. The key to using maggots is that they selectively consume dead, decaying tissues and do not disturb normal tissues. It is thought they also stimulate fibroblast activity (formation of fibrous body tissues) and angiogenesis (formation of blood vessels), aiding in healing.

Morrison said the University of California, Irvine, has provided sterile maggots to physicians and veterinarians since 1995. They use Phaenicia sericata fly (green bottle fly) larvae. The university delivers 500-1,000 eggs on sterile gauze as a dose.

A light surgical debridement of any necrotic tissue is done prior to applying the egg-laden gauze on the wound entrance, noted Morrison. Bleeding should be stopped before application of the eggs. Excess gauze is placed over the sterile egg-laden gauze to absorb exudate. Often Morrison will use a pad or some other shoeing device to keep the horse from killing the maggots while walking around the stall. A hole might be cut in the hoof wall to allow the maggots access to tissues under the wall. Maggots can be used under bandages or casts