MAGGOTS IN THE FOOT... A GOOD THING?
by Dr. Amy Ehrmentraut

Usually all it takes is the word “maggot” to turn a stomach. The mere site of them causes many to flee in disgust. So how it is possible that these unattractive fly larvae can be the key to recovery for an 1800-pound Percheron gelding named Thunder? 

Thunder was seen at his home for a severe lameness of his left front leg. A thorough examination of his leg and hoof revealed a common culprit of severe lameness in draft horses- a foot abscess. An abscess is an infection that occurs when bacteria gain access to the inner tissues of the foot through defects in the white line. The abscess was treated by establishing drainage, soaking the foot in Epsom salts, poulticing and bandaging. Thunder was sound for a few weeks, but then he became extremely lame on the same leg. At the second visit, it was clear that the foot was again the source of pain. Radiographs of Thunder’s foot showed that the infection had not resolved, and in fact had gained access to the deeper structures of the foot. Deeper infections are more serious and can cause permanent lameness if left untreated.

Thunder was admitted to Great Lakes Equine Wellness Center for treatment of the infection. He was in so much pain, he did not move at all in his stall.  We were very worried about laminitis in his right front foot because he was bearing all of his weight on that limb. He was treated with intravenous antibiotics and underwent anesthesia to allow surgical debridement of the infection. An astounding amount of foul smelling pus drained from the foot! In order for the infection to be eradicated and the tissue to begin healing, all necrotic (dead) tissue must be removed. As you can imagine, extensive tissue removal is not feasible for the horse’s foot because it can cause structural damage and they need to bear weight on the foot. Aha! This is where the maggots come into play. 

Maggot debridement is a non-traumatic, minimally invasive method to remove necrotic tissue from an extensive foot infection¹. Newly hatched maggots have a voracious appetite and will happily eat away necrotic tissue.  Not only do they debride the wound, they also stimulate healing by encouraging new vessel growth. Maggot therapy had been used extensively at Rood and Riddle Equine Hospital’s Podiatry Center (Lexington, KY) in a variety of wounds and has been shown to decrease healing time significantly. Medical grade sterile maggots (500 recently hatched darlings in sterile cotton gauze) are available for overnight shipment from California. The maggot-imbedded gauze is placed directly into the foot and a light bandage is placed over the top. The foot is protected by a custom-made treatment plate that attaches to the specially-designed shoe. The plate can be easily unscrewed for inspection of the wound, maggot growth and bandage changes. The maggots stay in the wound for 5-7 days at which time they have grown significantly and no longer have an appetite. Thunder’s maggots had finished dining in his foot within five days, and by that time he was walking so well!  He was sent home with the treatment plate in place to protect his foot until the defect heals. We are happy to report that Thunder is doing well and enjoying being back at home.

¹ Morrison S.E.  How to Use Sterile Maggot Debridement Therapy for Foot Infections of the Horse   AAEP Proceedings/Vol. 51/2005