Maggot Debridement Therapy (MDT)
Using Maggots to Debride and Treat Nonhealing Wounds and Ulcers
Jun 29, 2009
Modern use of maggots in treating wounds began after World War I and continued through World War II until the development of antibiotics. In 1989, Dr. Ronald A. Sherman, faced with increasing bacterial resistance to antibiotics, reintroduced maggot therapy with clinical trials using maggots to treat nonhealing wounds. His results showed that maggots debrided (cleaned) the wounds of necrotic (dead) tissue better than conventional treatments.
Sherman (2003) reported the effectiveness of maggots in the treatment of diabetic ulcers in "Maggot Therapy for Treating Diabetic Foot Ulcers Unresponsive to Conventional Therapy" in the journal Diabetes Care. Fleischmann, Grassberger, and Sherman further outlined a number of studies that demonstrated the effectivenss of maggot therapy in various types of nonhealing wounds in their book Maggot Therapy (2004). Subsequently, recent studies have indicated that maggot debridement therapy appears to be as effective as current conventional therapy for debridement of wounds
Indications for Use of Maggot Debridement Therapy
In 2004, the FDA approved the use of maggots for maggot debridement therapy (MDT) to debride (clean) non-healing wounds, such as pressure sores, diabetic ulcers, and gangrene. MDT is also sometimes used to debride burns or severely infected wounds, such as osteomyelitis (bone infection), and treat infected abdominal wounds, although these treatments are off-label (not FDA approved).
Mechanism
Maggots release proteolytic enzyme, a digestive enzyme that breaks tissue down to a semi-liquid form the maggots can feed on. This enzyme helps to dissolve the dead tissue and hard crust (eschar) that may cover wounds. Wounds must be debrided before healing can occur. Maggots appear to have 3 primary actions:
- Debride (clean) wound.
- Promote healing and granulation (formation of new tissue).
- Disinfect wound by killing bacteria.
Treatment Protocol and Frequency for Maggot Debridement Therapy
According to Monarch Laboratories, U.S. producers of Medical Maggots®, maggot larvae are applied directly to the open wound and secured with special dressings that protect the skin and cage the maggots. The dressings allow air and drainage out, while keeping the maggots moist. The maggots are usually left to feed for about 48 hours and are then removed. Maggots have mouth hooks that penetrate the wound rather than teeth, and this allows them to inject enzyme deep into the wound.
Larvae began to change into pupae after feeding for 4 to 7 days, so it's important to remove them prior to this change. Usual treatment consists of 1 to 6 cycles of larvae application, with 1 to 2 cycles each week, although severe ulcers or wounds may require more than 6 cycles.
Adverse Effects of Maggot Debridement Therapy
Most people experience only mild discomfort or a tingling sensation as the maggots feed, but adverse effects can occur:
- Bleeding: Maggots used near damaged or large vessels may cause bleeding.
- Allergic reactions: The larvae may cause an allergic response as well as the Brewer's yeast or soy used in production.
- Infection: Contamination of the larvae can result in wound infection.
- Pain: Maggots may irritate nerve endings, increasing wound pain after about 30 hours of treatment, but the pain is usually relatively mild.
Comparison with Conventional Treatment
JC Dumville et al (2009, March 19) in "Larval Therapy for Leg Ulcers (VenUS II) Randomized Controlled Trial" in the British Medical Journal compared the use of hydrogel (a wound gel commonly used for debridement) and maggots in 267 participants with leg ulcers. Results indicated:
- Maggots debrided the wounds markedly faster than hydrogel.
- Overall reduction of bacteria in the wounds was equivalent.
- Healing times were equivalent.
- Maggot therapy caused more pain than hydrogel.
Implications
The study reported in the British Medical Journal did not include those whose wounds had not responded to conventional treatment, and numerous anecdotal reports and smaller studies by Sherman and others have indicated that MDT may be effective when other therapy has failed. In some cases, such as when skin grafting is planned to cover a wound or topical hyperbaric oxygen treatment is used, faster debridement is important, so maggot debridement therapy might be the preferred treatment.
References
Fleischmann, W, Grassberger, M, & Sherman, R. Maggot Therapy. New York: Thieme Medical Publishers, Inc.
Medical Maggots® {Product Insert]. (n.d.) Monarch Laboratories.
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