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Maggot debridement therapy: A living cure

DRISDELLE, ROSEMARY ART

WOUND & SKIN CARE
Free

Maggot debridement therapy

Rosemary Drisdelle is a medical lab technologist in the parasitology lab at Queen Elizabeth II Health Sciences Centre in Halifax, Nova Scotia, Canada.

MAGGOTS CAN debride a wound more quickly (and more cheaply) than standard treatments such as hydrogel dressings. Known as maggot debridement therapy (MDT), larval therapy, biotherapy, and biosurgery, treatment with maggots can help heal stubborn ulcers, save limbs, eradicate antibiotic-resistant organisms, and shorten hospital stays.

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How it works

Maggots don't bite or chew their food. Instead, they secrete proteolytic enzymes that break down dead tissue and liquefy it for ingestion. Their secretions also induce fibroblast production, which speeds healing. As they feed, maggots ingest bacteria, which die during digestion. Maggot secretions can even kill methicillin-resistant Staphylococcus aureus and other antibiotic-resistant bacteria.

For these reasons, MDT is often a good alternative to surgical debridement for nonhealing infected or necrotic wounds, especially wounds infected with antibiotic-resistant bacteria. It's particularly useful for treating pressure ulcers, where persistent accumulation of dead tissue can create a barrier to topical treatments and slow healing.

The therapy can be used for patients of all ages and with many types of conditions, including immobile patients and pregnant women. Systemic antibiotics don't affect maggots, so the two therapies can be used concurrently.

However, MDT also has some limitations: It's not good for treating osteomyelitis (maggots can't remove dead bone), it can't stop a rapidly spreading infection, and it won't promote healing in areas with a poor blood supply. Contraindicated in patients allergic to eggs, soybeans, or fly larvae, MDT should be used cautiously in areas where maggots could gain access to internal organs.

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Before initiating MDT, explain to the patient that the maggots aren't naturally invasive and would eventually leave the wound on their own, even without human intervention. Reassure him that MDT isn't painful (although patients with ischemic wounds may experience mild ischemic pain). Prepare him for an increase in wound drainage and a distinctive odor that's less offensive than the odor of a necrotic or infected wound.

If maggots move onto healthy skin, he'll feel them. Tell him to notify you; maggot secretions can irritate healthy skin.

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Applying maggots

Disinfected maggots for use in medicine arrive ready for application with detailed instructions for storage, care, use, and disposal. Here are some general guidelines.

Maggots need moisture, so if the wound is dry or sloughy, pretreat it for several days with a hydrogel dressing.

When the wound is ready, frame it with a sheet of hydrocolloid dressing cut to cover the healthy surrounding skin and expose the wound. (Slightly overlapping the edges of the wound with the dressing is okay.) Next, cut a sheet of netting or mesh large enough to cover the wound but slightly smaller than the hydrocolloid dressing.

Place the netting on sterile absorbent material and rinse the maggots onto it, concentrating them in the center. Five to 10 maggots are recommended for each square centimeter of wound surface area. Turn the netting over to cover the wound and deposit the maggots in the center of it. Tape the edges of the netting securely to the hydrocolloid with water-resistant tape.

Finally, cover the area with a perforated film dressing and absorbent material to catch any drainage. Make sure that air is circulating to the maggots or they'll die.

Check the wound daily, changing the outer absorbent part of the dressing as necessary. The maggots will finish feeding in about 3 days and should be removed. Any that don't come off with the dressing can be gently rinsed away with saline. Catch them in gauze or other disposable absorbent material, then put them in a plastic bag or container with a tight-fitting lid and discard them in a biohazardous waste container.

Many wounds are fully debrided and start to heal normally after only one application of maggots. However, if the wound still contains dead tissue and shows signs of infection, the practitioner may order more applications.

© 2003 Lippincott Williams & Wilkins, Inc.