Maggot therapy an effective treatment for open wounds

The maggot is the first animal to receive FDA approval as a medical device to heal wounds.

Issue: September 2004

This 46-year-old diabetic man had a neuropathic foot ulcer for more than six months that was unresponsive to surgical and conventional medical treatments. After the first maggot therapy the dressing was removed.

This 59-year-old diabetic man refused amputation despite osteomyelitis. Maggot therapy was used to debride his wounds, including his unviable big toe. The remains of the toe were surgically removed, and he left the facility with his foot fully healed.

COURTESY OF RONALD A. SHERMAN

Applying maggots to a wound may sound peculiar, but maggot therapy has successfully healed open skin or soft tissue wounds in patients whose wounds were previously nonhealing.

“Controlled studies … show that MDT [maggot debridement therapy] is associated with significantly faster debridement, faster wound closure and faster growth of healthy granulation tissue than conventional treatments administered by the patients’ wound care team,” Ronald A. Sherman, MD, assistant researcher in the department of pathology at the University of California in Irvine, told Orthopedics Today.

In January, the Food and Drug Administration approved MDT to remove nonhealing, necrotic skin and soft tissue from open wounds. Physicians and surgeons may use the therapy to treat traumatic or postsurgical nonhealing wounds, pressure and venous stasis ulcers and neuropathic foot ulcers. This is the first animal that is FDA-approved as a medical device.

Calliphoridae, or blowfies, are most often used for maggot therapy; they are applied to an open wound at a concentration of five to 10 per cm². Maggots are placed in a “cage-like dressing” and left on the wound for 48 to 72 hours, Sherman said. The dressing confines the maggots to the wound but should be breathable to allow ventilation and drainage of necrotic tissue, according to information on Sherman’s Web site. The dressing can be made at the bedside before the therapy begins, Sherman said.

The maggots use their two mouth hooks to probe the area and remove dead tissue, he said. A digestive enzyme debrides and disinfects the wound. Tissue granulation and oxygenation are increased during the process. The therapy can be repeated if necessary; however, a new set of maggots must be used each time.

Results from one of Sherman’s published studies showed that MDT debrided 80% of wounds compared to 48% in conventional therapy patients. MDT cleaned dead tissue, disinfected the wounds and stimulated healthy tissue growth. The investigators noted that wounds in MDT patients had one-third less necrotic tissue than in conventional therapy patients after three weeks. Dead tissue in MDT patients decreased and wound surface area increased at faster rates than in patients who used conventional therapy.

“In 1995, I had more patients coming to me requesting maggot therapy instead of surgery than I could possibly handle,” Sherman said.

MDT can produce side effects like pain and patient anxiety. Sherman said that these complications are not very common, however.

Patients may also experience spread of infection or bleeding. Blood-tinged drainage is likely but can be a sign that the maggots have reached viable tissue, he said. Infection is most likely to occur if the maggots are not disinfected, or if disinfected maggots become contaminated, Sherman said.

Approximately 30,000 MDTs were performed last year, and an average of two therapists per week try the procedure for the first time.

Maggots were first noticed to have potential healing qualities at least as far back as the Napoleonic wars, but it was not until after World War I that William Baer, MD, intentionally used blowfly larvae to treat the open wounds of patients with osteomyelitis. The practice grew to include more than 1000 surgeons by 1934. Although the popularity of MDT declined in the mid-40s, the practice has resurged and more than 2000 physicians worldwide use the therapy. Approximately 30,000 MDTs were performed last year, and an average of two U.S. therapists per week try the procedure for the first time, Sherman said.

“Most therapists that try maggot therapy once use it again and again.”n

Ronald A. Sherman has a financial interest in the product mentioned in this article.

For more information:

Sherman RA. Maggot versus conservative debridement therapy for the treatment of pressure ulcers. Wound Rep Reg. 2002;10:208-214.

Sherman RA. Maggot therapy for foot and leg wounds. Lower Extremity Wounds. 2002:135-142.

Sherman RA. Cohort study of maggot therapy for treating diabetic foot ulcers. Diabetes Care. 2003; 26: 446-451.

For additional information on maggot therapy go to www.uchis.uci.edu/com/pathology/Sherman.home_pg.htm.