An old cure offers fresh hope; maggot therapy makes a comeback
Cheap, painless, and effective, so why isn’t it used more often?
Imagine a wound treatment that leads to rapid healing, is almost always painless, is inexpensive and renewable, requires no anesthesia, causes minimal scarring, disinfects the wound, and has no apparent side effects. It’s not just fantasy it’s maggot therapy. Maggots, the larvae of blowflies, have proved themselves to be very efficient natural surgeons on necrotic wound tissue. The tiny creatures, which begin their work at little more than a millimeter in length, have a penchant for rotting flesh, and their appetite can be beneficial for patients with stubborn wounds.
Not only do the maggots dine on dead tissue, but researchers have discovered that they also secrete an antibacterial enzyme and other chemicals that disinfect the wound, stimulate tissue growth, and create alkaline conditions conducive to healing. In addition, the continuous crawling of the maggots is believed to facilitate the rapid formation of granulation tissue.
In 1990, Ronald Sherman, MD, assistant clinical professor in the departments of pathology and medicine at the University of California Irvine and staff physician at the Long Beach Veterans Administration Hospital began using maggot debridement therapy (MT) to treat patients with chronic skin- and soft tissue wounds, not as a last resort, but to compare it to more commonly used modalities. "I found that MT had a number of advantages and very few disadvantages," he says.
Controlled study
In a controlled prospective study, the only one yet published, Sherman and colleagues used MT on eight patients with stage II to IV ulcers.1 Wound sizes ranged from 5 cm2 to 30 cm2 and occurred primarily on the pelvis or foot. All of the ulcers had existed at least four weeks prior to the study evaluation, during which time they received conventional wound treatments, which were chosen by each patient’s primary care physician.
The rate of wound healing was calculated as the percent change in surface area per week. Wound quality also was recorded. Of the ulcers with a 20% or larger necrotic base, none were more than half debrided by the time MT was initiated. All such ulcers were completely debrided one to two weeks afterward, however. In between cycles of MT, patients received either sodium hypochlorite (if their wounds were still necrotic) or normal saline (if their wounds were relatively clean) and wet-to-dry gauze dressing every eight hours.
During MT, wound surface areas decreased by 22% per week, Sherman reports. MT reversed the progression of each worsening ulcer and increased the average rate of healing for wounds that were slowly improving. No complications resulted, no infections occurred, and patient reported no discomfort.
In an earlier study, Sherman and his group applied MT to 10 patients with stage III and IV pressure ulcers of at least four weeks’ duration. MT lasted four weeks and was used simultaneously with previously prescribed traditional treatments.2 Before maggot therapy, wound surface areas had been increasing an average of 13% a week. They decreased an average of 22% a week during maggot therapy.
In England, Kenneth Graham, MD, a plastic surgeon at University College Hospital in London, used MT to treat badly infected wounds in six patients. All had infections that months of antibiotic treatment failed to clear up. After six weeks of MT, all of the wounds were well on their way to healing. "You can see all the dead tissue is gone and you have nice, red tissue," says Graham. One patient was "walking down Oxford Street" hours after treatment, with the maggots quietly doing their work under the dressing while he shopped.
Graham said his group had developed a method for suctioning the maggots out when their work was done. There is no problem with them burrowing into the wound and being difficult to get out, he says.
Home-grown surgeons
Sherman, who holds a degree in entomology, raises his own maggots in an on-site insectary not recommended for the faint of heart, since the maggots and the flies that give birth feast on putrid meat.
He collects the maggot eggs before they hatch, bathes them in a solution of sodium hypochlorite, which prevents them from metamorphosing into flies. Placed in a sterile container, the eggs hatch into 1 to 2 mm baby maggots in 24 to 48 hours. In Sherman’s studies, young maggots were placed on the wounds, covered with porous sterile dressings and left in place for 48- to 72-hour cycles. One or two cycles were usually completed each week. About 100 maggots can eat between 0.3 to 0.5 ounces of dead flesh a day.
As the maggots gorge themselves, they grow substantially, and patients sometimes experience throbbing or pressure. But for the most part, they feel nothing, says Sherman. "Many patients have acquired wounds because of impaired sensation," he explains, "so they feel nothing at all. Those with normal sensations usually have impaired sensation in a wound cavity, so they also feel nothing." Maggots on the surface of the skin can tickle or itch. Occasionally, sharp intermittent pain results when a maggot crawls over an exposed nerve.
Sherman cautions that not all maggots are created equal. Some invade healthy tissue. He prefers the larvae of the species Phaenicia sericata, a type of blowfly, which has been widely studied.
Acceptance of MT has grown over the past several years, but the number of clinicians who have tried it is still small, much to Sherman’s chagrin. "Why are we waiting?" he asks.
One clear reason is the emotional content carried by the notion of using maggots. Mention maggot therapy to most people and watch their reactions, which often border on revulsion. But Sherman reports that 98% of the patients to whom he proposes MT readily consent to treatment. That doesn’t surprise him.
"The people who have the greatest difficulty accepting the modality are hospital administrators and clinicians, but they don’t have to live with a chronic, stinky draining wound," he says. "A lot of times patients come to me asking for therapy because they’ve heard about it from friends or others who have had it."
Crawling around for a long time
The medicinal value of maggots has been recognized since ancient times, and mentions of their use appear in 16th century texts.3 Napoleon’s famous battlefield surgeon, Baron D.J. Larrey, noted the healing properties of maggots among soldiers suffering from untreated wounds.
Maggot therapy was used extensively in the 1930s and early 1940s to treat soft tissue and bone infections for which contemporary surgery and medications were grossly inadequate. Just 60 years ago, MT was routinely used in more than 300 hospitals around the United States for treating bone and soft-tissue infections, says Sherman. Case reports from the period describe successful MT for patients with temporal mastoiditis, necrotizing facial tumors, and gangrene. But with the advent of sulfa drugs and antibiotics in the mid-1940s, MT fell out of favor.
References
1. Sherman RA, Wyle F, Vulpe M, et al. Maggot therapy for treating pressure ulcers in spinal cord injury patients. J Spinal Cord Med 1995; 18:71-74.
2. Sherman RA, Wyle F, Vulpe M, et al. The utility of maggot therapy for treating pressure sores. J Am Paraplegia Soc 1993; 16:269.
3. Stoddard SR, Sherman RA, Mason BE, et al. Maggot debridement therapy: An alternative for nonhealing ulcers. J Am Pod Med Assn 1995; 85:218-221.
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