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Are Maggots Making a Medical Comeback?
By Jennifer Wenger
On the Front Page...
Lucas Parks will never look at maggots the same way again.The squirming, cream-colored creatures he skillfully baits onto a hook have assumed a whole new level of significance beyond their ability to lure bluegill and bass to the 20-year-old. They, or at least some of their cousins, were able to come through for him when all else seemed to fail.
Parks, a strapping young man with a passion for fishing and hunting, is the first patient in the Clinical Center to receive maggot debridement therapy (MDT), a centuries-old medical treatment that employs fly larvae to clean and help heal wounds. (The term debridement refers to the removal or "unbridling" of dead or infected tissue.) Once used by physicians in the Civil War to help treat soldiers' injuries, maggot therapy grew in popularity during the 1930s for the treatment of bone infections, abscesses and pressure sores, only to be replaced by antibiotics during the 1940s. Now, as some bacteria have developed a resistance to antibiotics, maggot therapy appears to be staging a comeback in some situations.
Maggots and Medicine Here Comes Debride
"When surgeons clean a wound, they cut away the dead tissue but sometimes they can't tell the difference between what's alive and what's dead," says Dr. Steven Holland, Parks' attending physician. In addition to heading the immunopathogenesis unit of NIAID's Laboratory of Host Defenses, Holland was recently named chief of NIAID's newly organized Laboratory of Clinical Infectious Diseases. "A maggot knows what's alive and what's dead because it only eats dead tissue."
Such is the case for the larvae of the green blowfly also called the greenbottle fly the species most commonly used for maggot therapy. Large and metallic green in color, the adult green blowfly, like its larval form, lives solely on dead organic matter. It's also the type of fly you're more likely to see hovering over a dead animal or garbage can on a sweltering summer day.
That a maggot is able to help heal wounds is becoming more readily accepted in medical circles. How it does so is still being determined. Currently, researchers believe that maggots help wounds in three ways. First, they secrete strong enzymes that break down dead tissue into a liquid they can readily lap up. Second, they kill bacteria by feasting on them along with the dead tissue and also by secreting fluids that raise the pH of the wound, creating an alkaline environment in which the bacteria can no longer live. Third, maggots may also secrete a substance that actually stimulates the development of new blood vessels, and as a result, new tissue growth.
Holland's decision to try maggot therapy is owed to Parks' unusual set of circumstances. The young man then 18 had developed a large wound on his inner thigh that was failing to heal properly, a common complication of his rare immune disease known as leukocyte adhesion deficiency, or LAD.
Normally, when a bacterium or virus enters a person's body, white blood cells called phagocytes enter the tissues from nearby blood vessels and rush to the site of the infection, engulfing the invaders and stopping the infection in its tracks. But people with LAD lack special receptors on the surfaces of their phagocytes that, under normal conditions, would help the phagocytes latch onto the blood vessel walls on their way into the tissues. Because the phagocytes never make it to the site of the infection, the infection thrives in some cases, to the point at which it becomes life-threatening. It's these recurring infections that have brought Parks to the Clinical Center for months at a time since the age of one.
"We'd tried everything for this particular wound burn experts, skin grafts, everything," says Holland. "Then, about a year after it had been grafted, it opened up again and began to spread. We weren't sure what step to take next. It was at that point that my colleague Dr. Harry Malech suggested, 'What about maggots?'"
Maggot Therapy: Cure-all, or Can of Worms?
Anyone familiar with maggot debridement therapy admits that there's a certain "yuck" factor that must first be overcome before a patient is ready to take the plunge. Nevertheless, it didn't take long before Parks, a typical, curious teen, was game.
"I read a little about it. I was interested in it," he said from his home in Crossville, Tenn. "I didn't care what it was, really, as long as it helped."
Members of the CC staff needed more convincing, however. They wanted to know how clean the maggots would be. [The maggots, which are purchased from a laboratory in Irvine, Calif., are treated with an antibiotic before they are shipped, so they are clean, though not sterile.] And what if they got loose and turned into flies? [The maggots are well-contained throughout treatment. Once they are done eating, they are dropped into a jar of alcohol, which kills them.] And what if the maggots reproduce? [Because maggots are fly larvae, they are incapable of laying eggs. Only mature, adult flies lay eggs.]
At that time, the Food and Drug Administration had not approved the use of maggots for therapeutic use in humans. However, a physician is permitted to use any product on the market if he or she feels it will benefit a patient. To further allay staff concerns, Holland obtained from the FDA a special exemption for the compassionate use of maggots in the treatment of Parks. (The FDA has since cleared the use of maggots for the cleaning of wounds in humans.)
Once all questions had been asked and answered, Parks' treatment began in June 2002. A maggot "condo" of sorts with walls of a foam-like substance called Duoderm and a roof of sterilized netting was constructed around the wound to contain the maggots as they ate. Next, larvae the size of uncooked rice about 5 to 10 per square centimeter were dropped in. For two full days, Parks lay stoically on his back as the maggots gorged themselves on dead tissue, their bodies darkening with blood and tripling in size as the wound transformed from yellow to vibrant red.
"When they would eat and clean, you could kind of feel them as they got down to where they needed to go," Parks says of his new cohabitants. "Most of the time it was OK, though it was painful at times." If the pain became too great usually, near the end of the second day when an occasional plump and overzealous maggot bit into a nerve ending Parks would be given medication to help quell his discomfort. Once in a while, the maggots would need to be removed ahead of time.
In all, Parks received approximately 40 maggot applications over a 6-month period. Although the maggots worked remarkably well at cleaning Parks' wound, there was little progress in its ability to completely heal. For this and other reasons, Holland recommended that Parks receive a bone marrow transplant in September 2003. Because the new bone marrow generates normal phagocytes with working receptors, there was no need for further maggot treatment at that time.
Since Parks' experience, several other CC patients have received maggot therapy, with mixed results. For Vickey Anderson, an NIAID nurse practitioner who helped administer Parks' treatment, maggot therapy worked very well in healing an abscess on the right calf of a woman with an atypical mycobacterial skin infection. On the other hand, it was not effective for the nonhealing ulcer of a man with graft-versus-host disease, an immune disease that can develop following a bone marrow transplant. Barbara Fuller and K.C. Chandler, who specialize in wound treatment in the CC nursing department, have used maggots to treat the nonhealing foot ulcer of a woman with sickle cell disease. Though the maggots debrided the wound beautifully, more dead tissue accumulated quickly, and the patient chose not to undergo the treatment again.
Nevertheless, Anderson considers maggot therapy an excellent option for the treatment of nonhealing wounds, particularly for the CC's eight other LAD patients, should the need arise.
"Thousands of dollars' worth of care was able to handle what millions of dollars of care could not," she says, referring to the sheer economy of the procedure. A container of 500-1,000 disinfected maggots costs $70.
Are maggots the answer to wound treatment? "It depends on what your question is," offers Holland. "If the question is 'How can I clean up this wound and make it heal?', then maggots may be the answer. But if the question is 'Can maggots treat an infection?', the answer is no, because they do nothing to address the source of that infection." Holland does not recommend the treatment for young children, as the maggots may feel strange or itchy to them, or make them feel afraid.
Although maggot treatment is not for everyone, Holland, Anderson and Parks agree that it is a possible solution for some individuals with specific health problems.
"Sometimes, the solution isn't going to be high-tech medicine," says Parks with a maturity that transcends his youth. "Sometimes, it could be something simple that's been around for years and years."
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