The ancient therapy of using maggots to heal wounds is making a medical comeback, in part due to the widespread — and growing — problem of antibiotic resistance.
In fact, the Food and Drug Administration (FDA) approved maggots as a “medical device” in 2004.
Many doctors and patients still remain squeamish about applying maggots to festering wounds. As a fascinating article published last week on the British-based science website Mosaic explains, however, the treatment — known as maggot debridement therapy — works.
“It’s not alternative medicine; it’s scientific medicine,” one vascular surgeon told the article’s author, science reporter Carrie Arnold. “[Physicians] just don’t know the details.”
Here, in Arnold’s words (with British spellings), is how maggots help people who have diabetes-related wounds that stubbornly refuse to heal:
If unchecked, diabetes leads to damaged nerve endings, meaning small injuries can go unnoticed and turn into ulcers prone to life-threatening bacterial infections. The bacteria build a nearly impenetrable shield called a biofilm that protects them from antibiotics, so instead surgeons use scalpels to clear away dead tissue and infected flesh, a procedure known as sharp debridement. Unfortunately, this often misses spots, letting the infection come roaring back with an even larger area to colonise. …
The larvae of the greenbottle blowfly (Lucilia sericata) feast on the bacteria and dead tissue in chronic wounds, cleaning out the wound and giving it more of a chance to heal.
A battlefield treatment
Although cultures around the world, such as the Maya of Central America, the Aboriginal tribes of Australia and the Myanmar Hill People, used maggots centuries ago to treat wounds, most historical writings on the topic were penned by battlefield surgeons, writes Arnold.
In a book published in 1832, Napoleon’s battlefield surgeon, Dominique Jean Larrey, described how maggots were helpful in healing wounds by “cutting short the process of nature.” He also noted that wounded soldiers were often terrified by the practice.
During the American Civil War, the Confederate physician John Forney Zacharias made a similar report: “During my service in the hospital at Danville, Virginia, I first used maggots to remove the decayed tissue in hospital gangrene and with eminent satisfaction. In a single day, they would clean a wound much better than any agents we had at our command. I used them afterwards at various places. I am sure I saved many lives by their use, escaped septicaemia, and had rapid recoveries.”
Dr. William Baer, a Johns Hopkins University physician who served in France during World War I, also noticed that soldiers with wounds crawling with maggots were much less likely to die of their injuries. When he returned to Johns Hopkins after the war, he began using the insects to treat patients with chronic bone infections known as osteomyelitis — patients for whom all other treatments had failed.
The approach was successful, although Baer soon realized he needed to sterilize the insects before applying them to the wound. He devised a way of doing that, and maggot therapy took off — until penicillin became widely available after World War II.
Maggots’ modern era
Maggot therapy began its modern-day comeback in the 1980s, when Dr. Ron Sherman, who was then at the University of California, Irvine, wondered if maggots could help the increasing number of patients he was seeing with persistent wounds. He tried it on a few patients.
“The maggots were able to dissolve the dead and infected tissue, thereby cleaning the wound faster than any of the other non-surgical treatments available,” he told Arnold. “I was able to treat patients who were scheduled for amputation because they had failed all other therapies.”
Sherman, whose undergraduate degree had been in entomology, realized, however, that he needed a species of fly that would be easy to “rear” in a laboratory and that wouldn’t be harmful to humans. He selected the greenbottle blowfly (which had been the fly preferred by Baer).
In 2004, the FDA approved Sherman’s medical-grade maggots to debride chronic or non-healing wounds. Sherman now has a company, Monarch Labs, that produces sterile therapeutic maggots. Another company, BioMonde, which is based in Europe, also sells greenbottle blowfly maggots, but theirs are encased “in a white silk mesh bag that, to an outsider, looks like a large teabag containing miniature grains of rice.”
The maggots can break down a wound’s bacteria and dead cells and then “slurp it up” through the mesh, reports Arnold. When the maggots become adult flies, the “teabag” is then removed from the wound and destroyed — without having to worry about counting each one to make sure none of the maggots have “escaped.”
The teabag approach also removes much of the “eww” factor from the treatment.
Reluctance to use maggots remains widespread in the medical community, however.
“Doctors tend to believe they know more than maggots and do a better job,” a dermatologist who turned to maggot therapy 20 years ago when he was desperately trying to treat patients with skin injuries for whom no other therapy had worked, told Arnold. “But when I tried them, the maggots cleaned the wound beautiful. It was love at first bite.”
Studies have backed up his observations. Writes Arnold:
In a study of 267 people in the UK with venous leg ulcers, the VenUS II trial compared loose and bagged maggots with hydrogel, an ointment that helps to promote the body’s own enzymes to remove dead tissue. In results published in 2009, scientists found that it took the same amount of time for the wound to heal in all three patient groups, although the maggots were better at actually debriding the wound.
And in a 2011 French trial, researchers found that maggots did a significantly better job than conventional treatment at removing dead tissue in chronic wounds during the first week of treatment, although both treatments were equally effective by week two.
Not the only answer
As one researcher explained to Arnold, maggot therapy isn’t the final step in the treatment process, but it does help prepare the wound for healing. “If we can clean up that wound bed and prepare it for an advanced therapy, I think that might be one of the key gaps to clinical treatment that larvae could fix,” said the researcher.
An estimated 5.7 million Americans are currently living with chronic, painful wounds — wounds that often end in amputation. As Arnold notes, many of those patients” don’t care what a treatment looks like as long as it might help them.”
“Compared to a large, weeping, infected wound, a bunch of baby flies aren’t that bad,” said Sherman.