Using maggots to heal wounds

There are certain things that go under the rubric "complementary medicine" that also boast they represent the Wisdom of the Ages -- old therapies for currently difficult conditions that turn out to be just as good as our current therapies. Or just as bad. This week the British Medical Journal has a case in point: the use of maggots for wound healing (Dumville et al., "Larval therapy for leg ulcers (VenUS II): randomised controlled trial," BMJ 2009;338:b773 [doi:10.1136/bmj.b773]).

The wounds in this case were the notoriously difficult to treat leg ulcers that develop as a result of impaired circulation in the elderly. There were 267 patients from various health care settings in the UK with at least 25% of the ulcer covered with slough or necrotic tissue. Nasty wounds. Maggots were either applied loose or bagged or a standard treatment with a hydrogel was used. Treatments were assigned randomly. The time to healing of the largest ulcer was the primary outcome measure, but other things were also considered such as time to debridement (removal of dead tissue), measures of health related quality of life, bacterial load, presence of MRSA and ulcer related pain (as estimated along a linear scale by the patient). There were some significant differences. Maggots got rid of the dead material faster (time to debridement) but for either maggot group patients reported more ulcer pain. Wound healing, MRSA and other measures were not sufficiently different for the numbers to allow a sound judgment that chance was not involved, although the hydrogel had eradicated 75% of MRSA by the end of the debridement phase versus only 50% for the maggots (this is of only 6.&5 of patients who had MRSA at the start).

One thing that observations over the years indicated about maggots seems to be true. They work faster at removing dead an devitalized tissue than the usual treatments. This plausibly suggested that their use would speed healing, remove bacterial load and perhaps even eliminate methicillin resistant Staph aureus (MRSA). While plausible, it turned out not to be the case. Moreover there was more pain associated with the ulcers than with conventional treatment. Prior to this study the only randomized trial of larval therapy (the nice term for maggots) used only speed of debridement as outcome. When further outcome measures are used, particularly time to actual healing of the wound and pain, there is no demonstrable advantage to the method.

What about cost? In an accompanying paper the authors try to estimate the difference:

The time horizon was 12 months and costs were estimated from the UK National Health Service perspective. Cost effectiveness outcomes are expressed in terms of incremental costs per ulcer-free day (cost effectiveness analysis) and incremental costs per quality adjusted life years (cost utility analysis).

Results The larvae arms were pooled for the main analysis. Treatment with larval therapy cost, on average, £96.70 (109.61; $140.57) more per participant per year (95% confidence interval -£491.9 to £685.8) than treatment with hydrogel. Participants treated with larval therapy healed, on average, 2.42 days before those in the hydrogel arm (95% confidence interval -0.95 to 31.91 days) and had a slightly better health related quality of life, as the annual difference in QALYs was 0.011 (95% confidence interval -0.067 to 0.071). However, none of these differences was statistically significant. The incremental cost effectiveness ratio for the base case analysis was estimated at £8826 per QALY gained and £40 per ulcer-free day. Considerable uncertainty surrounds the outcome estimates.

One of the things you can see -- and the authors are straightforward about it -- is that the estimates they make for cost and outcome aren't especially precise despite the fairly large patient population. This is probably a reflection of the wide variability in the condition itself. All ulcers are not the same. So on the basis of these data you might or might not want to make a policy decision about what you will pay for. What this tells you about this particular kind of ancient form of therapy probably depends upon your predisposition about "complementary medicine." The evidence here doesn't establish a clear superiority for larval therapy, although it certainly shows it at least the equal of conventional therapy. But it costs more and the patient may not be as comfortable during the course of therapy.

Trade-offs. As much as we try to be precise and quantitative in medicine, it is like everything else in life -- a balancing act.


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I always thought that "Is your cup half full or half empty" challenge to be a particularly vacuous one. If someone asks me that question, I tell them it depends entirely upon whether I'm filling the cup (in which case it's half full) or drinking from it, (in which case it's half-empty).

50% of a cup is 50% of a cup and trying to divine someone's outlook from such a deepak question is as bogus as alternative medicine. It's what I call "Janeway psychiatry" after the Star Trek: Voyager TV show, where the captain is always right, always incisive and all mental conditions can be resolved optimally in 40 minutes!

Ian: Feel free to translate to: it depends how you look at it. Which is, after all, what it means (when not taken literally).

My mother-in-law gets these ulcers and they are at times very painful. The higher level of pain in the maggot groups seems like a BIG disadvantage to me.

By Marilyn Mann (not verified) on 21 Mar 2009 #permalink

The interesting thing about CAM is that statistically, its more utilized by those who have college degrees and the propensity of those taking advantage of CAM pay out of pocket (due to CAM often not being covered by insurance). Clearly, as the more conservative and prevention/wellness driven physician in my community, I'm VERY busy. The perception and the reality (my opinion)of CAM is how the risk/benefit see-saw provides for minimized risk and often times, similar, if not better sustainable benefits.

In my earlier years as a family physician (mid-70's), under my care was a patient with dry gangrene of some toes. She was located in an un-air-conditioned wing of one of the hospitals in a relatively small city in the Northeast. On one of my daily rounds on that patient, I was aghast at the appearance of fly larvae feeding on the gangrenous toes and the invovled interdigital spaces. The unaffected toes on that foot had not one larva; they were clearly only interested in the necrotic tissue.

The response of the older, more experience orthopodedic consultant, when he answered my stat phone call was, "Great! Let 'em be." And I was educated about this age-old therapy.

If I remember correctly (memory not so great anymore) the treatment for dry gangrene was to allow it to spontaneously demarcate the eventual line between final necrotic tissue (to be amputated) and viable tissue, since that approach limited the extent of ultimate amputation as opposed to pre-emptive amputation (I don't remember if this was true for all cases, but there was no threat of systemic involvement in this expectantly treated case of dry gangrene). There was also no MRSA around then.

Ultimately, the situation worked out fine. Our little assistants greatly shortened the observation period (and thus the length of hospital stay), the patient experienced absolutely no pain at all, since as opposed to decubitus ulcers, there was no underlying viable tissue involved (and the critters were very discriminating in there preference for only dead, no longer innervated tissue), and they joined the health care team SPONTEOUSLY, their arrival facilitated by some passing fly in the open-windowed wing.

So, though quite anecdotal, no added expense for this added therapeutic measure, no pain, and a "significant difference" in shortened hospital stay. A case of "Natural Healing" (alternative medicine) combined with scientifically based allopathic medicine to achieve an improved outcome.


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revere dear, your BMJ link doesn't connect to the paper. I tried it yesterday too.
I have a question and that's why I was trying to get to the paper. It's most likely a dumbass question, simply because I'm not a medical person however, how much ulcer pain did the patients experience after the maggot treatment?
Significant ? Tolerable ?

Lea: I think I've fixed the link. In any event, pain was measured subjectively via a "score" obtained by having the subject point along a line (that I think was 15 cm long) with one end intolerable pain and the other nothing. The outcome compared the average of these somewhat arbitrary scores. I hope you'll be able to see the details now with the link fixed.

Thank you revere. And thanks for explaining the pain score thingy.
Pain is an important indicator to me as I do understand it's implications, in degree that is. One of the understandings I have is the brain is primarily responsible for what the rest of the body is feeling.

Marilyn Mann: Should you see this; leg ulcers are what killed my step-father. Course he was a lazy and useless individual.