When Should Contained Maggot Therapy Be Used for Wound Debridement?
by Ronald Sherman MD, MSC, DTM&H
In a previous post, we learned that all clinical studies to date and all but one laboratory study indicate that contained ("bagged") maggots are effective in wound debridement, but less so than "free-range" (or "non-bagged") larvae. Why, then, are they used? What are the attributes of contained maggots that make them worth sacrificing the efficacy and efficiency of conventional "free-range" maggots?
The primary objectives of applying medicinal maggots within containment bags have been:
- To simplify the process of applying the maggots and avoid handling the maggots individually;
- To decrease pain by preventing the maggots from having direct contact with the wound bed, and by preventing them from crawling into the sinus tracts and undermined areas of the wound; and
- To prevent the maggots from escaping prematurely from the dressings before they can be removed by the therapist.
How well have bagged maggots achieved these intended benefits?
Contained Maggot Therapy Application
Regarding ease of application, contained maggots (i.e., Biobag™ by Biomonde, UK) allows the therapist to apply one or multiple bags of maggots to the wound, instead of having to handle individual larvae. This is significantly simpler than the older, but still common method of pouring individual maggots out of a bottle (and maybe even counting them) onto the wound or wound dressing (i.e., LarvE™ by Biomonde, UK; and many other brands). One would expect the contained maggots to be the faster method of application, but in the only published comparison, Steenvoorde and colleagues reported no significant difference in dressing application time between methods.1 Another method of simplifying the application of maggot therapy was developed over 20 years at the University of California: maggot-impregnated gauze. With this product (now sold by Monarch Labs, Irvine, CA, under the brand name Medical Maggots™) the larvae are applied to the wound bed not within a bag, but as one or two pieces of maggot-impregnated gauze, which is then covered by a confinement dressing. It could reasonably be assumed that this method should be simpler and faster than applying individual maggots, but not as quick and simple as applying maggots within a containment bag; but a head-to-head comparison with either of those methods has not yet been published.
Have containment bags kept their promise of reducing pain or preventing maggot escapes? Dumville et al2 found no difference in frequency of pain between their bagged and free-range maggot therapy groups. In 2005, Steenvoorde and colleagues3 reported no difference between contained and confined maggot dressings in terms of the frequency of escapes. In short, researchers have not documented that contained maggot dressings are associated with any significant reduction in the occurrence of pain, nor a reduction in the frequency of escapes, nor a reduction in time and effort of dressing application, compared to confined ("free-range") maggots.
Another important consideration when choosing between bagged maggots and free-range maggots is the cost difference. Bagged maggots are much more costly because the procedure to make them is more labor-intensive. The cost of therapy with bagged maggots is also more expensive because it takes two or more times as many larvae and two or more times as many applications, on average, to effect the same outcome (debridement), compared to free-range maggots.2,3,4 In other words, the treatment cost, per wound, of using contained maggots can be four or more times as great as that of using free-range maggots.
Wounds That Call for Contained Maggots
So, with questionable benefits and increased cost, with comparatively less efficacy and efficiency based on the studies-to-date, why would a therapist use contained maggots? One reason is simply the stigma or "yuk-factor" associated with maggots. Many people prefer the idea of maggots in a bag rather than maggots freely crawling along the wound bed in search of necrosis and infection. For another, sometimes we want the maggots not to access all of the wound areas, especially if there is a friable blood vessel or other structure in the wound that the maggots should avoid. Bagged maggots are also valuable when we have little or no structures around the wound on which to apply the confinement dressing. These are the situations when I usually turn to containment bags.
The two times I have used or recommended bagged maggots have been when I was treating a periorbital wound and when I was asked to recommend a maggot dressing to debride oropharyngeal mucormycosis. In the first case, I was willing to sacrifice efficacy and speed for the sake of containing the maggots where there was not enough peripheral skin to mount a conventional maggot confinement dressing...the border of the wound was the margin of the eye. The treatment worked well, though several applications were needed (the median number of applications needed to debride a wound with free-range maggots is just one two-day cycle).
In the second case, I was asked to recommend maggot debridement dressings for an immunosuppressed girl in the intensive care unit, dying from an aggressive leukemia, whose soft palate was now being destroyed by an invasive fungal infection: mucormycosis (also known as zygomycosis). Surgical resection was considered to be too risky. Again, containment bags allowed the maggot dressing to be placed where there was no surface to support a conventional confinement dressing. Ultimately, maggot therapy was not provided because, at this point, the girl's family decided to halt all further interventions. She passed away two days later.
So, when should maggot therapy be administered in containment dressings instead of standard confinement dressings? Most authorities would suggest their use for wounds in or near an orifice, where confinement dressings cannot easily be mounted, or when patients (or more likely their clinicians) are too uncomfortable to use free-range confinement dressings. During the decision-making process, patients and therapists also should remember that the financial costs and total debridement times could be 2 to 4 times longer. Although I have had only two occasions in the past that warranted their use, I am glad that maggot containment dressings are finally available commercially so that I no longer have to roll my own. Based on the current data, contained maggots may deliver less bang for the buck, but sometimes they are just what the doctor needs to order.
1. Steenvoorde P, Oskam J. Comments on the paper, "The biosurgical wound debridement: experimental investigation of efficiency and practicability," by Blake FA et al. Wound Repair Regen. 2008 May-Jun;16(3):466.
2. Dumville JC, Worthy G, Bland JM, Cullum N, Dowson C, Iglesias C, Mitchell JL, Nelson EA, Soares MO, Torgerson DJ; VenUS II team. Larval therapy for leg ulcers (VenUS II): randomised controlled trial. BMJ. 2009;338:b773.
3. Steenvoorde P, Buddingh TJ, van Engeland A, Oskam J. Maggot therapy and the "yuk" factor: an issue for the patient? Wound Repair Regen. 2005;13:350-2.
4. Thomas S, Wynn K, Fowler T, Jones M. The effect of containment on the properties of sterile maggots. Br J Nurs. 2002; 11(12 Suppl):S21-2, S24, S26 passim.
Disclosure: Financial - The author is Co-founder and Laboratory Director of Monarch Labs.
About The Author
Ronald Sherman MD, MSC, DTM&H has led a long career at the forefront of biotherapy, pioneering the development of medicinal maggots for over 25 years. He is now retired from his faculty position at the University of California, but continues to volunteer as Director and Board Chair of the BTER Foundation, and as Laboratory Director of Monarch Labs.
The views and opinions expressed in this blog are solely those of the author, and do not represent the views of WoundSource, Kestrel Health Information, Inc., its affiliates, or subsidiary companies.