MAGGOT THERAPY - THE LAST FIVE YEARS
Ronald A. Sherman, MD, Msc, Assistant Professor of Medicine
Depts. of Medicine and Pathology, University of California, Irvine, CA, USA

Perhaps there is no greater evidence of the continued need for better wound care therapeutics than the fact that live blow-fly larvae (maggots) have found their way back into medical practice for that purpose. In combination with surgery, maggot therapy was used during the early decades of this century for treating osteomyelitis and purulent soft tissue infections. Since the 1940s, when antibiotics became widely available, maggot therapy was used only as a last resort. During the past ten years, however, maggot therapy has been used increasingly and successfully in the treatment of various chronic soft tissue wounds, including neurovascular ulcers, venous stasis wounds, pressure ulcers, traumatic and surgical wounds, burns, and necrotic tumors.

The year 1995 remains a landmark in the history of maggot therapy, also known as larval therapy¹, maggot debridement therapy (MDT)², or biodebridement.^3,4 It was the year that maggot therapy was first discussed by the ETRS Working Party on Debridement, as later published in this journal.⁵ 1995 also saw the publication of the first controlled prospective trial of maggot therapy,⁶ demonstrating a significant improvement in the rate of healing associated with maggot therapy for treating pressure ulcers in spinal cord injured patients. Maggot therapy was also featured on the front pages of The Wall Street Journal and The Times, in London; and television audiences throughout Europe and North America watched medicinal maggots at work. How has the field of maggot therapy developed since 1995, and what predictions can be made about its future?

The clinical use of medicinal maggots has increased steadily over the past five years. Worldwide, the number of practitioners or centres employing this therapy has increased from less than a dozen, in 1995, to almost 1,000 today. Our laboratory is one of two that produce medicinal maggots for use in the United States. Combined, the two laboratories now supply over 300 treatments per year to more than 70 US practitioners. Use of larval therapy is ten times greater in the United Kingdom, where 10,000 treatments were sent out by the Surgical Materials Testing Laboratory (Bridgend, Wales) to 700 centres over the past five years.

In Israel, over 1,000 treatments have now been administered in hospitals, clinics and nursing homes to over 100 patients with 178 wounds (median number of treatments per wound: 4). Debridement and healing has been noted in diabetic foot ulcers, venous stasis ulcers, and other chronic wounds which had previously failed two or more conventional treatments.^7,8

In Western Europe, distribution of medicinal maggots is currently hindered by governmental concerns over the most appropriate way to oversee and regulate their production and use. Nevertheless, centres in Austria, Germany,^9,10 Hungary,¹¹ Sweden,¹² Switzerland¹³ and elsewhere all have gained considerable experience with maggot debridement during the past few years. Some centres already have treated hundreds of patients.

The International Biotherapy Society was formed in 1996 (http://www.homestead.com/biotherapy/). This professional organization is dedicated to supporting research and clinical use of maggot therapy and other biological therapeutics (apitherapy, leech therapy, debriding fish, etc). The Fifth Inter-national Conference on Biotherapy took place this year in Wurzburg, Germany, where some of the current research efforts were presented.

Maggot therapy is recognized to work by three main actions: debridement, or liquefaction of necrotic tissue; disinfection; and hastened wound healing. The mechanisms underlying all three aspects are being investigated by several laboratories around the world. Mumcuoglu and colleagues provided new evidence for the elaboration of growth-promoting cytokines, as a mechanism by which medicinal maggots promote granulation tissue.¹⁴ More experimental evidence was presented to demonstrate the antimicrobial action of maggot ingestion.¹⁵ The potential complications of using non-sterile maggots, or maggots of different species, also was discussed.13 Simplifying the application of maggot dressings continues to receive attention, and Fleischmann and Thoener¹⁶ presented a novel design whereby the maggots are completely contained in their own cage, separated from, but in contact with, the patient.

From the progress over the past five years, it is reasonable to make some predictions about the short term future of maggot therapy. As practitioners become more comfortable with maggot therapy, as more non-physicians participate in its performance, and as maggot therapy becomes the treatment of choice for specific wounds in otherwise healthy patients, rather than the treatment of last resort in the very ill, then out-patient maggot therapy will become much more common than in-patient therapy.

The majority of maggot therapy literature is anecdotal. A large-scale prospective study is still lacking. Such a study - preferably a multi-centre trial - likely will be established very soon. A cost analysis must be included in the study. Unfortunately, there is little commercial incentive to fund such a trial, so finding support may be problematic. Perhaps the laboratories which sell medicinal maggots will at least donate larvae, since they have a financial interest in the widespread acceptance of this treatment.

Assuming that it is as effective and safe as the data so far suggests, maggot therapy fits the needs of any community where chronic wounds are endemic, and where antibiotics or surgery are either ineffective, associated with high risk, or unavailable. Clearly, this picture fits not only the developed countries within Europe, North America and Israel, but also developing nations. Therefore, it is hoped that maggot debridement will soon be tailored to the needs of tropical and developing countries, so that they, too, can reap its potential benefits.

The veterinary applications of maggot debridement are still unknown. The first study of maggot therapy in work animals is now underway in Egypt, and preliminary information may soon be forthcoming.

The International Biotherapy Society, in concert with members of the ETRS, should now work towards establishing guidelines for the use, preparation and handling of medicinal maggots. By establishing such standards, it may be possible to overcome the regulatory impasse in Europe, currently limiting the availability of medicinal maggots. With the participation and support of an international panel of experts, such professional standards may achieve worldwide acceptance more quickly and easily than otherwise would be possible.

Maggot therapy continues to suffer a serious public relations problem. Maggots are viewed as the antithesis of health and cleanliness. The fact that they are being invited back into 21st-century hospitals suggests that they have much to offer. Continued public discussion of maggot therapy, and incorporation of therapeutic myiasis into our art and literature (Prince Valiant, by John Cullen Murphy and King Features Syndicate; Chicago Hope, by 20th Century Fox Television; Gladiators, by Dreamworks Motion Picture Studios) will help debride the cultural and emotional barriers that can obstruct the rational evaluation of data. Half a century ago, the maggot was forsaken for the promise of antibiotics. Hopefully, this time around we will not let our fears or cultural biases or new technologies prevent us from learning everything we can about the medicinal maggot, and subsequently harnessing its power for the benefit of wound-healing.