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Despite modern wound treatment and broad-spectrum antibiotic treatment, patients with chronic wounds still exist. The appearance of antibiotic resistant bacteria, such as methicillin-resistant Staphylococcus aureus (MRSA) in the 1980s and ’90s, gave rise to a search for other remedies. One of the remedies that has been rediscovered and subsequently successfully reintroduced is maggot debridement therapy (MDT).1 The fact that more than 100 articles were published on the subject in the past two decades indicates that the use of maggots is making a strong comeback in medicine.2 In January 2004, the U.S. Food and Drug Administration (FDA) issued 510(k)#33391, allowing production and marketing of maggots as a medical device. In this article, we discuss the use of MDT in patients with a chronic wound.

A Long History of Maggot Therapy

MDT has been used in many cultures and has been known for centuries.3 Ambroise Parè is credited as the father of modern MDT. Unfortunately, no evidence can be found of Parè using maggots as a means to clean or heal wounds. The only reference is the often-cited case that occurred in 1557 at the battle of St. Quentin, when Parè observed soldiers whose wounds were covered by maggots. He mainly described the negative effects of the maggots, and, above all, believed they were spontaneously produced by the wound itself, not by the eggs of fly.4

Baron Larey (1766-1842) a famous surgeon in the army of Napoleon Bonaparte, wrote about soldiers who had larvae-infested wounds, but was frustrated that it was difficult to persuade his patients to leave the maggots in place, believing that “they promoted healing without leaving any damage.”5

The first surgeon to use MDT in patients in the hospital was the orthopedic surgeon William Baer. In the 1920s he was faced with a group of untreatable patients with severe osteomyelitis (antibiotics had not yet been discovered). He successfully treated many patients with maggots, and because of his success the therapy became regularly used in the United States.6

By 1934 more than 1,000 surgeons were using maggot therapy. Surgical Maggots were available commercially from Lederle Corporation.7 But with the introduction of antibiotics in the 1940s, the use of maggots dropped off. In the following years, case reports were published only occasionally.

Figure 1: This patient had a malignant tumor of the leg removed and underwent post-operative radiotherapy. The wound contains necrosis and slough. An earlier sharp debridement and split skin graft produced no effect.

Figure 1: This patient had a malignant tumor of the leg removed and underwent post-operative radiotherapy. The wound contains necrosis and slough. An earlier sharp debridement and split skin graft produced no effect.

The Negative Image of Maggots

A large problem of MDT is the difficulty of this type of therapy to gain acceptance in the medical community. Maggots are associated with rotting and decay. The image is of filthy, low-life creatures that are ugly and disgusting. Although a nice recent example for the general public is the scene in the movie Gladiator. The main character (played by Russell Crow) is advised to leave the maggots that spontaneously infested a wound on his shoulder in place so that the wound would heal. He leaves them in place and the wound heals without any problem, enabling Crow’s character to fight many battles.

In contrast, in an oral presentation we held recently at a Dutch scientific surgical meeting, a surgical professor in the audience said, “I will never allow those creatures in my ward.”8 This remark shows that widespread use and acceptance of MDT has not yet been reached. It seems there is still much work to do before MDT is generally accepted as a therapeutic method.

Fortunately, the negative image that seems to exist among nurses and physicians does not seem to bother patients.9 We have treated more than 100 patients in our clinic with MDT. All patients to whom we proposed MDT agreed to the therapy. All were allowed to discontinue the therapy whenever they wanted; none did. In a survey of the first 38 MDT-treated patients, 89% agreed to another session of MDT if the surgeon believed it would be beneficial, and 94% of the patients said that they would recommend it to others. This is despite the fact that the therapy was not successful in all patients (there was a below-knee of above the knee amputation-rate of 19% among patients who underwent MDT).10

Figure 2: The full-grown maggots are removed after three days of treatment. There is no necrosis left. The wound was treated with four applications with a total of 145 maggots. The wound was subsequently treated with vacuum-assisted closure therapy and secondarily closed.

Figure 2: The full-grown maggots are removed after three days of treatment. There is no necrosis left. The wound was treated with four applications with a total of 145 maggots. The wound was subsequently treated with vacuum-assisted closure therapy and secondarily closed.

Indications and Evidence

Indications and contra-indications for maggot therapy are not well defined. Some state that all kind of wounds that contain necrosis or slough can be good candidates for MDT. In our own study of 101 patients with 116 wounds treated with maggots, we had an overall success rate of 67%. (Seventy-eight out of 116 wounds had a beneficial outcome.) However, in 13 patients with septic arthritis, all wounds failed. Success rates where significantly reduced in cases of chronic limb ischemia, visible tendon or bone, and in cases of duration longer than three months before the start of MDT.11

Most physicians who start MDT use it mainly for worst-case scenarios. From our previous studies, it is clear that success rates in those patients are low. After witnessing a few failures, the physician is naturally reluctant to use it again.

What about evidence? Large randomized studies are lacking, although one containing 600 venous ulcer patients was initiated in 2004.12 There have been three randomized studies performed. Wayman, et al., have shown the cost-effectiveness of larval therapy in venous ulcers compared with hydrogel dressing.13 Contreras, et al., could not find a difference between MDT and curettage and topical silver sulfadiazine in patients with venous leg ulcers.14 At the 36th annual meeting of the European Association for the Study of Diabetes, Markevich, et al., reported on a randomized, multicenter, double-blind controlled clinical trial (n=140) for neuropathic diabetic foot lesions compared to conventional treatment. They found a significant higher percentage of granulation tissue after 10 days, compared with the hydrogel group.15 Results from large case-series indicate that MDT works and could even save limbs.2,16-18 The mechanism of action has not been unraveled yet.

Figure 3: A patient with a necrotizing fasciitis of the left upper leg is treated with the contained technique. There is no normal proximal skin border, which would be needed for the free-range technique.

Figure 3: A patient with a necrotizing fasciitis of the left upper leg is treated with the contained technique. There is no normal proximal skin border, which would be needed for the free-range technique.

Factors Influencing Effectiveness of MDT

Unfortunately, the statement made by Thomas, who said that maggot therapy works by “secreting proteolytic enzymes that break down dead tissue, turning it into a soup, which they then ingest,” still holds.19 It is known that there are mechanical effects, tissue growth effects, that direct killing of bacteria in the alimentary tract of the maggot takes place, and that maggots produce antibacterial factors.2,17,20-31

Although maggots are suitable agents for chronic wound treatment, it is likely that some wounds are more eligible than others for this type of treatment. In our opinion, all wounds that contain gangrenous or necrotic tissue with infection seem to be suited for MDT.32 Success rates of MDT reported in literature vary, but seem to be around 80% to 90%.16,17,33 In our own series, success rate is about 70%.

Patient-selection (case-mix) and method of outcome measurement play essential roles in these percentages. In our opinion, all wounds that contain necrotic tissue can be debrided effectively with MDT. However, if for example wound ischemia is the major etiologic factor, this should also be addressed. In our experience, diabetic foot, venous ulcers, traumatic ulcers, and infections after surgical procedures are all good candidates for MDT.

Although maggots are suitable agents for chronic wound treatment, it is likely that some wounds are more eligible than others for this type of treatment.

Absolute contraindications in our opinion are wounds close to large, uncovered blood vessels and wounds that need immediate surgical debridement (e.g., in the case of a septic patient). A relative contraindication is patients with natural of medically induced coagulopathies, but also patient preference could play a role.34 We have had very bad results with infected small joints of the foot; all wounds (n=13) eventually needed a small or large amputation.

Even the technique of application has an effect on outcome. There are two different application techniques: the free-range and the contained technique. The free-range technique is more effective in vitro and in-vivo and has become our standard application technique—not only in the outpatient department, but also in the intra-mural setting.35,36 (Figure 1, p. 16, shows a patient with a necrotic wound on the leg after radiation therapy and a surgical excision for a malignant tumor was performed.) Earlier surgical debridement combined with split skin graft failed. After four applications of maggots, the wound was free of necrosis and could be subsequently closed. (See Figure 2, p. 16.)

The contained technique is used in patients with bleeding tendencies and wounds that do not have enough healthy skin surrounding the wound; in other words, where the covering “cage” needed in case of the free-range technique can’t be applied. (This problem is shown in Figure 3, p. 16: A patient with necrotizing fasciitis of the left upper leg was treated with the contained technique—BiologiQ, Apeldoorn, Netherlands—as there is no proximal skin border. Of course, patient preference plays a role as well in the choice of application technique.37

In our clinic, we have treated more than a hundred patients with MDT, and all patients to whom we proposed MDT to agreed to the therapy.

Wound Clinic

In the Netherlands maggots can be ordered easily and are delivered within 24 hours. We started a wound clinic in 2002. First it was for MDT alone, but now the scope is broader, and we treat chronic wounds with different kind of wound therapies. We have two nurses, one nurse practitioner, one resident-surgeon, and one vascular surgeon who apply the maggots.

Patients do not need to be admitted for MDT. Fifty-nine percent of our patients are treated in the outpatient department. We are able to treat as many as 10 or 15 patients in one session, but MDT-treated patients make up only two or three patients at a time.

We found that after fast, successful biological debridement with MDT we were left with a lot of patients with red, granulating wounds that needed our attention in order to prevent relapses. In our opinion, there are many different treatment methods after MDT. Plaster casting in case of diabetic feet, secondary closure, and split skin grafting are different methods. However, other therapies like VAC-therapy and recently OASIS are promising.

At this time, all patients are prospectively followed after MDT. We are especially interested in patient selection and are now also aiming to find the ideal wound therapy after MDT. TH

Dr. Steenvoorde is a resident surgeon at Rijnland Hospital Leiderdorp, the Netherlands. van Doorn is a nurse-practitioner at Rijnland Hospital Leiderdorp. Jacobi is a senior researcher in the Medical Decision Department at Leiden University Medical Center, in the Netherlands. Dr. Oskam is a vascular surgeon at Rijnland Hospital Leiderdorp.

References

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