Q: What is maggot debridement therapy?
A: Medicinal larvae (larvae of the green blowfly Phaenicia sericata, also known as Lucilia sericata) can be placed in a properly prepared chronic wound to facilitate debridement (Figure 1). This is commonly referred to as maggot debridement therapy (MDT).
Historically, maggots were used for medicinal purposes by ancient cultures such as the Mayan Indians of Central America and the Ngemba tribe of New South Wales, Australia. 1 However, MDT was not commonly used in the western hemisphere until the mid-nineteenth century. 2 In the United States, J.F. Zacharias used MDT during the Civil War, drawing on the experience of European military surgeons.
One of the first documented intentional uses of maggots for skin infections in the United States occurred in the early 1930s. 3,4 During World War I, an orthopedic surgeon named William Baer became interested in MDT. He transferred his knowledge from the battlefield and applied it to his pediatric patients with osteomyelitis; their chronic wounds healed within 6 weeks of starting MDT. In 1929, Dr Baer presented the results of these and other successes at Johns Hopkins and Baltimore Children’s Hospital, 3 and his outcomes were published in 1931. 4 By the mid-1940s, MDT was extensively utilized and researched until it fell out of favor due to its high cost.
MDT was reintroduced in the mid-1980s by Bunkis et al when they reported improvement in chronic wounds that exhibited incidental myiasis. 5 More recently, MDT has gained popularity for use in individuals with lower extremity wounds that are unresponsive to proactive care. 6–9
Use of MDT has steadily increased during the past 10 years, particularly in many progressive, high-volume wound care centers in Europe and Asia; it has been less commonly used in the United States. 10,11 Drs Ronald Sherman from the United States and Steve Thomas from the United Kingdom are considered by many to be the fathers of modern MDT. 12
Q: Why is MDT thought to be effective in managing chronic wounds?
A: The larvae feed on the necrotic tissue and exudate, which may assist in removing bacteria from the wound. In addition, maggot saliva and digestive secretions appear to have proteolytic and antibacterial properties. 13–15 The movement of the maggots may also help stimulate formation of granulation tissue. 6,13
MDT has been shown to be effective in aiding the treatment of intractable diabetic foot ulcerations, which frequently result in hospitalization; amputation is required in 15% to 25% of these cases in the industrialized world. 16 MDT is also effective in preparing wound beds for treatment with other wound healing modalities, such as growth factor therapies, bioengineered tissue, and hyaluronan-based dressings. 17,18
Q: How is MDT applied to a wound?
A: Prior to application of MDT, manual sharp debridement of the ulcer should be performed to remove as much eschar as possible; larvae do not penetrate eschar as easily as they do other necrotic tissues. The larvae may burrow under the eschar, facilitating easier removal at the next dressing change.
Next, a skin adhesive should be applied to the periwound skin. The adhesive will facilitate the application of a periwound barrier made of a thin hydrocolloid dressing or waterproof tape. The dressing should be cut into strips and applied to the circumference of the wound. The dressing will aid in reducing the migration of larvae outside the intended debridement area.
After these steps are completed, the wound is ready for the application of medicinal larvae. The larvae are disinfected by a process that includes washing the eggs in a solution of sodium hypochlorite 0.05%. The larvae are then applied directly to a nylon chiffon dressing (Figure 2) and transferred to the wound. Water-resistant foam tape should be used to secure the ends of the nylon chiffon dressing. The average number of larvae generally required for adequate wound debridement is 10 maggots per square centimeter of wound.
Moist gauze should be applied to the dressing to provide moisture to the larvae, followed by a secondary air-permeable dressing with a protective gauze layer to absorb drainage from the wound. If the wound is located in an area of pressure, strict off-loading of weight must be accomplished to avoid disturbing the larvae and increasing the chance of migration beyond the wound.
The patient should return to the office or clinic in 2 to 3 days for a dressing change. However, the patient may need to change the outer air-permeable dressing prior to the dressing change, depending on the amount of drainage (which is typically a yellowgreen color). The outside dressing is changed only if there is a significant amount of drainage. The amount of drainage will vary by the type of ulceration.
Q: For what types of wounds is MDT indicated?
A: MDT may be used for all types of wounds with necrotic or fibrous tissue that requires debridement, regardless of the ulcer’s underlying etiology—which means it is indicated for ulcers due to arterial disease, venous stasis, pressure, or diabetes, whether infected or not. MDT may be helpful in the treatment of infected ulcers by decreasing the bacterial load and possibly decreasing the risk of amputation and sepsis. MDT has been shown to be effective against many strains of bacteria, including methicillin-resistant Staphylococcus aureus.15
Different types of wounds are treated with MDT in the same manner, with the exception of wounds with increased drainage. Those wounds may require more frequent changes of the air-permeable dressing.
Finally, MDT may be used in ambulatory or hospitalized patients.
Q: When is MDT contraindicated?
A: Possible contraindications for the use of MDT include life- or limb-threatening infections, lack of wound hemostasis, adhesive allergies, deep tracking wounds, psychological issues, pain, and hypersensitivity to maggot movement. Patients may become less tolerant of the therapy as the wound approaches 100% debridement and the larva begin to encroach on viable tissue. Osteomyelitis and arterial insufficiency have been listed as relative contraindications 19; however, the authors’ experience in treating these types of wounds with MDT has been encouraging, as long as the underlying condition is not ignored.
Current use of MDT has suggested that it is an acceptable and readily performed technique. Patients are intrigued by this modality when it is presented to them as an alternative in treating a chronic wound. Education about successful outcomes using MDT and the larval life cycle can alleviate fears and help convince patients and family members who are reluctant to participate.
Results of studies and anecdotal evidence suggest that appropriate use of MDT may effectively treat diabetic foot wounds, as well as other chronic wounds. Benefits of MDT in the diabetic population may include preventing progression of diabetic foot ulceration, improving health-related quality of life, and saving significant overall cost. This treatment modality may also show promise as an alternative to operative debridement in patients with diabetes at high risk for lower-extremity amputation. Continued interest in MDT may lead to continued investigation and widespread usage, elucidating its utility in the treatment of diabetic foot wounds. Ultimately, this may yield improved results in therapy and, perhaps, a reduction in the high prevalence of unnecessary lower-extremity amputations in developed and underdeveloped countries worldwide.
1. Rayman A, Stansfield G, Woolard T, Mackie A, Rayman G. Use of larvae in the treatment of the diabetic necrotic foot. Diabetic Foot 1998; 1:7–13.
2. Root-Bernstein R. Honey, Mud, Maggots and Other Medical Marvels: The Science Behind Folk Remedies and Old Wives’ Tales. Boston, MA: Houghton Mifflin Company; 1997.
3. Baer WS. Sacroiliac joint—arthritis deformans—viable antiseptic in chronic osteomyelitis. Proc Int Assembly Interstate Postgrad Med Assoc North Am 1929; 371:365–72.
4. Baer WS. The treatment of chronic osteomyelitis with the maggot. J Bone Joint Surg 1931; 13:438–75.
5. Bunkis J, Gherini S, Walton RL. Maggot therapy revisited. West J Med 1985; 142:554–56.
6. Mumcuoglu KY, Ingber A, Gilead L, Stessman J, et al. Maggot therapy for the treatment of diabetic foot ulcers. Diabetes Care 1998; 21:2030–1.
7. Mumcuoglu KY, Ingber A, Gilead L, et al. Maggot therapy for the treatment of intractable wounds. Int J Dermatol 1999; 38:623–7.
8. Mumcuoglu KY. Clinical applications for maggots in wound care. Am J Clin Dermatol 2001; 2( 4):219–27.
9. Sherman RA, Sherman J, Gilead L, Lipo M, Mumcuoglu KY. Maggot debridement therapy in outpatients. Arch Phys Med Rehabil 2001; 82:1226–9.
10. Shinkman R. Worms and squirms. Maggots, leeches are making a comeback in modern medicine. Mod Healthc 2000; 30:54–5.
11. Thomas S, Jones M, Wynn K, Fowler T. The current status of maggot therapy in wound healing. Br J Nurs 2001; 10( 22):S5–S8, S10, S12.
12. Bonn D. Maggot therapy: an alternative for wound infection. Lancet 2000; 356:1174.
13. Vistnes LM, Lee R, Ksander GA. Proteolytic activity of blowfly larvae secretions in experimental burns. Surgery 1981; 90:835–41.
14. Mumcuoglu KY, Miller J, Mumcuoglu M, Friger M, Tarshis M. Destruction of bacteria in the digestive tract of the maggot of Lucilia sericata
(Diptera: Calliphoridae). J Med Entomol 2001; 38:161–6.
15. Wolff H, Hansson C. Larval therapy for a leg ulcer with methicillin-resistant Staphylococcus aureus. Acta Derm Venereol 1999; 79:320–1.
16. Frykberg RG. Epidemiology of the diabetic foot: ulcerations and amputations. Adv Wound Care 1999; 12:139–41.
17. Armstrong DG, Mossel J, Short B, Nixon BP, Knowles EA, Boulton AJ. Maggot debridement therapy: a primer. J Am Podiatr Med Assoc 2002; 92:398–401.
18. Knowles A, Findlow A, Jackson N. Management of a diabetic foot ulcer using larval therapy. Nurs Stand 2001; 16( 6):73–6.
19. Sherman RA. Maggot therapy for foot and leg wounds. Lower Extremity Wounds 2002; 1( 2):135–42.
EVIDENCE FOR USING MAGGOT DEBRIDEMENT THERAPY
In addition to volumes of anecdotal experience available in print regarding maggot debridement therapy (MDT), a handful of prospective trials have been reported.
- In 1995, Sherman et al 1 studied a group of 20 patients with pressure ulcers who were treated with MDT. In 8 of 20 patients, wounds were followed for 3 to 4 weeks prior to initiation of MDT. Pressure ulcers were graded as Stage III or IV and ranged in size from 5 cm2 to 30 cm2; the ulcers were located on either pelvic or pedal areas. When comparing MDT with conventional therapy, the authors found a 21.8% increase in wound surface area prior to initiation and a 22% decrease in wound surface area per week after initiation of MDT. The time to achieve debridement was approximately 10 days using MDT versus more than 28 days in the control group. Prior to this study, only one case report had been elucidated on MDT use in pressure ulcers.
- In 1998, successful accounts of MDT treatment in nonhealing diabetic foot ulcers were reported by Mumcuoglu et al. 2 In their study, 27 nonhealing wounds in 22 patients were documented. Twenty-four MDT-treated wounds were completely or significantly debrided within an average of 2 weeks, with 12 wounds debrided in 1 week.
- In 1999, Fleischmann et al 3 reported that they found MDT to be valuable in treating diabetic foot wounds.
- In 2000, Sherman et al 4 evaluated effects of MDT on multiple wound types in 43 patients who were followed pre- and post-MDT. For the conventional treatment group, wounds increased in size on average by 4 cm2, from 19 cm2 to 23 cm2 over 2 months (a difference of 4.2%). Patients treated with MDT demonstrated decreased wound surface areas, from 24 cm2 to 17.6 cm2 (a difference of –6.3%). A statistically significant difference in the degree of debridement (surface area of necrotic tissue) per day between the 2 study arms was also detected. The average surface area of necrotic tissue in the conventional arm increased from 6.8 cm2 to 9.0 cm2 over 33 days; in the MDT-treated group, it decreased from 6.2 cm2 to 0.7 cm2 in 18 days.
- In 2002, Sherman 5 examined a cohort of 103 patients with 145 pressure ulcers. Patients from this group were selected after evaluating the quantifiable debridement for the first 2 ulcers per patient if and when photographs and tracings were present and reliable. Patients with complex wounds or less than 2 weeks of follow-up were excluded. This limited the number of patients to 67 and number of wounds to 92. Ulcer dimensions were digitally recorded. Forty-nine wounds were treated conventionally and 43 wounds received MDT. Eighty percent of MDT-treated wounds were completely debrided in less than 5 weeks compared with 52% of conventional wounds (P = .021). Eighty-four percent of MDT-treated wounds decreased in size during therapy, compared with 37% in the conventional group (P <.001). Analysis of variance (ANOVA) was used to assess debridement efficacy and showed that MDT-treated wounds exhibited an average decrease of 3.7 cm2 within the first 2 weeks of treatment.
In addition, 31 MDT-treated wounds were initially monitored during conventional treatment; the total wound size increased 1.2 cm2 per week and necrotic tissue decreased by 0.2 cm2 per week. While receiving MDT, these wounds showed remarkable improvement: Necrotic tissue decreased at a rate of 0.8 cm2 per week and total wound surface area decreased by 1.2 cm2 per week (P = .001).
Surveys have also been used to evaluate clinical experiences with MDT.
- In 1935, Robinson 6 polled 600 surgeons about their experiences with MDT; 91.2% responded favorably, while 4.4% responded unfavorably.
- In 2001, Sherman et al 7 reported retrospective data recorded by completion of a questionnaire. The data showed that MDT completely or significantly debrided 17 of 21 wounds of 21 patients treated between 1991 and 1997 who were asked to complete evaluation forms.
The cost-effectiveness of MDT was examined by Wayman et al 8,9 in 2000 and 2001. In 2000, the investigators examined the cost of MDT versus a hydrogel dressing in venous wounds and found that MDT debrided ulcers quickly and was more effective than a hydrogel dressing. The 6 patients treated with maggots in this study achieved complete debridement after only 1 application, while 2 of 6 control group patients required a hydrogel dressings 1 month later. The cost calculations for this study were £78 for MDT and £136 for a hydrogel dressing.
In 2001, the investigators also examined 12 patients with venous ulcers for the average cost to successfully debride 1 leg ulcer. The results showed a cost of £69.53 with MDT, compared with £319.56 with hydrogel dressings.
In 2002, one bottle of maggots cost approximately $70 and could be obtained from the University of California, Irvine, CA.