How Can Maggots Save Limbs?

By Akanksha Singh, BDSReviewed by Sophia Coveney

Introduction
What is Maggot Therapy?
Mechanism of Action
Administration of Maggot Therapy
Applications of Maggot Therapy
Application in Diabetic Foot Ulcers
Conclusion
References
Further readings

Maggot therapy has been used in the field of medicine since ancient times. It was popularized during the world wars due to frequent soldier injuries. Despite the patients’ reluctance in using this therapy, it has been gaining momentum largely due to recent advancements that have solved its shortcomings.

What is maggot therapy?

Maggot Debridement Therapy (MDT) or Larval therapy is a type of biotherapy or biosurgery where live disinfected maggots are placed on a wound with the intention of debriding necrotic tissues. The most widely used maggot for this treatment is the larvae of the greenbottle blowfly (Lucilia sericata). Maggot debridement therapy is indicated when the wound is infected with bacteria that are resistant to antibiotics and non-healing wounds. Amputations of limbs can be prevented when treated with maggot therapy.

Mechanism of action

The maggots debride necrotic tissues by secreting a variety of proteolytic enzymes, one being collagenase. Collagenase disintegrates the necrotic tissues of the wound to a semi-liquid state. Then this semi-liquid state can be easily digested following absorption. The maggots use their mouth hooks to crawl around the wound tissues which causes wound disturbance leading to debridement.

It has been discovered by scientists that maggots produce antibiotic-like agents. The chemical produced by them has a broad-spectrum bactericidal effect. Their antibacterial ability is a part of their self-defense mechanism. Additionally, maggots ingest and eliminate microorganisms present in the wound as a part of their normal feeding process.

Furthermore, to curb bacterial proliferation they generate and release ammonia that turns the wound alkaline. When tested in vitro, live maggots had the ability to kill or contain the proliferation of several types of bacteria. They are especially effective against Staphylococcus aureus and Group A and B streptococci. They are moderately effective against Pseudomonas species but did not kill or inhibit the growth of the Escherichia coli or Proteus spp.

Researchers have also identified some growth-promoting substances in the maggot secretions. These substances induce wound healing by promoting the migration of fibroblasts into the wound. The presence of fibroblasts in the wound aid in tissue regeneration. These combined actions of the medicinal maggot produce a cleaned healed wound.

Administration of maggot therapy

The maggots are introduced to the wound in a dressing. The base of the hydrocolloid dressing is self-adhesive and has a semi-permeable outer layer that protects the skin from irritation from the maggot’s proteolytic enzymes. The dose for this therapy is 5-10 larvae per square centimeter of the wound. The sterile maggots are left in the wound within a nylon netting for about 48-72 hours, after which they are removed.   

Applications of maggot therapy

Maggot therapy is indicated when a traumatic wound does not heal. Some of these are diabetic ulcers, vascular ulcers, venous stasis leg ulcers, neurovascular ulcers, pressure ulcers as well as perineal gangrene, florid necrotizing fasciitis, and osteomyelitis. Additionally, this therapy is also used on burns and wound infections post-surgery. It palliates certain types of tumors and fungating lesions. Maggot therapy is also used for malignant wounds which cannot be treated through surgery because the patient has comorbidities or if the anatomical location of the wound is not accessible. Maggots have also been an option for treatment along with antibiotics for superficial infections that have an aggressive nature.

 When these wounds are treated with maggots they decrease by 4.1 cm over 14 days as compared to the wounds only treated with a dressing. Furthermore, there is a decrease in necrotic tissues by 33% over 30 days. With maggot therapy, the wounds heal faster, and the wound odor and exudate are low when compared to dressing alone.

Although effective for most traumatic wounds, maggot therapy is contraindicated for wounds that have proximity to organs and blood vessels. It is also contraindicated for septic patients.

Application in diabetic foot ulcers

Maggot therapy has been effective in the treatment of diabetic foot ulcers. A controlled cohort study was done with 18 diabetic patients who had neuropathic non-healing leg wounds. Their wounds were treated with maggot therapy. When compared with the control group maggot therapy proved to be better at debridement and even showed faster growth of granulation tissue as well as wound epithelialization.

According to another study, when the ischemic foot wounds were treated with maggots the patients needed fewer days of administration of antibiotics. Additionally, maggot-treated wounds healed 4 weeks faster compared to the control group.

Maggot therapy plays an essential role in the salvaging of limbs. Usually, this treatment is used as a last resort. It has been determined by studies that pre-amputation maggot therapy has been responsible for saving 40-50% of limbs.

 Researchers suggest that the factors behind these high rates of limb salvage are due to increased fibroblast migration, advancement of granulation tissue, and better oxygen perfusion that are associated with the mechanism of action of maggot therapy.

Conclusion

This amputation sparing treatment has been hailed by surgeons and researchers alike for its wound debridement and elimination of infection properties. Maggot therapy’s several advantages overtake the patients’ unwillingness to use this treatment.

Although there is a need for more randomized control trials. The applications of maggot therapy can be widened with more research. It is a promising treatment and there should be an increased awareness among medical practitioners to incorporate maggot therapy early on in treatment.

References

• Whitaker, I. S., et al. (2007). Larval therapy from antiquity to the present day: mechanisms of action, clinical applications and future potential. Postgraduate medical journal, 83(980), 409–413. https://doi.org/10.1136/pgmj.2006.055905
• G. N. Jukema, et al (2002) Amputation-Sparing Treatment by Nature: “Surgical” Maggots Revisited, Clinical Infectious Diseases, Volume 35, Issue 12, Pages 1566–1571, https://doi.org/10.1086/344904
• Sherman R. A. (2009). Maggot therapy takes us back to the future of wound care: new and improved maggot therapy for the 21st century. Journal of diabetes science and technology, 3(2), 336–344. https://doi.org/10.1177/193229680900300215
• Nishijima, A., et al. (2017). Maggot debridement therapy for a patient with critical limb ischaemia and severe cardiac dysfunction: possibility of limb salvage. Case reports in plastic surgery & hand surgery, 4(1), 42–47. https://doi.org/10.1080/23320885.2017.1327322