Larval Therapy for Chronic Cutaneous Ulcers

Historical Review and Future Perspectives

Edoardo Raposio, MD, PhD, FICS; Sara Bortolini, MSc, PhD; Lara Maistrello, MSc, PhD; and Donato A. Grasso, MSc, PhD

Disclosures

Wounds. 2017;29(12):367-373. 

In This Article

Abstract and Introduction

Abstract

Cutaneous ulcers tend to become chronic and have a profound impact on quality of life. These wounds may become infected and lead to greater morbidity and even mortality. In the past, larvae (ie, maggots) of certain common flies (Lucilia sericata and Lucilia cuprina) were considered useful in ulcer management because they only remove necrotic tissue while promoting healthy tissue in the wound bed, thus helping wounds heal faster. Recently, maggots from several other fly species (Calliphora vicina, Calliphora vomitoria, Phormia regina, Chrysomya albiceps, Sarcophaga carnaria, and Hermetia illucens) have been shown in vitro to possess characteristics (ie, debridement efficacy and putative antimicrobial potentialities) that make them suitable candidates for possible use in clinical practice. This review presents a historical analysis of larval debridement and speculates future directions based on the literature presented.

Introduction

Chronic skin ulcers, such as diabetic ulcers, venous leg ulcers, and pressure ulcers, are increasing in prevalence, representing a costly problem in health care. A rapid rise in the treatment of chronic wounds has been linked to an aging population and an increasing incidence of diabetes and obesity.[1] Leg ulcers are most common, accounting for 43% of skin ulcers.[1] Chronic cutaneous ulcer treatment places a significant burden on the patient and the health care system; in addition, these nonhealing ulcers place the patient at much higher risk for lower extremity amputation.

Treatment of chronic cutaneous ulcers includes a number of different regimens: glycemic control, revascularization, surgery, local wound treatment, offloading, and other nonsurgical treatments. Proper local wound care consists of tissue debridement, control of persistent inflammation or infection, and moisture balance before considering advanced therapies for wounds that are not healing at the expected rate (3 months).

Maggot therapy is a simple and successful method for cleansing infected and necrotic wounds. The use of maggots has become increasingly important in the treatment of nonhealing wounds, particularly those infected with the multidrug-resistant pathogen, methicillin-resistant Staphylococcus aureus (MRSA). Indeed, it has been shown that excretions/secretions from the blowfly Lucilia sericata (LS) exhibit potent, thermally stable, protease-resistant antibacterial activity against in vitro MRSA.[2] The application of sterile LS larvae to an infected nonhealing wound results in the removal of necrotic tissue, disinfection, rapid elimination of infecting microorganisms, and enhancement of the healing process.[3]

Debridement refers to the removal of dead, damaged, or infected tissue to improve the healing potential of the remaining healthy tissue. In order to debride necrotic tissue, larvae (ie, maggots) produce a mixture of proteolytic enzymes, including collagenase, that breaks down the necrotic tissue to a semi-liquid form to be absorbed and digested. Debridement is facilitated by wound disturbance as the larvae crawl around the tissue using their mouthhooks.[4]

Maggot therapy is administered by applying sterilized fly larvae to the wound at a density of 5 to 8 per cm2. To apply larval therapy, a wound-sized hole is cut from a hydrocolloid dressing, a self-adhesive wafer with a semipermeable outer membrane. This both protects the skin from irritation by the maggot's proteolytic enzymes and forms the base of the adhesive dressing. The sterile maggots are then moved from their container to a special piece of nylon netting placed on a nonwoven swab to draw away moisture. The netting is then bunched up to create a cage for the larvae, placed on the wound, and secured to the hydrocolloid dressing by waterproof adhesive tape. The dressing is finally covered with a simple absorbent pad held in place with adhesive tape or a bandage.[3] Maggots are kept over the wound for cycles of about 48 hours; two 48-hour cycles are usually applied each week.

The aim of this paper is to review the history and mechanisms of action of larval therapy while speculating some future directions.

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