Maggot Debridement Therapy (MDT)
MDT is the medical use of live, sterile maggots for cleaning non-healing wounds. The use of maggots for this purpose has been noted for centuries even as far back as the Renaissance. Many military physicians used maggots during warfare. They found that soldiers who had their wounds colonized with maggots had a lower mortality rate than those who did not.
Medicinal maggots are approved by the Food and Drug Administration (FDA). They are considered the only living organism allowed for production and marketing. The FDA say they are to be used only "for debriding non-healing necrotic skin and soft tissue wounds, including pressure ulcers, venous stasis ulcers, neuropathic foot ulcers and non-healing traumatic or post surgical wounds.”
Medicinal maggots have three mechanisms of action: debride wounds by dissolving only necrotic, infected tissue; disinfect the wound by killing bacteria; stimulate wound healing. This leads to reduced wound odor, earlier healing, and less pain.
Debriding is a difficult task for physicians because they are not very precise in removing only the necrotic tissue and not healthy tissue. This can create a larger wound, more bleeding than is necessary, and the infection can spread leading to sepsis or amputation of the limb. Using a physician or other means of debriding the tissue creates a longer healing time, and it can be very expensive.
Maggots digest nutrients through extracorporeal digestion where they secrete a broad spectrum of proteolytic enzymes that liquefy necrotic tissue. The maggots then absorb the dead tissue. They start at a size of 1-2mm, and they normally grow to about 8-10mm during the digesting process.
Maggots also disinfect wounds through their antimicrobial secretions. These secretions include allantoin (found in many shaving gels that have a soothing effect on the skin.), urea (used for protein metabolism), phenylacetic acid (used in the production of Penicillin), phenylacetaldehyde(used in perfumes), calcium carbonate (used in teeth cleaning products), and proteolytic enzymes (break down protein into simpler compounds). The bacteria that are not killed by these secretions are ingested and lysed within the maggots. This includes antibiotic resistant forms of bacteria such as Methicillin-resistant Staphylococcus aureus (MRSA).
Maggots promote wound healing in a few different ways. The most obvious is micromassage of the wound by the maggots. This stimulates growth of granulation tissue. The maggot secretions appear to amplify growth healing of epidermal growth factor which is a polypeptide hormone that stimulates cell proliferation especially of epithelial cells by binding to receptor proteins on the cell surface. In addition, they stimulate growth of fibroblasts (gives rise to connective tissue), slow-growing chondrocytes (mature cartilage cells), and cartilage-specific type II collagen (strong, insoluble fibers serving as connective tissue between cells).
Preparation of Maggots
Putrid meat is hung outdoors to attract the wild flies. After eggs are laid in the meat, the meat is transferred to ventilated glass jars until they hatch (8-24 hours). The larvae are fed brewer’s yeast and ground meat for seven days after which they are placed in a jar with clean, warm sand to pupate. The correct species are sorted from the adults.
The flies are placed in a cage with honey, yeast, and water. Temperatures stay in the human comfort range. Gravid female flies begin laying eggs on cubes of meat about a week later. Seven hours afterward, the eggs are washed off the meat into containers. The eggs are disinfected with 10% bleach, and then they are transferred to sterile cultures with a medium of agar, dry meat, and dry yeast. This culture is placed in an incubator at 27 degrees Celsius for 24 hours. Representative maggots from each dish are tested for aerobic and anaerobic microbes. The sterile maggots are shipped in bottles packed in ice.
Application of Wound Dressings
The wound is irrigated with sterile saline, and then a dressing is placed on the border of the wound to protect the skin from the maggots’ enzymes. The maggots are placed on the wound and held in place with nylon mesh. The area is lightly covered in gauze padding and bandaged.
The dressing should be changed daily to check the maggots and the wound. The maggots, however, should be removed every 2-3 days with new maggots being placed depending on the state of the wound (all necrotic tissue should be removed). The maggots need oxygen to survive, so the dressing cannot be anaerobic.
Warning: these pictures are not for people who are grossed out easily.
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