Maggot therapy (also known as larval therapy) is a type of
biotherapy involving the introduction of live, disinfected
maggots (fly larvae) into non-healing skin and soft-tissue
wounds of a human or other animal for the purpose of cleaning out the
necrotic (dead) tissue within a wound (
debridement), and disinfection.
There is evidence that maggot therapy may help with wound healing.[1][2]
Medical uses
Maggot therapy improves healing in
chronic ulcers.[1] In
diabetic foot ulcers there is tentative evidence of benefit.[3] A
Cochrane review of methods for the debridement of
venous leg ulcers found maggot therapy to be broadly as effective as most other methods, but the study also noted that the quality of data was poor.[4]
The wound must be of a type that can benefit from the application of maggot therapy. A moist,
exudating wound with sufficient oxygen supply is a prerequisite. Not all wound-types are suitable: wounds which are dry, or open wounds of body cavities do not provide a good environment for maggots to feed. In some cases it may be possible to make a dry wound suitable for larval therapy by moistening it with
saline soaks.[6]
Patients and doctors may find maggots distasteful, although studies have shown that this does not cause patients to refuse the offer of maggot therapy.[7] Maggots can be enclosed in opaque polymer bags to hide them from sight. Dressings must be designed to prevent any maggots from escaping, while allowing air to get to the maggots.[8] Dressings are also designed to minimize the uncomfortable tickling sensation that the maggots often cause.[9]
In maggot therapy, large numbers of small maggots consume necrotic tissue far more precisely than is possible in a normal surgical operation, and can debride a wound in a day or two. The area of a wound's surface is typically increased with the use of maggots due to the undebrided surface not revealing the actual underlying size of the wound. They derive nutrients through a process known as "extracorporeal digestion" by secreting a broad spectrum of proteolytic enzymes[13] that
liquefy necrotic tissue, and absorb the semi-liquid result within a few days. In an optimum wound environment maggots molt twice, increasing in length from about 2 mm to about 10 mm, and in girth, within a period of 48–72 hours by ingesting necrotic tissue, leaving a clean wound free of necrotic tissue when they are removed.[14]
Disinfection
Secretions from maggots believed to have broad-spectrum antimicrobial activity include
allantoin,
urea,
phenylacetic acid,
phenylacetaldehyde,
calcium carbonate, proteolytic enzymes, and many others.[15]In vitro studies have shown that maggots inhibit and destroy a wide range of pathogenic bacteria including
methicillin-resistant Staphylococcus aureus (
MRSA), group A and B streptococci, and
Gram-positive aerobic and anaerobic strains.[16] Other bacteria like Pseudomonas aeruginosa, E. coli or Proteus spp. are not attacked by maggots, and in case of Pseudomonas even the maggots are in danger.[17]
Biology of maggots
Those flies whose larvae feed on dead animals will sometimes lay their eggs on the dead parts (necrotic or gangrenous tissue) of living animals. The infestation by maggots of live animals is called
myiasis. Some maggots will feed only on dead tissue, some only on live tissue, and some on live or dead tissue. The flies used most often for the purpose of maggot therapy are blow flies of the
Calliphoridae: the blow fly species used most commonly is Lucilia sericata, the common green bottle fly. Another important species, Protophormia terraenovae, is also notable for its feeding secretions, which combat infection by Streptococcus pyogenes and S. pneumoniae.[18]
History
Written records have documented that maggots have been used since
antiquity as a wound treatment.[19] There are reports of the use of maggots for wound healing by
Maya, Native Americans, and
Aboriginal tribes in Australia. Maggot treatment was reported in
Renaissance times. Military physicians observed that soldiers whose wounds had become colonized with maggots experienced significantly less morbidity and mortality than soldiers whose wounds had not become colonized. These physicians included
Napoleon's general surgeon, Baron
Dominique Larrey. Larrey reported during the
French campaign in Egypt and Syria (1798–1801) that certain species of fly consumed only dead tissue and helped wounds to heal.[18]
I have frequently seen neglected wounds ... filled with maggots ... as far as my experience extends, these worms eat only dead tissues, and do not injure specifically the well parts."
The first documented therapeutic use of maggots in the United States is credited to a second Confederate medical officer Dr. J.F. Zacharias, who reported during the American Civil War that:
"Maggots in a single day would clean a wound much better than any agents we had at our command ... I am sure I saved many lives by their use."
He recorded a high survival rate in patients he treated with maggots.[20]
During
World War I,
orthopedic surgeon William S. Baer recorded the case of a soldier left for several days on the battlefield who had sustained
compound fractures of the
femur and large flesh wounds. The soldier arrived at the hospital with maggots infesting his wounds but had no fever or other signs of infection and survived his injuries, which would normally have been fatal. After the war, Baer began using maggot therapy at
Boston Children's Hospital in
Massachusetts.[21][22]: 169–71
A survey of
US Army doctors published in 2013 found that 10% of them had used maggot therapy.[25]
Regulation
In January 2004, the FDA granted permission to produce and market maggots for use in humans or animals as a prescription-only medical device for the following indications: "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."[26][27]
Veterinary use
The use of maggots to clean dead tissue from animal wounds is part of
folk medicine in many parts of the world.[28] It is particularly helpful with chronic
osteomyelitis, chronic
ulcers, and other
pus-producing infections that are frequently caused by chafing due to work equipment.[citation needed] Maggot therapy for horses in the United States was re-introduced after a study published in 2003 by veterinarian Dr. Scott Morrison. This therapy is used in horses for conditions such as
osteomyelitis secondary to
laminitis, sub-solar abscesses leading to osteomyelitis, post-surgical treatment of street-nail procedure for puncture wounds infecting the navicular bursa, canker, non-healing ulcers on the
frog, and post-surgical site cleaning for
keratoma removal.[29]
However, there have not been many case studies done with maggot debridement therapy on animals, and as such it can be difficult to accurately assess how successful it is.[30]
^Reames, Mark K.; Christensen, Chris; Luce, Edward A. (1988). "The Use of Maggots in Wound Debridement". Annals of Plastic Surgery. 21 (4): 388–91.
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abSherman, R. A.; Hall, M. J. R.; Thomas, S. (2000). "Medicinal Maggots: An Ancient Remedy for Some Contemporary Afflictions". Annual Review of Entomology. 45: 55–81.
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^Jones, Gemma; Wall, Richard (2008). "Maggot-therapy in veterinary medicine". Research in Veterinary Science. 85 (2): 394–8.
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