Maggots as Healers: The Increasing Use of Maggot Debridement Therapy
by K.B.
Zoology 444
University of Wahsington
Summer 2000
Abstract
Since the 1 500's, clinicians have observed the beneficial effects of maggots on human
necrotic tissue. However, until the late 20th century, the use of maggots in necrotic wound
treatment was never fully explored due to the advent of antibiotics and aseptic techniques.
But along with the increasing use of antibiotics has come the increase in antibiotic resistance
and thus the need for "new" treatments in wound therapy. The last 20 years have seen a
tremendous increase in the study and resultant application of maggot therapy to treat necrotic
wounds. As maggot therapy increases in use, the benefits and results become even more
astounding.
Introduction
The use and popularity of maggot debridement therapy (MDT) is currently increasing
worldwide. MDT, larval therapy (LT) and biosurgery all refer to the use of fly larvae for the
treatment of necrotic wounds. MDT can be used to treat leg ulcers, osteomyelitis (bone
infections), abscesses, and carbuncles, limb salvage after severe burns and chronic or acutely
infected wounds. MDT enjoyed a brief period of popularity during the 1920's-1940's before
its resurgence in popularity began again in the 1980's. The end of the twentieth century
ushered in a tremendous increase in antibiotic resistance as well as an increasing acceptance
of natural or "alternative" healing. These factors influenced the recognition of a need for
alternative approaches to healing, and MDT became a suitable option for necrotic wound
therapy.
Traditional thought about maggots revolves around an identification of maggots with death
and decay. The fact that their association with decay is now being used to promote healing
and new life is extraordinary. As modern medicine continues to search for alternative forms
of healing necrotic wounds to replace ineffective drugs and inefficient treatments it appears
that maggot therapy will continue to be modified into an acceptable, and possibly,
mainstream treatment option. The success of this treatment has tremendous implications for
nontraditional medicine in modern medicine and the recognition of future possibilities for the
use of entomology in human medicine. The question that remains is, is maggot therapy
proficient enough at wound healing to ask patients to forego other treatment options and
allow their bodies to be infested with such a "repulsive" organism as a maggot?
Results
History and Early Techniques of MDT
Documentation of the use of MDT exists from as early as the 1500's when Ambroise Pare
reported on the healthy appearance of wounds sustained by soldiers in the field (Reames et
al., 1988). The first recorded intentional use of MDT in the United States was during the
Civil War (1860's) by the Confederate surgeon J.F. Zacharias (Sherman et al., 2000). The
wounds healed successfully, however the soldiers sustained Clostridium perfringens and
Clostridium tetani infections as a result of the treatment. In 1920, William Baer, the "founder
of modern maggot therapy" (Sherman et al., 2000), developed a means of sterilizing the
maggots used for treatment, thereby reducing the number of infections and increasing the
efficacy of the treatment. By the 1930's maggot therapy was being used throughout the
country, although mainstream use was limited because of the cost of the maggots and the
time required preparing maggot dressings. As a result of antibiotic introduction,
improvements in wound care, aseptic techniques and surgical techniques, by the 1940's
maggot therapy became virtually obsolete (Sherman et al., 2000).
According to Sherman et al., early techniques in MDT involved the placement of maggots
directly upon the wound. The maggots were held in place by specially constructed dressings
composed of layers of crinoline, gauze or copper mesh and held in place by adhesive tape.
The dressings were cumbersome and often uncomfortable to the patient. Glass or metal
devices were developed to allow for wound drainage and access by the physician to the
feeding maggots. Up to 600 maggots were sometimes used for an extensive injury (Sherman
does not explain the relativity of "extensive"). Fly eggs were sterilized with Dakin's solution
and formaldehyde after attempts at larvae sterilization failed to kill Clostridium species.
Biology of MDT
MDT is a controlled form of human myiasis in which an appropriate myiasis inducing
Diptera (fly) species is introduced to a necrotic tissue in an effort to harvest the beneficial
effects of human myiasis. Myiasis is defined as "the infestation of live human and vertebrate
animals with dipterous larvae, which, at least for a certain period, feed on the host's dead or
living tissue, liquid body substances, or ingested food" (Sherman et al., 2000).
Maggot debridement therapy can be accomplished by two families of Diptera (flies);
Calliphoridae and Sarcophagidae. Sherman et al. reports that facultative calliphorids are the
most efficient in MDT. According to Sherman et al., the biological factors which make
calliphorid larvae the most suitable include their rapid larval development within the hosts,
their broad range of suitable hosts, the ease in which they are reared in vitro, the ease in
which their eggs can be sterilized and the fact that they generally do not invade internal
organs. The most popular species used in MDT is the greenbottle blowfly, Lucilia sericata.
Courtenay et al. (2000), Church (1996) and Namias et al. (2000) also endorse the use of
sericata, while Reames et al. (1588) found Phormia regina to be effective as well. The
primary factor that determines a fly's efficacy in treatment is its ability to induce myiasis in
the tissue without damaging the surrounding living, healthy tissue of the wound. There are
some species of Calliphoridae that cannot be used for MDT, as they are truly parasitic and
will feed on living tissue. Also, while flies of the family Oestridae are known to cause human
myiasis, they are not used medically because they are obligate parasites with a high degree of
host specificity (Sherman et al., 2000).
Why Does Maggot Therapy Work?
The benefits of maggot therapy on wounds are threefold; debridement (elimination) of
necrotic tissue, wound disinfection through microbial killing and promotion of wound
healing (Sherman et al., 2000). Debridement occurs when the feeding maggot introduces
proteolytic enzymes into the wounds and the liquefied tissue in ingested. Other enzymes
secreted by the maggots have antimicrobial properties that promote disinfection of the
wound. Ammonia secreted by the maggots makes the wound more alkaline which in turn
discourages microbial growth as well. While the maggots crawl over the wound they
introduce urea, ammonium bicarbonate, allantonin and a mixture of calcium carbonate with
picric acid into the disturbed tissue. These substances promote wound healing, and have been
shown to heal wounds when used as an alternative to live maggots (Sherman et al., 2000).
Sherman et al. failed to explain why these substances have such tremendous healing
properties. An inclusion of those factors would add to the impact of the benefits of MDT.
Present Applications and Techniques
MDT is currently being used in the United States and in the United Kingdom to treat nonacute external wounds that have failed at least one course of conventional treatment
(Sherman et al., 2000). Dressings consist of hydrocolloid pads that prevent the maggot's
proteolytic enzymes from interacting with healthy tissue and also protect the patient from
sensing the movement of the larvae. The maggots are placed on the wound and covered by a
sterile sheet of nylon mesh and the pad. Absorbent pads cover the top of the dressing to
capture wound exudate. In general, 5-10 larvae per cm2 are used for treatment and removed
24-72 hours after being placed on the wound. The treatment can either be performed as an
outpatient or inpatient therapy depending on the severity of the wound and patient comfort
with the treatment.
MDT: One Success Story
As MDT has risen in popularity there have been numerous applications in wound healing.
One particular example occurred in a study done by Namias et al. in which MDT was used to
salvage limbs following bilateral lower extremity fourth degree burns (Namias et al., 2000).
MDT was proposed as a last resort treatment for a 41-year-old male who had previously
undergone numerous attempts at wound debridement, skin autografting and hyperbaric
oxygen therapy for the burn wounds that covered 9% of his total body surface area. The
larvae of the greenbottle blowfly, Phaenicia (Lucilia) sericata were placed on the wounds
four times, each for a total of three days. Nylon stockings covered the 2-mm long maggots
during each 48-72 hour treatment. After the fourth treatment, the wounds were completely
free of necrotic tissue and the wounds were 90% closed. The remaining holes around each
ankle were treated by with surgical soft tissue coverage. This is just one example of the
tremendous capability and usefulness of MDT when all other traditional treatment options
have been exhausted.
Discussion
Sherman et al. provide a complete, well-written account on the use, efficiency and benefits of
MDT. I feel that my understanding of MDT would have been heightened by a more
conclusive discussion of the biochemical elements of maggots in MDT. Since the article was
contained in an entomological journal, I think more discussion of the how the biology of
maggots determines their use would have been appropriate.
I am interested to see how MDT continues to develop. It appears from the literature that there
are virtually no risks in using MDT as long as proper techniques are maintained and the
benefits are astounding. In an age of medicine in which it is painfully obvious that drugs and
conventional surgery have been severely abused, treatments such as MDT are a refreshing
and viable alternative to traditional medicine.
More research needs to be done on species that may or may not be particularly suited to
different types of wounds and tissue treatment. Also, the overall image of maggot therapy
must be improved in order for it to become accepted as a mainstream therapy. It is difficult
for the general public to see maggots as anything but horrid, filthy creatures and this image
must be wiped clean for MDT to continue to enjoy the rising popularity of today.
The fact that some of the substances excreted by maggots into necrotic tissue contain such
benef~cial antimicrobial and healing properties should continue to be explored. It may be
that these chemicals can simply be used on their own without having to use the maggots
along with them. The general public would more likely accept this form of treatment.
References
Church, J.C.T. 1996. The traditional use of maggots in wound healing, and the development
of larva therapy (biosurgery) in modern medicine. J. Alt. Compl. Med. 2(4):525-527
Courtenay, M., Church, J.C.T., and Ryan, T.J. 2000. Larva therapy in wound management. J.
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Graner, J.L. 1997. S.K. Livingston and the maggot therapy of wounds. Mil. Med. 162
(4):296-300
Namias, N., Varela, J. E., Varas, R., Quintana, O., and Ward, C.G. 2000. Biodebridement: A
case report of maggot therapy for limb salvage after fourth-degree burns. J. Burn Care
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