Maggots
Scientific Name(s): Lucilia cuprina, Lucilia sericata, Phaenicia sericata
Common Name(s): Botfly maggot, Fly larva, Grub, Living antiseptic, Maggot, Surgical maggot, Viable antiseptic
Medically reviewed by Drugs.com. Last updated on Oct 30, 2023.
Clinical Overview
Use
Maggot debridement therapy (MDT) is used in persistent ulcers, especially pressure ulcers and diabetic-related ulcers, although other wound applications have been reported. Cost effectiveness of the therapy, as well as effectiveness in reducing time to heal, has not been established.
Dosing
Standards for the growth and harvesting of P. sericata larvae have been published, and have been accepted by the Food and Drug Administration (FDA) in the approval of maggots in the medical management of wounds. Estimates of the quantity of maggots required for debridement include the use of 10 maggots per cm2 of wound and 100 maggots per 50 g necrotic tissue over 4 days.
Contraindications
Contraindications may include life- or limb-threatening conditions, lack of wound hemostasis, deep-tracking wounds, psychological issues, and hypersensitivity. With wounds, contraindications may only exist until underlying pathology is addressed (ie, maggots have been successful in osteomyelitis and limb-threatening conditions).
Pregnancy/Lactation
Information regarding safety and efficacy in pregnancy and lactation is lacking.
Interactions
None well documented.
Adverse Reactions
When used therapeutically, maggots do not appear harmful to living tissues, but can produce pain and pruritus, as well as anxiety. Severe bleeding has resulted from maggot therapy.
Toxicology
Information regarding the toxicology of maggot exudate is limited.
Biology
Maggots are the larvae of various flies. The species P. sericata (green blow fly) has been therapeutically used with success for many decades, but other species such as Lucilia caesar, Phormia regina, and Musca domestica have also been used.Claxton 2003, Li 2009 Standards for the growth and harvesting of P. sericata larvae have been published and have been accepted by the FDA for approval in the medical management of wounds. The second instar (stage) larvae are used to feed on tissue material before they develop into nonfeeding pupae after 5 to 7 days. These are removed before they enter the 1- to 3-week–long pupation stage leading to adult flies.Claxton 2003, FDA 2010, Sherman 2002, Sherman 1996
History
The effects of maggots on wounds have been known since the 1500s when it was observed that maggots cleaned untreated wounds, removing necrotic tissue without apparent harm to living tissue. Later, some military surgeons noticed that maggot-infested wounds responded better than noninfested wounds. The first scientific paper on the surgical use of maggots appeared in 1931, and interest in the technique continued throughout the 1930s and early 1940s. MDT was routinely performed in over 300 hospitals during this time. The first civilian use, based on observations during World War I, was in treating 4 children with osteomyelitis who did not respond to other available treatments. Subsequent occurrence of tetanus in other cases led to the development of bacteriologically sterile maggots. Early uses for maggot therapy included the treatment of abscesses, burns, cellulitis, gangrene, and ulcers. The use of maggots declined rapidly in the mid-1940s with the development of antibiotic drugs, but more recent cost-effectiveness evaluations and acceptability studies suggest a resurgence in interest.Claxton 2003, McKeever 2008, Mumcuoglu 1999, Sherman 2002
Uses and Pharmacology
Forensic entomology
Analyses of maggots found in decomposing bodies can reveal information about the time of death and the presence of specific drugs, as well as providing clues about crime location and circumstances.(Beyer 1980)
Wound debridement
The mechanisms by which maggots debride wounds and thereby promote healing have not been proven conclusively. However, a variety of mechanisms have been suggested, and studies are being undertaken to elucidate specific mechanisms. The exudate produced in response to the maggots physically washes bacteria out of the wound. The crawling larvae mechanically stimulate viable tissues to rapidly produce granulation tissue. They also enzymatically liquefy necrotic tissue. Bacteria are destroyed within the alimentary tracts of the larvae, which also use necrotic tissue as food. Maggots may produce antibacterial agents that are released in their secretions. They also increase the alkalinity of the wound, promoting healthy granulation. Substances proposed as beneficial secretions of maggots include allantoin, ammonium ions, and calcium carbonate.(Claxton 2003, Horobin 2005, Mumcuoglu 1999) Upregulation of endothelial cell activity has also been reported.(Sun 2016)
Antibacterial action of the secretions of maggots has been determined and may include methicillin-resistant Staphylococcus aureus and Pseudomomas aeruginosa.(Bexfield 2004, Cazander 2009, Steenvoorde 2004, van der Plas 2008)
Clinical data
Numerous case reports and anecdotal evidence exist. A few prospective studies have been published among a limited pool of researchers, including those pursuing FDA approval of medical maggots, and even fewer randomized clinical trials have been undertaken.
In a prospective, but not randomized, study of MDT versus conventional therapy for pressure ulcers, positive findings were attributed to MDT. Reductions in wound size, time for debridement, and amount of necrotic tissue, as well as increases in granulation outcomes all reached statistically significant differences in the 61 wounds (50 patients) evaluated.(Sherman 2002) Other measures such as decreased odor from necrotic tissue and decreased wound pain were demonstrated for MDT in a similar prospective study evaluating pressure ulcers and chronic leg ulcers secondary to diabetes.(Mumcuoglu 1999) Additionally, a reduction in the need for dressing changes has been reported. (Mudge)
A randomized clinical trial evaluated the cost-effectiveness of MDT in leg ulcers.(Soares 2009) Therapy with maggots was estimated to incur costs similar to those of the standard hydrogel treatment. Additionally, only slightly faster healing and greater general acceptance was found for MDT, with statistical significance not being attained.(Soares 2009) A similar randomized trial (the VenUS II Trial) found time-to-healing did not differ between MDT and hydrogel; however, time-to-debridement was significantly faster for larval therapy versus hydrogel. Patient selection for inclusion in the trial may have influenced the study outcomes.(Dumville 2009) Similar findings (increased debridement but similar healing rates) have been reported in other clinical trials.(Davies 2015, Opletalova 2012)
Granulation and angiogenesis in diabetic foot wounds has been reporetd in a clinical study evaluating maggot debridement therapy.(Sun 2016) Maggot therapy demonstrated significant reductions compared to controls in both S. aureus (P=0.047) and P. aeruginosa (P=0.048) in foot ulcers of diabetics in a randomized, placebo-controlled trial (N=50).(Malekian 2019)
Conflicting data exist for the relative efficacy of contained (in a bag or pouch) versus free-range larvae.(Blake 2007, Steenvoorde 2005)
Other case reports include reviews of the treatment of wounds secondary to arthroscopy, MDT in palliative and outpatient settings, and in patients with hemophilia or diabetes.(Frykberg 2006, Rojo 2004, Sherman 2001, Steenvoorde 2007, Wollina 2005)
Some patients with severe tissue destruction may also receive antibiotics along with MDT. A report evaluates this combination. Larvae survival was decreased when very high doses of gentamicin and cefazolin were administered. Antibiotics showing no effect on survival rate included ampicillin, ceftizoxime, clindamycin, mezlocillin, and vancomycin.(Sherman 1995)
Other uses
L. cuprina maggot excretion/secretions have demonstrated antiviral and virucidal activity against Rift Valley Fever and Coxsackie B4 viruses in vitro with a 5% and 26% reduction in viruses, respectively. Virucidal activity was also observed against the Coxsackie B4 virus after a 24-hour incubation time.(Abdel-Samad 2019)
The saliva and hemolymph from L. sericata maggots have been shown to both have leishmanicidal activity against Leishmania tropica in vitro.(Rahimi 2021)
Dosing
Estimates of the quantity of maggots required for the use of debridement includeBlake 2007, Claxton 2003, Sherman 2002 the use of 10 maggots per cm2 of woundClaxton 2003 and 100 maggots per 50 g necrotic tissue over 4 days.Blake 2007
In a trial evaluating loose maggots versus contained (bagged) maggots, the time for most efficient consumption of necrotic tissue was determined to be 4 days, in contrast to usual protocol regarding dressing changes.Blake 2007 Mean time-to-debridement in prospective studies of pressure ulcers suggests applications of maggots required 10 days to 3 weeks, depending on wound size and extent of necrosis.Sherman 2002, Mumcuoglu 1999
Pregnancy / Lactation
Information regarding safety and efficacy in pregnancy and lactation is lacking.
Interactions
None well documented.
Adverse Reactions
Myiasis, the infestation of tissue with fly larvae, is a recognized ICD-10 disease, but is distinct from the therapeutic application of larvae discussed in this monograph.Sherman 2005
Pain, commonly associated with the end stage of treatment when healthy tissue has been exposed, has been reported and managed with analgesia.Mumcuoglu 1999, Soares 2009 Pruritus and discomfort, as well as anxiety have also been reported in a minority of patients; however, the incidence of reported adverse events may be a reflection of the type of wound and depend upon the (self-selecting) patient.Sherman 2002, Teich 1986
Case reports of serious bleeding exist. Contraindications may include life- or limb-threatening conditions, deep-tracking wounds, lack of wound hemostasis, psychological issues, and hypersensitivity. With wounds, contraindications may only exist until the underlying pathology is addressed (ie, maggots have been successful in osteomyelitis and limb-threatening conditions).Claxton 2003, Sherman 2002, Stockley 1982, Steenvoorde 2008
Toxicology
Information regarding the toxicology of maggot exudate is limited.
References
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