As summarised in the accompanying article, larval debridement therapy (LDT) experienced a boom in the early part of the 20th century when it was introduced for the treatment of osteomyelitis

The use of larvae subsequently fell out of favour following the introduction of antibiotics, but clinical interest was rekindled with the emergence of drug-resistant microbes that resulted in problem wound infections[1,2].

Currently, the efficacy of blowfly larvae as reliable, selective debriders is well-known and they are in routine clinical use at a number of wound-healing centres across the world. There are essentially no contraindications to their use, although aggressive surgical debridement should always be employed first in cases of rapidly evolving life- or limb-threatening infections.

In a practice focused on lower extremity limb salvage in the diabetic, renal failure and angiopathic populations, the struggle faced by surgeons is how to reliably determine the adequate level of surgical debridement, while still leaving maximal limb length for reconstruction or a functional amputation. The strategy of sequentially removing all non-viable or infected material with multiple conservative debridements in the operating room must be weighed against cost and the heightened risk incurred by undertaking such procedures on patients with serious medical comorbidities.

In this setting, larval therapy may prove beneficial for two purposes. Firstly, their primary current use is to allow nonoperative debridement on patients for whom surgery represents too great a risk. An additional role is to assist in determining the proper (reliable) level of amputation by selectively debriding all nonviable tissue, leaving only healthy tissue behind to be used in creating a definitive, stable surgical closure. While prospective, controlled trials and cost-effeciency comparisons have yet to be performed, it is hoped that earlier and more routine use of larvae may provide substantial savings to the patient in terms of hospital days (LDT can be performed as an outpatient treatment), operating room costs, anaesthetic exposures, and tissue loss.
 
The major barriers to the wider adoption of LDT in the US are logistical. Unlike in European countries, systems do not exist to arrange for the application of LDT in the home or outpatient setting, where it is most cost-effective. Dressings are a specific difficulty, particularly for large or complex wounds, because contained 'net-pouch' larvae are not available on the US market, meaning that patients and community nurses would have to deal with the unruliness of 'free range' larvae, which are prone to escape.

Undoubtedly, the way to drive more widespread adoption of LDT and pave the way for more organised home and outpatient therapy is to clinically prove the effectiveness and cost-savings benefit of LDT for specific indications. A laudable, but isolated, effort in this regard was the VenUS II randomised controlled trial comparing the clinical effectiveness of larval therapy with hydrogels for sloughy or necrotic venous leg ulcers[3]. Although the trial found no significant difference in the rate of healing or cost-effectiveness[4] between LDT and control groups, it did note a significantly reduced time to debridement for LDT. Commentators noted that LDT would never be expected to heal venous ulcers when used in place of compression, since larvae do not address the underlying wound-generating pathophysiology of venous incompetence[5].

These results emphasise that larval therapy is not a panacea for all wounds, but is an effective means of low-risk debridement. In the future, research should, therefore, focus on wounds that stand to benefit from ultra-selective debridement (such as where limb salvage is at stake), or those that fail to heal despite optimisation of all underlying medical conditions and adequate wound bed preparation. Two interesting examples of the latter are recalcitrant infections involving bone or orthopaedic hardware.

As more recognition is given to the role played by bacterial biofilms in the maintenance of these antibiotic-resistant infections, laboratory researchers have already begun to investigate whether larval excretions and secretions are effective in removing biofilm from alloplastic materials, with initially promising results[6-10].
 
In summary, the current major use of LDT in our practice is to selectively debride necrotic or infected tissue from patients who are too sick to undergo anaesthesia and surgical debridement. Reports from the literature have indicated that they are also applied to augment healing in various types of wounds such as diabetic foot ulcers, pressure necrosis wounds, or venous stasis ulcers, often with ill-defined indications. In order to increase the use of larvae in current wound care and limb salvage treatment, it will be necessary to prove their usefulness and cost-effectiveness for specific indications using well-designed, prospective trials.

Past and current literature trends suggest that promising starting points may include:

• Selective debridement to determine the proper level of amputation in limb salvage
• Treatment of infection by antibiotic-resistant bacteria
• Treatment of osteomyelitis
• Removal of biofilm from chronically infected wounds, bones, and orthopaedic hardware. 

Click here to see The use of larval therapy in modern wound care

References

1. Sherman RA. Maggot versus conservative debridement therapy for the treatment of pressure ulcers. Wound Repair Regen 2002; 10(4): 208-14.
2. Pechter EA, Sherman RA. Maggot therapy: The surgical metamorphosis. Plast Reconstr Surg 1983; 72(4): 567-70.
3. Dumville JC, Worthy G, Bland JM, et al. Larval therapy for leg ulcers (Venus II): randomised controlled trial. BMJ. 2009; 338: b773.
4. Soares MO, Iglesias CP, Bland JM, et al. Cost effectiveness analysis of larval therapy for leg ulcers. BMJ 2009; 338: b825.
5. Ternhag A. Larval therapy for leg ulcers. Compression may be key. BMJ 2009; 338: b2064.
6. Cazander G, van de Veerdonk MC, Vandenbroucke-Grauls CM, Schreurs MW, Jukema GN. Maggot excretions inhibit biofilm formation on biomaterials. Clin Orthop Relat Res 2010; 468: 2789-96.
7. van der Plas MJ, Dambrot C, Dogterom-Ballering HC, Kruithof S, van Dissel JT, Nibbering PH. Combinations of maggot excretions/secretions and antibiotics are effective against Staphylococcus aureus biofilms and the bacteria derived therefrom. J Antimicrob Chemother. 2010; 65: 917-23.
8. Cazander G, van Veen KE, Bouwman LH, Bernards AT, Jukema GN. The influence of maggot excretions on PAO1 biofilm formation on different biomaterials. Clin Orthop Relat Res 2009; 467: 536-45.
9. Harris LG, Bexfield A, Nigam Y, Rohde H, Ratcliffe NA, Mack D. Disruption of staphylococcus epidermidis biofilms by medicinal maggot Lucilia sericata excretions/secretions. Int J Artif Organs 2009; 32: 555-64.
10. van der Plas MJ, Jukema GN, Wai SW, et al. Maggot excretions/secretions are differentially effective against biofilms of Staphylococcus aureus and Pseudomonas aeruginosa. J Antimicrob Chemother 2008; 61: 117-22.