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Larval therapy

VIEW PRODUCTS: Larval therapy

Larval therapy is primarily used to debride slough and necrosis (dead tissue) from acute or chronic wounds, remove bacteria and stimulate healing. It can also be used to ascertain the extent of a wound through removing devitalised tissue.

The larvae produce a proteolytic enzyme that destroys necrotic tissue, which they then ingest. The larvae only ingest dead tissue, slough and cellular debris (Fleischmann et al, 2004). This leaves viable tissue intact and can lead to improved healing — it has also been postulated that ‘micro-massage’ of the wound by the movement of the larvae can stimulate the formation of granulation tissue and exudate (wound fluid) (Namias et al, 2000).

Larvae can be applied free-range, where they are kept in place with a dressing but allowed to ‘roam’ freely over the wound seeking out areas of necrosis, or supplied in ‘bio-bags’, where the larvae are contained within a mesh pouch or bag. Healthy tissue is not affected by maggots, although the enzymes that they produce can result in exacerbation of maceration (Acton, 2007).

Larvae can remain in place on a wound from 3–5 days, although it may be necessary to change any secondary dressings more frequently due to the build-up of exudate (Pyatt, 2011).

What kind of wounds should a larval dressing be used on?

Larval therapy is most commonly used to debride chronic leg ulcers (Pyatt, 2011), but can also be used on any type of wound that contains necrotic material, regardless of aetiology (Jones and Thomas, 2000), including:

  • Pressure ulcers
  • Infected wounds
  • Surgical wounds
  • Dehisced wounds (where sutures have burst and the wound edges have separated)
  • Diabetic ulcers
  • Malignant wounds.
  • Amputation sites

There a number of larval products available – how can I choose the correct one?

Each patient will have different wound care needs that need to be considered when choosing the right product – the following questions will help with dressing selection.

Does the wound need to be debrided?

Debridement is the main purpose of larval therapy, as they liquefy and ingest dead tissue. This can help to clean the wound, remove bacteria and allow healthcare professionals to better assess the extent of the wound.

Note: It is also important to notify patients that the wound may appear to enlarge initially due debridement, as slough and necrosis is removed.

Are you concerned about infection?

Larvae will actually help to reduce infection within a wound, as any bacteria are ingested with liquefied necrotic tissue. The bacteria are destroyed as they pass through the larvae’s digestive system (Thomas et al, 1999).

Is the patient in pain?

In patients already experiencing wound pain before starting larval therapy, there may be some discomfort during the treatment, due to exposed nerve endings, for example. This usually occurs when the maggots are large enough to be felt moving against those nerves (approximately 24 hours after starting treatment). Once the dressings are removed, any larvae-related pain should stop immediately.

What will happen to wound exudate during larval therapy?

The use of larval therapy can actually stimulate exudate production in a wound due to the activity of the larvae and the liquefying of dead tissue (Pyatt, 2011).

What about the ‘yuck’ factor?

Patients can find the idea of larval therapy off-putting and even disgusting. Therefore, it is important to keep them informed at all times, especially regarding common misconceptions that the maggots will ‘burrow’ into their flesh (larvae do not ingest healthy tissue [Acton, 2007]), or that the larvae may reproduce in the wound (impossible as the larvae are not mature). 

Points to remember when applying a larval dressing

For larvae to function effectively they require a moist environment.

Larval therapy should not be used in patients on anticoagulants as it can increase bleeding (Pyatt, 2011).

Pain relief should also be considered, as in some patients larval therapy can cause discomfort.

It is also important to thoroughly cleanse the wound before the application of larval therapy, as this will clear out residue from other treatments that may harm the larvae.

When should a larval dressing not be used?

The efficacy/safety of larval therapy has yet to be established in the following circumstances:

  • Dry, necrotic wounds
  • Fistulae
  • Wounds connecting with abdominal cavities or organs
  • Wounds that might bleed easily
  • Wounds with poor blood supply.

Cost-effectiveness

Although cost-effectiveness is important, choosing the cheapest dressing is not necessarily the best thing to do, as dressing choice should always be guided by the patient’s needs. If a dressing fails to perform well, more frequent dressing changes will be needed incurring greater nursing time. 

Patient choice

Patient choice and preference should always be considered. This helps to build up a good nursing–patient relationship and is in line with national policy.

Performance indicators

  • Antimicrobial
  • Debridement

References

Acton C (2007) A know-how guide to using larval therapy for wound debridement. Wound Essentials 2: 156–9

Fleischmann MD, Grassberger M, Sherman R (2004) Maggot Therapy: a handbook of maggot-assisted therapy. Thieme, New York

Jones M, Thomas S (2000). Larval Therapy. Nurs Standard 14(20): 47–51

Namias N, Varela JE, Varas RP, Quintana O, Ward CG (2000) A case report of maggot therapy for limb salvage after fourth-degree burns. J Burn Care Rehab 21(3): 254–7

Pyatt V (2011) The use of larval therapy in modern wound care. Wounds International. Available online.

Thomas S, Andrews A, Hay P, Bourgoise S (1999) The antimicrobial activity of maggot secretions: results of a preliminary study. J Tissue Viability 9(6): 127–32