A UK study found that maggots (larval therapy) were no quicker at helping leg ulcers to heal or get rid of bacteria than the standard treatment based on hydrogel, and they were on the whole more painful, although they did speed up removal of dead tissue (debridement).

The study was the work of lead researcher Professor Nicky Cullum, deputy head of health sciences at the University of York, and colleagues also from York and other UK research centres, and is published in the 19 March issue of BMJ.

Although maggots are being increasingly used in wound treatment, there is little evidence of how effective they are compared to other therapies. For this study, Cullum and colleagues compared the clinical effectiveness of larval therapy (maggots) with a standard debridement technique (hydrogel) for sloughy or necrotic leg ulcers.

They recruited 267 patients who were about to be treated for at least one venous or mixed arterial and venous leg ulcer where at least 25 per cent of the tissue had died (become sloughy) and where the ankle brachial pressure index was 0.6 or more (the ratio of the leg blood pressure to the arm blood pressure).

The patients were randomized to receive one of three treatments: maggots comprising loose larvae, maggots comprising bagged larvae, or hydrogel.

The main measure of healing effectiveness was the time it took for the largest ulcer to heal. The researchers also measured the time it took to clear away all the dead tissue, how much bacteria was removed, how much MRSA was in the wound, ulcer related pain, and other variables.

The results showed that:

  • There was little significant difference among the three treatment groups in the time it took for the largest ulcer to heal.
  • The larval therapy was however much quicker at removing dead tissue (debridement) than the hydrogel.
  • Changes in bacterial load with time was much the same in the three groups, as were health related quality of life variables.
  • Although the figures showed no difference between larval therapies and hydrogel in their ability to get rid of MRSA by the end of the debridement phase, there weren’t enough patients with MRSA in the groups for this to be statistically significant (fewer than 7 per cent of patients had MRSA at the start of the period).
  • The mean ulcer-related pain scores were higher in the larval therapy groups than the hydrogel group.

Cullum and colleagues concluded that:

“Larval therapy did not improve the rate of healing of sloughy or necrotic leg ulcers or reduce bacterial load compared with hydrogel but did significantly reduce the time to debridement and increase ulcer pain.”

Cullum told the press that the resurgence in use of maggots for wound healing was premature, reported the BBC.

Although the maggots cleaned the ulcerated tissue more quickly than the hydrogel, they did not speed up healing, she said.

The researchers suggested their findings show there is no real benefit to using maggots compared to the standard hydrogel method.

The only time it might be worth considering would be if it was really important to get the dead tissue cleared away quickly, for instance if someone was having a skin graft.

“Larval therapy for leg ulcers (VenUS II): randomised controlled trial.”
Jo C Dumville, Gill Worthy, J Martin Bland, Nicky Cullum, Christopher Dowson, Cynthia Iglesias, Joanne L Mitchell, E Andrea Nelson, Marta O Soares, David J Torgerson, on behalf of the VenUS II team.
BMJ 2009;338:b773. Published 19 March 2009.
doi: 10.1136/bmj.b773

Click here for Abstract.

Sources: Journal abstract, BBC.

Written by: Catharine Paddock, PhD