Protocol for the use of sterile maggots in wound management

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                    Larval therapy is widely used by healthcare practitioners
                    throughout the United Kingdom for the management of infected
                    or necrotic wounds.
                    The benefits of this treatment are well documented and have
                    been widely published in the medical and nursing press.
                    This document, which contains practical advice on the use of
                    larvae, has been produced to assist existing or potential users of
                    larvae develop a nursing protocol for larval therapy in their own
                    The text may be edited freely by users of LarvE for this

                    The information contained in this draft protocol is believed to be
                    accurate and reflect current best practice but no responsibility
                    can be accepted by the ZooBiotic Ltd for any information that
                    may appear in any modified version of this publication.

                    ZooBiotic Ltd

Nursing Protocol Aug 2007 ver 1.04                  Page 1 of 15                   TJ13082007A
                                     NURSING PROTOCOL
                             WOUND MANAGEMENT

                                         Produced by …..

                                 Hospital/Trust Name/Locality Name


                                             Date of preparation

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                    Larval therapy is widely used by healthcare practitioners
                    throughout the United Kingdom for the management of infected,
                    sloughy or necrotic wounds.
                    The benefits of this treatment are well documented and have
                    been widely published in the medical and nursing press.
                    This document summarises the procedures that should be
                    followed in ----------------------------------Trust when using larval

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                 PROCEDURE                                                 RATIONALE

   Assessing the wound and patient
   Wounds that can be treated with larvae
   Larval therapy has been used to treat most types of
   infected, sloughy or necrotic wounds, irrespective of        It makes no difference to larvae what causes a wound.
   aetiology. Examples of wounds that have been treated         It will feed on any dead tissue present.
   with larvae include leg ulcers, pressure ulcers, infected
   surgical wounds, malignant wounds and diabetic

   Wounds that are not generally suitable for larvae
   Dry necrotic wounds ( these require softening first),
   fistulae, wounds that bleed easily, wounds close to          The efficacy and/or safety of larvae has not been
   major blood vessels or nerves and any situations where       demonstrated in these wound types.
   the blood supply is insufficient to permit healing to
   take place.

   Larvae should not be applied to patients with clotting
   disorders, or individuals receiving anticoagulant
   therapy unless they are under constant medical
   supervision in a healthcare facility.

   Things to monitor during larvae therapy                      Exudate is increased because the larvae liquefy the
   Exudate production is often increased during larvae          dead tissue in the wound. This also leads to a
   therapy, and there is sometimes an initial increase in       temporary increase in odour formation.
   wound odour. This is only temporary and usually
   resolves after the first dressing change.

   Sometimes patients with ischemic wounds complain of          Pain is thought to result from changes in wound pH.
   increased wound pain during treatment. Management
   of pain is easier when utilising the Biofoam dressing.

   Analgesia can be used.

   If in doubt seek a second opinion or contact your
   Tissue Viability Nurse

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   Prior to ordering the Larvae
   Determine the number of larvae required
   Assess the size of the area to be treated and determine      The number of larvae required will be determined by
   the number of larvae to be applied. Experience has           the size and condition of the wound. One container of
   shown that it is more cost effective to use large            LarvE will generally be sufficient for wounds
   numbers of larvae for one or two treatment cycles than       measuring up to 5 cm x 5 cm. Larger wounds may
   smaller numbers for an extended period. A simple             require two or more pots to effect debridement.
   ‘calculator’ that may be used to help determine the
   number of pots required is available on the ZooBiotic
   website (, and a laminated printed
   version is available upon request.

   ‘Free range’ larvae or BioFOAM™ Dressings?
   Larvae are available in two forms. ‘Free-range’ larvae
   are applied directly to the wound, and allowed to roam
   freely over the surface seeking out areas of slough or
   necrotic tissue.

   A second presentation is available in which larvae are       The precise nature of the dressing system selected will
   applied contained in a BioFOAM dressing, in which            be determined by the size and location of the area to be
   the larvae are enclosed in net pouches containing            treated. Correct selection will facilitate a secure
   pieces of hydrophilic polyurethane foam, that are            dressing and prevent larvae escaping from the wound
   placed directly upon the wound surface.                      environment.

   Although ‘free range’ larvae offer a clinical advantage
   on deep wounds where undermining or a sinus is
   present, the ease of application and removal of the
   BioFOAM Dressing makes these dressings the product
   of choice for most users of sterile larvae both in the
   Primary and Secondary Healthcare sectors.

   Type of retention system required
   For free-range larvae, one of the following will be

   Nylon Net Dressing - for wounds that are isolated and
   easy to dress, available in a variety of sizes.

   Nylon Net Sleeve - (open at both ends) for extensive
   or circumferential limb wounds (arms or legs).

   Nylon Net Boot – for extensive wounds on limb
   extremities (feet, hands, stumps etc.).

   Half Boot – for toes.

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   Ordering sterile larvae
                                                                  ZooBiotic Ltd is the principal supplier of sterile larvae
   Sterile larvae (LarvE) can be ordered by telephone or          in the UK. When placing an order, provide details of
   fax from ZooBiotic Ltd at the address shown at the end         the delivery address, the number of larvae required, the
   of this document during working hours from Monday              date and time of delivery and the address to which the
   to Friday.                                                     invoice should be sent.

   Larve must be prescribed by a medical doctor.

   It is recommended that orders be placed through either
   the hospital or community pharmacy

   Orders received by12 Noon for BioFOAM Dressings
   and by 2.30 pm for loose larvae can be dispatched by
   courier for delivery the following day.

   Storing sterile larvae
   Larvae should be used on the day of delivery; the
   expiry date on the packaging will be this date.                Keeping the larvae cool, but not too cold, prolongs
   Normally larvae should be used within 8 hours of               their life and ensures that they are at their most active
   delivery. Store in a fridge until usage.                       when applied to the wound.

   If larvae are stored in a fridge, it is recommended that       The optimum temperature for larvae storage is between
   they be allowed to return to room temperature before           8° - 10° C.

   Application of sterile larvae
   Larval therapy should only be undertaken by an                 This is important to maintain appropriate standards of
   individual who has previous practical experience in the        care.
   management of wounds, and a thorough understanding
   of the wound healing process.

   Prior training in practical aspects of the technique is
   desirable although not essential as detailed instructions
   are available from ZooBiotic Ltd who may also be
   contacted by telephone for additional information or
   assistance from their experienced clinical staff.

   This can be done both during normal office hours on
   the main contact number 0845 2301810, and via the
   Clinical Helpline for Healthcare Professionals on 0845
   2306806, at all other times.

   Items required for performing a

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   dressing for free range larvae
   Prepare a dressing trolley containing the following             The dressings selected will be determined by the size
   items:                                                          and location of the area to be treated, but for a simple
      LarvE pack containing one or more vials of sterile          procedure, these items will generally suffice.
       larvae, a tube of sterile saline and a nylon net
       dressing, boot or sleeve
      A hydrocolloid sheet dressing or a roll of zinc
       paste bandage
      A sterile dressing pack or wound cleansing pack
      Pair of sterile scissors
      A roll of waterproof adhesive tape 2.5cm wide e.g.
      A perforated plastic film dressing such as Melolin,
       Telfa Release or Interpose
      An absorbent dressing pad
      A roll of adhesive tape (Micropore or equivalent)
      A lightweight retention bandage if appropriate
      Yellow bag

   Preparation of larvae
   Add to the container of larvae about 5 ml of sterile            This releases all the larvae from the top and side wall
   saline, which is equivalent to a depth of about 1-2 cm          of the container into the solution. Accumulating all the
   in the bottom of the container, and gently agitate the          larvae in a single container in this way speeds up and
   container. If more than one pot of larvae is to be              facilitates the process of application.
   applied, pour the contents of this first container into the
   second and agitate as before. Repeat this process as
   many times as necessary.

   Preparation of dressing trolley
                                                                   The contents of the larvae container are sterile and this
   Open the dressing pack and related materials and                will ensure that asepsis is maintained.
   layout on a dressing trolley, or other suitable surface,
   using an aseptic technique.

   Ensure the patient is positioned comfortably and in a           This is to reassure the patient and address any concerns
   suitable position for the dressing to be applied and that       that they might have.
   they fully understand all aspects of the treatment.

   Application of larvae using standard

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   Preparation of the wound site
   Remove any existing dressing and clean the wound to            Some dressing residues, for example hydrogels that
   remove any dressing residues.                                  contain propylene glycol, may inhibit larvae
   Cut a hole in a hydrocolloid sheet the size and shape of
   the wound and place securely onto the surrounding              This protects the peri-wound skin and forms a layer
   skin. Alternatively cut strips of hydrocolloid dressing        upon which to attach the nylon net.
   and place around the wound.

   If the wound is relatively small and of limited depth, a       This gives the larvae room to develop and prevents
   double layer of hydrocolloid may be applied to form a          them from being squashed.
   shallow chamber into which the larvae are introduced.

   If a hydrocolloid dressing cannot be used, the skin
   surrounding the wound may be protected with strips of          Some patients react badly to hydrocolloid dressings so
   a bandage impregnated with zinc paste.                         alternative ways of protecting the skin must be
   Removing larvae from their container
   Slowly pour the saline containing the larvae onto a
   piece of sterile nylon net (LarvE Net) that is supplied
   with each container of LarvE . The net should be               When the saline containing the larvae is poured out
   placed upon a sterile gauze swab and pre-moistened             onto the net in this way, the liquid is immediately
   with saline to overcome surface tension effects. If the        drawn away through the net by the swab, leaving the
   larvae are poured out too quickly, the saline (and some        larvae in a heap on the surface.
   of the larvae) may run off the net onto the surrounding

   Applying larvae to a wound
   Invert the sterile nylon net over the wound and tape
   securely to the hydrocolloid sheet using a waterproof
   adhesive tape such as Sleek. The larvae will not fall         This effectively forms an enclosure that prevents the
   off the net when it is inverted, as they will be held in       larvae from escaping onto the surrounding skin.
   place by surface tension.

   If a zinc paste bandage is used in place of the
   hydrocolloid sheet, press the nylon mesh firmly down
   into the paste and apply a further layer of bandage            This will provide a secure larvae dressing for patients
   around the edges to anchor the net in position.                for whom hydrocolloid dressings are contraindicated.

   The central part of the net must remain un-occluded in
   order to permit free drainage of exudate and allow the
   larvae to obtain an adequate supply of oxygen.                 If this is not done the young larvae may die.

   Completing the dressing
   Apply a swab moistened with sterile saline over the
   outside of the net and cover with a dressing with a
   perforated plastic film wound contact layer such as
   Release, Melolin or Telfa.                                     The young hatchlings are quite delicate and need to be

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                 PROCEDURE                                               RATIONALE

                                                              kept moist.
   Complete the dressing with an absorbent pad held in
   place with tape or a bandage as appropriate. Occlusive
   dressings or film dressings SHOULD NOT be used, as
   these will cause the larvae to suffocate.

   Any unused larvae should be disposed of, as they can
   no longer be considered sterile.

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                 PROCEDURE                                                   RATIONALE

   Application of larvae using a LarvE boot
   or half boot.
                                                                 These are easier to apply than the standard dressing
   For an extensive wound on the foot, a net boot is
                                                                 and provide a more effective method of preventing the
   available. Smaller boots (half-boots) are available for
                                                                 larvae from escaping.
   the dressing of necrotic toes.

   When using the boot, place a ‘collar’ or ring of
                                                                 The collar should be applied in two overlapping pieces
   hydrocolloid dressing around the limb above the
                                                                 without excessive tension to prevent any possible
   wound. Ensure the hydrocolloid is in pieces, to allow
                                                                 tourniquet effect.
   for any swelling of the limb.

   Apply the boot over the limb and fix the open end to
   the hydrocolloid ring using waterproof adhesive tape.

   Areas of healthy skin enclosed within the net boot
                                                                 This is to protect the intact skin from the action of the
   should be protected with a piece of hydrocolloid, a thin
                                                                 larvae’s enzymes.
   layer of zinc paste or white soft paraffin, or some other
   bland skin preparation. Alternatively a proprietary skin
   protective agent may be used.

   When using the boot system, instead of pouring the
                                                                 The larvae will adhere to the wet material, removing
   larvae out onto a piece of net or into the bag prior to
                                                                 them from the swab.
   application, pour the larvae onto a moistened non-
   woven gauze swab and gently wipe the swab over the
   wound surface.
                                                                 See ‘Completing the dressing’ in the previous section
   Apply a suitable outer dressing as described
                                                                 on page 8

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                 PROCEDURE                                                    RATIONALE

   Application of larvae using a LarvE

   For extensive or circumferential wounds on the leg, a          This technique allows large areas to be dressed whilst
   net sleeve, open at both ends, can be slid into place          ensuring that the larvae are contained within the
   over the affected area and sealed to strips of                 wound, and allows for expansion of the dressing if
   hydrocolloid formed into collars, placed above and             swelling occurs.
   below the margins of the wound.

   When using this technique, slide the net into position,        This is the easiest way of applying the sleeve without
   fix to the upper collar and push up the lower part of the      scraping the larvae off the wound surface.
   net to expose the wound.

   Protect the healthy skin enclosed within the sleeve as         See ‘Application of larvae using a LarvE boot or half
   previously described, and apply the larvae to the              boot’ on page 9
   wound using a swab as described above.

   Once the larvae are in place, slide the open end of the
   sleeve down over the wound and fix to the second
   hydrocolloid collar.
                                                                  See ‘Completing the dressing’ in a previous section on
   Apply the outer dressing as described previously               page 8

   Application of LarvE BioFOAM
                                                                  Some dressing residues such as some hydrogels may
   Before applying LarvE BioFOAM Dressings to the
                                                                  contain propylene-glyco, which may inhibit larvae
   wound, it is recommended that any existing dressing
   residues are thoroughly removed and the wound
                                                                  Larvae secretions have been shown to excoriate
   It is advisable to protect the surrounding skin from
   excoriation with a proprietary skin protectant i.e. Zinc
   based ointment or impregnated bandage, cavalon etc.
                                                                  As the larvae are confined within the net pouch they
   Sudocream is provided with the dressing.
                                                                  are unable to ‘roam’ freely over the surface of the
                                                                  wound. In certain circumstances the BioFOAM
   Remove the BioFOAM Dressings from the transit
                                                                  Dressings may be moved around the wound if
   containers and place directly on the surface of the

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                 PROCEDURE                                                RATIONALE

   wound. Repeat using as many BioFOAM Dressings as           required.
   necessary to cover the area to be cleansed.

                                                              As the non-viable tissue is liquefied, exudate levels
   Complete the dressing with an absorbent pad held in        will increase.
   place with tape or bandage as appropriate. Occlusive
   dressings SHOULD NOT be used as these will cause
   the larvae to suffocate

   Dispose of any unused BioFOAM Dressings.

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                 PROCEDURE                                                 RATIONALE

   Daily evaluation, aftercare and duration
   of treatment
   Check the outer bandages, absorbent padding and
                                                               This maintains the comfort and dignity of the patient
   gauze on a daily basis and change if they become
                                                               and prevents the outer dressing from becoming
   excessively wet or malodorous.
                                                               saturated, which could adversely effect larvae growth.
   Larvae should be left on a wound for up to 5 days.
                                                               This will ensure that the larvae perform optimally.
   If pain becomes a problem increasing the patient’s
   analgesia may be an option.

   Utilising the Biofoam dressing enables better pain
   management as the larve enzymes can be irrigated
   away and the dressing replaced without the need to
   discontinue treatment.

   Removal of larvae from a wound
   Removal of larvae is a simple process.

   Loose Larvae
   First position a clinical waste disposal bag (yellow        This is to catch any larvae that fall out of the wound.
   bag) under the wound.

   Depending upon the location and size of the wound,
   remove the net retention dressing with or without the       It is generally easier to remove the hydrocolloid and
   hydrocolloid frame, and gently remove the larvae with       net in one piece.
   a gloved hand or a pair of forceps.

   Any larvae that have found their way into the depths of
   a wound will generally come to the surface if the           They have to come to the surface to breathe.
   wound is irrigated with a stream of sterile water or

   Larvae will not pupate or turn into flies within a wound
   and they cannot multiply or ‘breed’. If further larvae
   are to be applied, it does not matter if a few individual
   larvae are missed, as these will easily be retrieved at
   the time of the next dressing change by which time
   they should be fully grown.

   BioFOAM Dressings
   Remove outer absorbent padding then remove
   BioFOAM Dressing(s) and place in clinical waste bag.

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   Reassessment of the wound
   When all the larvae have been removed, reassess the          If full debridement has been facilitated larvae are
   wound to see if further larval therapy is required or        normally no longer required.
   whether a change to conventional therapy is indicated.

   The disposal of larvae removed from
                                                                This normally involves placing them in clinical waste
   Provided an aseptic procedure is used, the larvae
                                                                bags, which should be sealed and sent for destruction
   supplied by ZooBiotic Ltd are sterile up to the time
                                                                in the usual way.
   that they are introduced onto the wound.

   As soon as they come into contact with tissue or body
   fluid, however, they must be regarded as potentially
   contaminated, and therefore must be disposed of as any
   other type of dressing residue or clinical waste in
   accordance with the local control of infection policy.

   For users in the community where disposal may be
   difficult, special containers are provided for
   transporting and disposal of larvae.

   On the death of a patient
   If a patient dies unexpectedly during larval therapy, the    This is to respect the dignity of the patient and the
   larvae should be removed from the wound prior to the         sensitivities of the family.
   transfer of the patient to the mortuary, and disposed of
   as described above.

   Special Precautions

   If the patient is on anti-coagulant therapy, close           This is to ensure that if a bleed occurs immediate and
   monitoring of the patient is advised.                        appropriate action can be taken.

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For further information on any aspect of larval therapy contact:

ZooBiotic Ltd.
Units 2-4 Dunraven Business Park
Coychurch Road
CF31 3AP
Tel 0845 2301810
Fax 01656 668047

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Description: Protocol for the use of sterile maggots in wound management