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The following is a list of questions about the use of LarvE®, as an aid to those practitioners who are using sterile larvae provided by ZooBiotic Ltd.
These questions and answers can also be downloaded as a pdf document.
What are LarvE?
LarvE is the brand name for sterile larvae of the common green bottle Lucilia sericata that are used in wound management.
What risks are associated with the use of larvae?
A review of the literature has revealed no significant risks or adverse events causally linked with the clinical use of sterile larvae of Lucilia sericata when used as directed. It should always be remembered, however, that larval therapy is a potent therapeutic tool and as such it must be used with caution by staff that have been properly trained in its use.
Can larvae cause wound infections?
The larvae supplied by Zoobiotic Ltd are sterile therefore will not introduce pathogenic organisms into a wound. It is possible, though considered unlikely, that accidental infestations of wounds by larvae could represent a source of infection.
How do LarvE combat wound odour?
Slough and necrotic tissue support the proliferation of proteolytic bacteria. The metabolic processes of these organisms result in the formation of volatile amines that are responsible for the unpleasant smell associated with some types of wounds. By removing the necrotic material and the associated bacteria, the larvae help to reduce or eliminate wound odour.
Can you feel larvae moving in a wound?
Most people are unaware of the presence of larvae within their wound although a small number of patients claim that they can feel them. If full grown larvae are allowed to get onto intact skin surrounding a wound they may tickle. This can easily be prevented by the application of an appropriate dressing system.
Will larvae burrow into healthy tissue?
The larvae of L. sericata will not attack or burrow into healthy tissue although the proteolytic enzymes that they produce can occasionally cause irritation to unprotected skin.
What are the effects of LarvE on wound pain?
Experience suggests that the application of LarvE will sometimes reduce wound-related pain. This is probably due to the elimination of infection, which is responsible for the formation of inflammatory mediators that cause pain in the surrounding tissue.
In some wounds, however, pain may be increased by the presence of larvae, some patients who have leg ulcers with a significant arterial component, complain that their wounds become more painful on the second or third day of therapy. The reason for this is not certain, but it may be associated with pH changes within the wound. In such situations it is recommended that the larvae be removed after two days instead of three, and that the patient's analgesia be reviewed.
What are the effects of LarvE on wound healing?
Over the years, numerous papers have reported that the presence of larvae within a wound appears to promote the formation of granulation tissue. Some support for this observation may be drawn from the work of Prete-1 who demonstrated that larvae' secretions appear to contain an agent that promotes the growth of fibroblast cells in-vitro.
What are the risks associated with the use of LarvE?
A review of the literature has revealed no significant risks or adverse events causally linked with the clinical use of sterile larvae of Lucilia sericata in manner described. It should always be remembered, however, that larval therapy is a potent therapeutic tool and as such it must be used with caution by staff that have been properly trained in its use. Larvae produce very powerful enzymes, which although primarily directed at dead or necrotic tissue, have the potential to cause irritation of healthy tissue if the larvae are applied in excessive numbers or left in place for too long after debridement has been completed. The use of large numbers of larvae in the immediate vicinity of exposed or damaged blood vessels is also probably best avoided
Can LarvE cause wound infections?
LarvE supplied by ZooBiotic Ltd are sterile and therefore will not introduce pathogenic organisms into a wound. It is possible, though considered unlikely, that accidental infestations of wounds by larvae could represent a source of infection.
Will LarvE burrow into healthy tissue?
The larvae of Lucilia sericata will not attack or burrow into healthy tissue although the proteolytic enzymes that they produce can occasionally cause irritation to unprotected skin.
Will LarvE turn into flies within a wound?
It takes about 10-14 days for a newly hatched larva to complete its life cycle and turn into a fly. Dressings should be changed every 3-4 days so the fully grown larvae should be removed well before they are ready to pupate. Furthermore the larvae like somewhere dry and warm to pupate so they will attempt to leave the moist environment of the wound in order to do so.
Will LarvE lay eggs in the wound?
Only adult flies can reproduce or lay eggs.
Can you feel LarvE moving in a wound?
Most people are unaware of their presence, although a small number of patients claim that they can feel them. If full grown larvae are allowed to get onto intact skin surrounding a wound they may tickle but this can be easily prevented by the application of an appropriate dressing system.
Can LarvE be used under compression bandages?
In most instances, the application of a compression bandage should not interfere with the action of LarvE provided they receive sufficient air to breathe.
When should I stop using LarvE?
Most practitioners stop when the wound is clean and free of necrotic tissue, but there is some evidence to suggest that, for chronic wounds, it may be beneficial to continue treatment, possibly with smaller numbers of larvae, until granulation is well established.
Can only hospital patients have treatment with LarvE?
Provided that the patient and their family are in agreement, there is no reason why, with their GP's approval larvae therapy cannot be given to patients in their own home assuming a community nurse is available to undertake the treatment and ensure that waste material etc. is safely disposed of.
Are LarvE available upon prescription?
LarvE can be prescribed by Registered General Practitioners on Form FP10 as an unlicensed medicinal product.
Do I need to 'water' the larvae on a daily basis?
Some practitioners recommend that moist gauze that forms part of the completed dressing should be renewed on a daily basis to prevent larvae from drying out as described previously. Although very young larvae are delicate and susceptible to desiccation, after the first 24 hours they become increasingly resistant to dehydration and generally do not require the application of an additional liquid.
Are there any activities that should be avoided during treatment with larvae?
Patients undergoing treatment with larvae should not immerse their wound in water or sit with the affected area too close to a source of heat, particularly in the first 24 hours after application as there is a possibility that the larvae may dehydrate and die. Care should also be taken when larvae are applied to weight bearing areas such as the feet or buttocks. Ambulant patients receiving therapy on a leg ulcer, for example, may continue to live normally and go about their daily routine as usual.
Are there published papers available to support the use if larvae?
Over 60 papers have been published that described the use of LarvE, details of which are available upon request from Zoobiotic Ltd.
What is the ethical position relating to the use of larvae?
The use of larvae in wound management has a sound basis in literature. It appears to be free of any serious or significant side effects, and may have major advantages over conventional treatments for certain types of wounds. Provided that a specific patient has no objection to the use of larvae there appear to be no ethical barriers to their use.
Do I have to count the larvae into and out of the wound?
Some practitioners have suggested that larvae should be counted into and out of a wound to ensure that they have all been removed. This is totally unnecessary and virtually impossible to do. Furthermore, it is not uncommon for a proportion of the larvae that applied to a wound to fail to survive. This means that, even if it were possible count large numbers of larvae into a wound, (an almost impossible task), this number would not correlate with the number of full grown larvae that were recovered after several days treatment.
Do I need to `water' the larvae on a daily basis?
Some practitioners recommend that the "moistened gauze" that forms part of the completed dressing should be renewed on a daily basis to prevent the larvae from drying out as described previously. Although very young larvae are quite delicate and susceptible to desiccation, after about the first 24 hours they become much more resistant to dehydration and generally do not require the application of any additional liquid.
How long should larvae be left on the wound?
It is normally recommended that LarvE should be left on the wound for three days, although they are sometimes changed after two days if the wound is painful, or left for four days if pain is not a problem and there are large quantities of slough present.
Are there any activities that should be avoided during treatment with LarvE?
Patients undergoing treatment with LarvE should not immerse their wound in water or sit with the affected area too close to a source of heat, particularly in the first 24 hours after application as there is a possibility that the larvae might dry out and die. Care should also be taken when larvae are applied to weight bearing areas such as the feet or buttocks. Ambulant patients receiving larvae therapy on a leg ulcer, for example, may continue to live normally and go about their daily business as usual.
Are there any special precautions or drug interactions with LarvE treatment?
There have been no reports of adverse interactions between larvae treatment and any form of medication, although it is recommended that patients receiving anticoagulant therapy should be carefully monitored during treatment. It has been shown that larvae are unaffected by antibiotics at the concentration that occur in blood and tissue fluid-2 and studies carried out by the BRU have shown that they are also unaffected by X-rays.
It has been shown that larvae are adversely affected by the presence in wounds of hydrogel residues containing propylene glycol as a preservative-3 so it is important to remove all such gels prior to the application of LarvE.
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.
What if some larvae are left in the wound after treatment?
In the unlikely event that some larvae will remain undetected within the depths of a wound, these will certainly be found the next time the dressing is removed. The larvae will not pupate within the wound and therefore cannot turn into flies.
How do I dispose of larvae that have been removed from a wound?
In hospital it is recommended that larvae and the associated dressing residues be double-bagged in the appropriate clinical waste bags and sent for disposal in the usual manner. In the community the LarvE brand of sterile larvae are supplied in a container that has been approved for the transportation of clinical waste. This may be used to transport used larvae and associated dressing residues to an approved disposal facility.
Incineration is the preferred method, but if this is not possible the bags may be disposed of in accordance with local practice. If the bags are not incinerated, and the larvae complete their life cycle and turn into flies, these will soon die within the plastic bags. Given the fact that wild green bottles normally lay eggs on carrion, it is not considered that flies that develop from larvae removed from wounds will represent an additional health hazard. ZooBiotic Ltd also provides an approved disposal container with each batch of larvae supplied.
