Teabags filled with maggots that heal chronic wounds
Chronic wounds are a major health problem that affect hundreds of thousands every year, and many end up having an amputation as a result. But now a company in Wales thinks it has the answer: teabags filled with tiny maggots. it sounds stomach-churning, but the reality is that these small pouches are manufactured in an industrial setting not dissimilar to a hospital isolation unit.
The pouches are innocuous, looking and feeling like a soggy teabag.
chronic wounds are defined as wounds that take more than six weeks to heal, and include foot and leg ulcers and bed sores.
Those affected tend to have poor circulation — poor oxygen and blood supply to wounds slows down the healing process.
Delayed healing can lead to infections, and eventually amputation — every year over 2,000 people have a limb amputated because of a chronic wound.
normally, wound healing starts with red blood cells moving in to form a blood clot, stopping any bleeding and sealing the wound. Then white blood cells kill off any infectious substances that entered while the wound was exposed.
next, collagen, a protein that strengthens tissue by forming a ‘scaffold’, is delivered to replace lost tissue; the outer skin layers can then start contracting and close the wound completely.
The problem with chronic wounds is that the area is full of dead tissue, which impedes the healing process and so needs to be removed. The cleaning process is known as debridement.
‘A chronic wound will have a mixture of new tissue and scar tissue and slough, which can impair healing, so we need to debride chronic wounds before healing can happen,’ says Michael Gaunt, a consultant vascular surgeon at the Spire Lea hospital in cambridge.
The body will try to rid itself of this dead tissue in a slow process called autolytic debridement, where it releases moisture to soften the useless tissue and wash it away, but this is not always effective in large wounds.
There are number of debridement techniques, including surgical, where a doctor will scrape out dead tissue with a scalpel, or use special highpressure washes, chemicals or ultrasound to remove it.
But these carry risks such as removing the healthy tissue, and need expert training.
MAny chronic wounds require treatment with a combination of different kinds of debridement techniques. Maggot therapy, or larval therapy, is another wound-cleaning option. it was first applied medically in World War i, after surgeons realised that soldiers whose wounds became infested with maggots healed faster, and so they put maggots into wounds intentionally. There are huge advantages to larval therapy, says Duncan Stang, a podiatrist and the national diabetes foot co-ordinator for Scotland at hairmyres hospital in East Kilbride.
‘Debridement requires a high level of expertise and understanding of the underlying structures to ensure no unwanted tissue damage,’ he says. Many practitioners debriding wounds will be podiatrists or tissue viability nurses and a high level of training and expertise is required.
Larval therapy is more convenient and offers more specific debridement as the maggots only target dead or infected tissue, Mr Stang adds. The maggots, specifically of the greenbottle fly, one of the most common species in Britain, especially in the summer, release special chemicals — enzymes — into the wound, which soften the dead tissue into a liquid that they then drink.
The maggots have teeth-like structures at the front of their bodies which they use to hold on to their food source and scour the surface to know when to release their enzymes.
Traditionally maggots are applied directly into a chronic wound, where they have free rein to circulate. They are still widely used this way in the nhS, where they are kept on for three to four days to clean wounds, and then removed before they start developing into flies (maggots transform at roughly seven to ten days old). once removed, they can be replaced with new maggots if needed. A limitation of course is that you cannot stop free maggots from travelling beyond the wound, and although they only feed on dead tissue, they are sometimes lost by the end of the treatment. The maggots can’t be felt as they are so small and often in places with nerves that do not work properly.
A2013 study in the British Journal of community nursing concluded that maggot therapy is effective and can help to prevent admission to hospital for surgical debridement.
however, doctors and patients can be too squeamish to use it. This is where the maggot teabags could come in.
The technology was developed by BioMonde, a spin-off from the Bro Morgannwg nhS Trust in South Wales. A warehouse in Bridgend houses roughly 36,000 flies at a time to breed for twiceweekly egg collection, where small tubes with a mesh lid are put inside the fly boxes (similar to plastic storage tubs).
Each tube contains a special protein which the flies detect as food and they then lay their eggs on top of the mesh.
These eggs are then chemically disinfected to kill off bacteria on their surface and processed for 24 hours before they hatch into tiny maggots. Then they are counted into vials, with different sized vials for the different sized ‘teabags’ (called Biobags).
Saline is added to keep them alive until they are used. The bags are sealed, ready for delivery the next day to hospitals, health centres or district nurses.
Biobags, which cost between £200 and £300 each (compared with £150-£200 for the same number of free larvae), are sent in a box with an ice pack and must be used within a day as the maggots would die without food.
Betty Storey, a 55-year-old customer services advisor in northern ireland had the Biobag applied to her foot wound last year. She has a history of psoriasis on her hands and feet which causes the skin to crack. in october 2014, the skin on her foot cracked open into a gaping 20cm by 10cm wound from her foot to her knee. She was treated with antibiotics to clear the infection, then had Biobags to clear remove black dead tissue which was preventing healing.
‘it was extremely distressing to see the extent of the depth of tissue damage,’ she says. After ten days of larval therapy, which included two Biobags and free larvae to finish off, the wound looked ‘incredible’, she says.
‘The bagged larvae did most of the work, while the free larvae were applied after to successfully debride the wound edges,’ she adds, describing the sensation as a mild ‘tickling’.
Betty was given special pressure bandages to help the wound close — it’s now just 2.5cm by 1.5cm.
The Biobag comes in five sizes, with a standardised number of maggots inside — the smallest is 2.5cm by 4cm and contains 50 maggots, the largest is 10cm by 10cm, with 400.
The ratio is based on the company’s calculations of the most efficient maggot activity, which is five to seven maggots per square centimetre — any more and the maggots become less efficient as there is insufficient food (dead tissue) to keep them all active, so they just go to sleep.
DESpiTE Betty Storey’s experience, patients are unlikely to feel the maggots moving because they are small and do not physically eat the tissue, says Mr Gaunt. Any wiggling felt is likely to be psychosomatic. The Biobag feels wet to the touch, but there is not movement — although you can see the maggots wiggling.
To apply the Biobag, surrounding skin is first protected with a cream because feeding larvae will create moisture and waterlogged skin could become macerated, explains Mr Stang. Dressings and bandages hold the bag in place.
The maggots start off a few millimetres in length, smaller than a grain of rice, and after the standard four-day treatment, they are roughly 50 times bigger, but no bigger than a pea.
They won’t turn into flies because they are removed after four days. Also, wounds are often wet, and maggots need a dry, dark spot to pupate. once used, the bags are disposed as clinical waste.
Mr Stang has now swapped from free larvae therapy to the bagged version at his practice.
‘patients don’t always like having free larvae on their legs, and it can be a long process as we have to physically count each maggot going in and out to ensure none have gone AWoL,’ adds Mr Gaunt. ‘Bagged maggots cannot go missing and it will make larval therapy more acceptable to patients and more controllable.’